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May 14, 2002 Macro Languages AoPL, S'02 Macro Languages Claus Brabrand Michael I. Schwartzbach BRICS, University of Aarhus, Denmark
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May 14, 2002 Macro Languages AoPL, S'02 Outline Introduction Macro survey: Lexical macros: CPP, M4, T E X, ( Dylan ) Syntax macros: C++ templates, Scheme, JTS, MS 2 The macro language Metamorphic syntax macros Next week: The metafront Tool Specificity parsing Language transformation
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May 14, 2002 Macro Languages AoPL, S'02 Introduction
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May 14, 2002 Macro Languages AoPL, S'02 “Macro” Webster’s(“macro”) = Main Entry: 2 macro Pronunciation: 'ma-(")krO Function: noun Inflected Form(s): plural macros Etymology: short for macroinstruction Date: 1959 “a single computer instruction that stands for a sequence of operations”
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May 14, 2002 Macro Languages AoPL, S'02 Motivation (#1) Abstraction (language extension): Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } foreach (String s in list) { System.out.println(s); } foreach (String s in list) { System.out.println(s); } vs.
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May 14, 2002 Macro Languages AoPL, S'02 Motivation (#2) Genericity (uniform abstraction mechanism): Generic abstraction mechanism for all syntactic categories: …whereas functions only “take” and “give” expressions: ( ) Principle of Abstraction: “Any semantically meaningful syntactic class can in principle be used as the body of an abstraction” - Robert Tennent, 1981 Principle of Abstraction: “Any semantically meaningful syntactic class can in principle be used as the body of an abstraction” - Robert Tennent, 1981
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May 14, 2002 Macro Languages AoPL, S'02 Motivation (#3) Consistency: Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } vs.
![May 14, 2002 Macro Languages AoPL, S 02 Motivation (#3) Consistency: Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } vs.](http://images.slideplayer.com./16/5168193/slides/slide_7.jpg "May 14, 2002 Macro Languages AoPL, S 02 Motivation (#3) Consistency: Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Object[] strings = list.toArray(); for (int i=0; i<strings.length; i++) { String s = (String) strings[i]; System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } vs.")
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May 14, 2002 Macro Languages AoPL, S'02 Motivation (#4) Laziness (abbreviation): vs. Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } foreach (String s in list) { System.out.println(s); } foreach (String s in list) { System.out.println(s); }
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May 14, 2002 Macro Languages AoPL, S'02 Motivation (#5) Encapsulation (hide complexity): vs. foreach (String s in list) { System.out.println(s); } foreach (String s in list) { System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); } Iterator iterator = list.iterator(); while (iterator.hasNext()) { String s = (String) iterator.next(); System.out.println(s); }
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May 14, 2002 Macro Languages AoPL, S'02 Macro Survey
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May 14, 2002 Macro Languages AoPL, S'02 Many Macro Languages CPP M4 TEXTEX Scheme C++ templates MS 2...and many more Dylan JTS
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May 14, 2002 Macro Languages AoPL, S'02 Non-Alphabetical Characters CPP M4 TEXTEX Scheme C++ templates MS 2...and many more Dylan JTS
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May 14, 2002 Macro Languages AoPL, S'02 Level of Operation CPP M4 TEXTEX Scheme C++ templates Dylan JTS LexicalSyntactic...and many more MS 2
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macros Operate on token sequences: M LEX : (T OKEN S EQ ) n T OKEN S EQ Precede actual compilation (conceptually) –i.e. a preprocessor Independent of host language syntax Languages: CPP:“The C Preprocessor” M4: “The Unix Macro Preprocessor” TEX: TEX’s macro mechanism Dylan: Dylan’s macro mechanism (hybrid)
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): #define square(X) X * X
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): #define square(X) X * X square(z + 1) #define square(X) X * X square(z + 1) ()z + 1square
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): #define square(X) X * X square(z + 1) => z + 1 * z + 1 #define square(X) X * X square(z + 1) => z + 1 * z + 1 ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): Work-around: Explicitly add parentheses #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) (X) * (X) ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): Work-around: Explicitly add parentheses #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1) #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1) ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macro Example Square (CPP): Work-around: Explicitly add parentheses –Problem: Independent of host language syntax Unsafe: parse errors discovered at invocation-time #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) X * X square(z + 1) => z +(1 * z)+ 1 #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1) #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1) ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 Syntactic Macros Operate on abstract syntax trees: M SYN : (A ST ) n A ST Integrated with host language –typed with host language nonterminals Languages: C++: The C++ template mechanism Scheme: Scheme’s define-syntax mechanism JTS:“Jakarta Tool Suite” macro mechanism MS 2 : “Meta Syntactic Macro System” : The macro language
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May 14, 2002 Macro Languages AoPL, S'02 Syntactic Macro Example Square ( ): macro square ( ) ::= { * } macro square ( ) ::= { * }
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May 14, 2002 Macro Languages AoPL, S'02 Syntactic Macro Example Square ( ): * * exp E exp E macro square ( ) ::= { * } macro square ( ) ::= { * } ~
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May 14, 2002 Macro Languages AoPL, S'02 Syntactic Macro Example Square ( ): * * exp E exp E y + 1y + 1 y + 1y + 1 exp macro square ( ) ::= { * } macro square ( ) ::= { * } square( ) ~
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May 14, 2002 Macro Languages AoPL, S'02 Syntactic Macro Example Square ( ): * * exp E exp E * * exp y + 1y + 1 y + 1y + 1 y + 1y + 1 y + 1y + 1 E exp E y + 1y + 1 y + 1y + 1 exp macro square ( ) ::= { * } macro square ( ) ::= { * } square( ) => ~
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May 14, 2002 Macro Languages AoPL, S'02 Lexical Macros CPP, M4, T E X, (Dylan) ()z + 1 * => square
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May 14, 2002 Macro Languages AoPL, S'02 CPP CPP (“The C Preprocessor”): Also as a stand-alone expander: gcc –E program cpp program Intercepts preprocessor directives “ # ”: #define, #undef, #ifdef, #if, #include, #line, ##, … #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1) #define square(X) (X) * (X) square(z + 1) => (z + 1)*(z + 1)
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax #define swap(X,Y) { int t=X; X=Y; Y=t; }
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0;
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; *** test.c:3: parse error before ‘else’
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; *** test.c:3: parse error before ‘else’
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; *** test.c:3: parse error before ‘else’ #define swap(X,Y) do { int t=X; X=Y; Y=t; } while(0) if (a>b) swap(a,b); else b = 0; #define swap(X,Y) do { int t=X; X=Y; Y=t; } while(0) if (a>b) swap(a,b); else b = 0;
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May 14, 2002 Macro Languages AoPL, S'02 Fixed Invocation Syntax –Problem: fixed invocation syntax same for exp, stm, … M(x,y,z) #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; #define swap(X,Y) { int t=X; X=Y; Y=t; } if (a>b) swap(a,b); else b = 0; *** test.c:3: parse error before ‘else’ #define swap(X,Y) do { int t=X; X=Y; Y=t; } while(0) if (a>b) swap(a,b); else b = 0; #define swap(X,Y) do { int t=X; X=Y; Y=t; } while(0) if (a>b) swap(a,b); else b = 0;
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May 14, 2002 Macro Languages AoPL, S'02 Body Expansion Consider: #define A 87 #define B A #undef A #define A 42 B => ??? #define A 87 #define B A #undef A #define A 42 B => ???
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May 14, 2002 Macro Languages AoPL, S'02 Body Expansion Consider: Eager expansion (definition-time): #define A 87 #define B A #undef A #define A 42 B => ??? #define A 87 #define B A #undef A #define A 42 B => ??? B => 87
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May 14, 2002 Macro Languages AoPL, S'02 Body Expansion Consider: Eager expansion (definition-time): Lazy expansion (invocation-time): #define A 87 #define B A #undef A #define A 42 B => ??? #define A 87 #define B A #undef A #define A 42 B => ??? B => 87 B => A CPP
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May 14, 2002 Macro Languages AoPL, S'02 Body Expansion Consider: Eager expansion (definition-time): Lazy expansion (invocation-time): #define A 87 #define B A #undef A #define A 42 B => ??? #define A 87 #define B A #undef A #define A 42 B => ??? B => 87 B => A => 42 CPP
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May 14, 2002 Macro Languages AoPL, S'02 Order of Expansion Consider: #define id(X) X #define one(X) id(X) #define two a,b one(two) => ??? #define id(X) X #define one(X) id(X) #define two a,b one(two) => ???
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May 14, 2002 Macro Languages AoPL, S'02 Order of Expansion Consider: Inner (aka. “AOR”, call-by-value): #define id(X) X #define one(X) id(X) #define two a,b one(two) => ??? #define id(X) X #define one(X) id(X) #define two a,b one(two) => ??? one(two) => one(a,b) => *** arity error ‘one’
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May 14, 2002 Macro Languages AoPL, S'02 Order of Expansion Consider: Inner (aka. “AOR”, call-by-value): Outer (aka. “NOR”, call-by-name): #define id(X) X #define one(X) id(X) #define two a,b one(two) => ??? #define id(X) X #define one(X) id(X) #define two a,b one(two) => ??? one(two) => one(a,b) => *** arity error ‘one’ one(two) => id(two) => two => a,b
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Order of Expansion “Argument prescan”: one(two) #define id(X) X #define one(X) id(X) #define two a,b #define id(X) X #define one(X) id(X) #define two a,b CPP
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Order of Expansion “Argument prescan”: one(two) => id(a,b) #define id(X) X #define one(X) id(X) #define two a,b #define id(X) X #define one(X) id(X) #define two a,b CPP
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Order of Expansion “Argument prescan”: one(two) => id(a,b) => *** arity error ‘id’ #define id(X) X #define one(X) id(X) #define two a,b #define id(X) X #define one(X) id(X) #define two a,b CPP
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Order of Expansion “Argument prescan”: For piecing together new macro invocations partly from the arguments, partly from the body: one(two) => id(a,b) => *** arity error ‘id’ #define succ(X) ((X) + 1) #define call7(X) X(7) call7(succ) => succ(7) => ((7) + 1) #define succ(X) ((X) + 1) #define call7(X) X(7) call7(succ) => succ(7) => ((7) + 1) #define id(X) X #define one(X) id(X) #define two a,b #define id(X) X #define one(X) id(X) #define two a,b CPP
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May 14, 2002 Macro Languages AoPL, S'02 Recursion Consider: #define x 1+x x => ??? #define x 1+x x => ???
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May 14, 2002 Macro Languages AoPL, S'02 Recursion Consider: Definition-time (static intercept-and-reject): #define x 1+x x => ??? #define x 1+x x => ??? #define x 1*x *** definition-time error!
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May 14, 2002 Macro Languages AoPL, S'02 Recursion Consider: Definition-time (static intercept-and-reject): Invocation-time (non-termination): #define x 1+x x => ??? #define x 1+x x => ??? #define x 1*x *** definition-time error! x => 1+x => 1+1+x => … // loop at compile-time!
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Recursion “Dynamic intercept-and-ignore”: Keep stack of macro invocations Ignore invocations of already invoked macros: x => 1+x int x = 2; #define x 1+x x => ??? int x = 2; #define x 1+x x => ??? CPP
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May 14, 2002 Macro Languages AoPL, S'02 CPP: Recursion “Dynamic intercept-and-ignore”: Keep stack of macro invocations Ignore invocations of already invoked macros: x => 1+x // intercept-and-ignore: (at runtime x 3) int x = 2; #define x 1+x x => ??? int x = 2; #define x 1+x x => ??? CPP
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May 14, 2002 Macro Languages AoPL, S'02 M4 M4 (Unix Macro Preprocessor): Originally called “ratfor”: –“The Rational Fortran Preprocessor” Not tailored for a particular language universal preprocessor 30+ built-in constructions: macro definition, arithmetic evaluation, string operations, file and system interfacing, …
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May 14, 2002 Macro Languages AoPL, S'02 M4 Example Implicit arguments (named: $1, …, $9) Excess arguments ignored Missing arguments default to “” Quoting: –Expansion removes one layer of quotes Controls expansion-time (eager by default): define(‘square’, ‘ eval($1 * $1) ’ )
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May 14, 2002 Macro Languages AoPL, S'02 M4 Example Implicit arguments (named: $1, …, $9) Excess arguments ignored Missing arguments default to “” Quoting: –Expansion removes one layer of quotes Controls expansion-time (eager by default): define(‘square’, ‘ eval($1 * $1) ’ ) square(3) define(‘square’, ‘ eval($1 * $1) ’ ) square(3)
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May 14, 2002 Macro Languages AoPL, S'02 M4 Example Implicit arguments (named: $1, …, $9) Excess arguments ignored Missing arguments default to “” Quoting: –Expansion removes one layer of quotes Controls expansion-time (eager by default): define(‘square’, ‘ eval($1 * $1) ’ ) square(3) => eval(3 * 3) define(‘square’, ‘ eval($1 * $1) ’ ) square(3) => eval(3 * 3)
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May 14, 2002 Macro Languages AoPL, S'02 M4 Example Implicit arguments (named: $1, …, $9) Excess arguments ignored Missing arguments default to “” Quoting: –Expansion removes one layer of quotes Controls expansion-time (eager by default): define(‘square’, ‘ eval($1 * $1) ’ ) square(3) => eval(3 * 3) => 9 define(‘square’, ‘ eval($1 * $1) ’ ) square(3) => eval(3 * 3) => 9
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body }
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body }](http://images.slideplayer.com./16/5168193/slides/slide_56.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body }")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1]
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1]](http://images.slideplayer.com./16/5168193/slides/slide_57.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1]")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$](http://images.slideplayer.com./16/5168193/slides/slide_58.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )](http://images.slideplayer.com./16/5168193/slides/slide_59.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )](http://images.slideplayer.com./16/5168193/slides/slide_60.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 )")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))](http://images.slideplayer.com./16/5168193/slides/slide_61.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))")
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May 14, 2002 Macro Languages AoPL, S'02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: Recursion permitted: TC compile-time language to “break the recursion” \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))
![May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: Recursion permitted: TC compile-time language to break the recursion \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))](http://images.slideplayer.com./16/5168193/slides/slide_62.jpg "May 14, 2002 Macro Languages AoPL, S 02 TEXTEX Flexible invocation syntax: Designed by macro programmer Parsing ambiguities (chooses shortest invocation) –Implies: Recursion permitted: TC compile-time language to break the recursion \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ \def \vector #1[#2..#3]{ // header $({#1}_{#2},\ldots,{#1}_{#3})$ // body } \vector x’[0..n-1] => $({x’}_{0},\ldots,{x’}_{n-1})$ (x’ 0, …, x’ n-1 ) M M x // invokes M(M), not M(M(x))")
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May 14, 2002 Macro Languages AoPL, S'02 Syntax Macros C++ templates, Scheme, JTS, MS 2
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May 14, 2002 Macro Languages AoPL, S'02 C++ Templates Intended as a genericity mechanism But often used as a macro language
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May 14, 2002 Macro Languages AoPL, S'02 C++ Templates Intended as a genericity mechanism But often used as a macro language Syntax types: Arguments: id, const, all types (e.g. int ) The result is always a declaration
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May 14, 2002 Macro Languages AoPL, S'02 C++ Templates Intended as a genericity mechanism But often used as a macro language Syntax types: Arguments: id, const, all types (e.g. int ) The result is always a declaration Multiple definitions: template struct M { … }
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May 14, 2002 Macro Languages AoPL, S'02 C++ Templates Intended as a genericity mechanism But often used as a macro language Syntax types: Arguments: id, const, all types (e.g. int ) The result is always a declaration Multiple definitions: Constant folding: template struct M { … } (1 + 2) 3 // at compile-time
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May 14, 2002 Macro Languages AoPL, S'02 However… template struct ct_pow { static const int res = 1; }; template struct ct_pow { static const int res = X * ct_pow ::res; }; const int z = ct_pow ::res; // c-time z 125 template struct ct_pow { static const int res = 1; }; template struct ct_pow { static const int res = X * ct_pow ::res; }; const int z = ct_pow ::res; // c-time z 125
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May 14, 2002 Macro Languages AoPL, S'02 However… Constant folding + multiple definition = Turing complete (at compile-time)! template struct ct_pow { static const int res = 1; }; template struct ct_pow { static const int res = X * ct_pow ::res; }; const int z = ct_pow ::res; // c-time z 125 template struct ct_pow { static const int res = 1; }; template struct ct_pow { static const int res = X * ct_pow ::res; }; const int z = ct_pow ::res; // c-time z 125
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May 14, 2002 Macro Languages AoPL, S'02 Scheme Convenient pattern matching (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :)
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May 14, 2002 Macro Languages AoPL, S'02 Scheme Convenient pattern matching (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...)
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May 14, 2002 Macro Languages AoPL, S'02 Scheme Convenient pattern matching Multiple definitions: –Selection: first match in order listed (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...)
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May 14, 2002 Macro Languages AoPL, S'02 Scheme Convenient pattern matching Multiple definitions: –Selection: first match in order listed Ellipsis list constructor: “ … ” –More on this later… (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b …) (if b (and …) #f)))))))))))))))))) :) (and a (if x y z) c) => (if...)
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i))))
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) => ((lambda (x) (+ x x)) 5) )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) => ((lambda (x) (+ x x)) 5) => 10 )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion With -conversion: (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) => ((lambda (x) (+ x x)) 5) => 10 ((gen-inc x) 5) )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion With -conversion: (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) => ((lambda (x) (+ x x)) 5) => 10 ((gen-inc x) 5) => ((lambda (x’) (+ x’ x)) 5) )
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May 14, 2002 Macro Languages AoPL, S'02 Hygienic Macro Expansion Scheme has automatic -conversion: Identifier renaming to avoid name capture let ((x 3)) ( Without -conversion With -conversion: (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) (define-syntax gen-inc (syntax-rules () ((gen-inc i) (lambda (x) (+ x i)))) ((gen-inc x) 5) => ((lambda (x) (+ x x)) 5) => 10 ((gen-inc x) 5) => ((lambda (x’) (+ x’ x)) 5) => 8 )
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May 14, 2002 Macro Languages AoPL, S'02 Compile-Time Programming Basically compile-time functions on S-exps Lazy (inv.-time) body expansion ( evaluation): (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if
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May 14, 2002 Macro Languages AoPL, S'02 Compile-Time Programming Basically compile-time functions on S-exps Lazy (inv.-time) body expansion ( evaluation): Non-termination possible: (define-syntax ct-loop (syntax-rules () ((ct-loop) (ct-loop)))) (define-syntax ct-loop (syntax-rules () ((ct-loop) (ct-loop)))) (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if
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May 14, 2002 Macro Languages AoPL, S'02 Compile-Time Programming Basically compile-time functions on S-exps Lazy (inv.-time) body expansion ( evaluation): Non-termination possible: (define-syntax ct-loop (syntax-rules () ((ct-loop) (ct-loop)))) (ct-loop) => // c-time loop (define-syntax ct-loop (syntax-rules () ((ct-loop) (ct-loop)))) (ct-loop) => // c-time loop (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if (define-syntax m (syntax-rules () ((m) (if 1 2 3 4)))) (m) => // *** parse error: too many arg’s to if
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May 14, 2002 Macro Languages AoPL, S'02 JTS JTS (“Jakarta Tool Suite”): macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm
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May 14, 2002 Macro Languages AoPL, S'02 JTS JTS (“Jakarta Tool Suite”): Argument types: name, exp, stm, decl, class, type Result types: “ exp ”, “ stm ”, “ mth ”, “ cls ”, “ prg ” macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm
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May 14, 2002 Macro Languages AoPL, S'02 JTS JTS (“Jakarta Tool Suite”): Argument types: name, exp, stm, decl, class, type Result types: “ exp ”, “ stm ”, “ mth ”, “ cls ”, “ prg ” –Fixed invocation syntax: macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm #swap(C.x, y);
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May 14, 2002 Macro Languages AoPL, S'02 JTS JTS (“Jakarta Tool Suite”): Argument types: name, exp, stm, decl, class, type Result types: “ exp ”, “ stm ”, “ mth ”, “ cls ”, “ prg ” –Fixed invocation syntax: –Safe: Guaranteed termination, only generate legal syntax macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm macro swap(AST_QualifiedName x, AST_QualifiedName y) local temp // explicit -conversion stm{ // body constructor: stm integer temp = x; x = y; y = temp; }stm #swap(C.x, y);
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May 14, 2002 Macro Languages AoPL, S'02 MS 2 MS 2 (“Meta Syntactic Macro System”): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); } syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); }
![May 14, 2002 Macro Languages AoPL, S 02 MS 2 MS 2 ( Meta Syntactic Macro System ): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); }](http://images.slideplayer.com./16/5168193/slides/slide_89.jpg "May 14, 2002 Macro Languages AoPL, S 02 MS 2 MS 2 ( Meta Syntactic Macro System ): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); }")
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May 14, 2002 Macro Languages AoPL, S'02 MS 2 MS 2 (“Meta Syntactic Macro System”): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple); syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple);
![May 14, 2002 Macro Languages AoPL, S 02 MS 2 MS 2 ( Meta Syntactic Macro System ): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple); syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple);](http://images.slideplayer.com./16/5168193/slides/slide_90.jpg "May 14, 2002 Macro Languages AoPL, S 02 MS 2 MS 2 ( Meta Syntactic Macro System ): Turing complete AST programming language –for computing C parse trees at compile-time syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple); syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc( print_ ,name))(arg) { switch (arg) id; `{ case $id: printf( %s , $(pstring(id)));}), ids))})); } myenum fruit { apple, orange }; print_fruit(apple);")
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May 14, 2002 Macro Languages AoPL, S'02 8 Languages: { CPP, M4, T E X, Dylan, C++ Templates, Scheme, JTS, MS 2 } Macro Survey
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May 14, 2002 Macro Languages AoPL, S'02 8 Languages: { CPP, M4, T E X, Dylan, C++ Templates, Scheme, JTS, MS 2 } 31 Properties: { Level of operation, body expansion, order of expansion, … } Macro Survey
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May 14, 2002 Macro Languages AoPL, S'02 8 Languages: { CPP, M4, T E X, Dylan, C++ Templates, Scheme, JTS, MS 2 } 31 Properties: { Level of operation, body expansion, order of expansion, … } Macro Survey
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May 14, 2002 Macro Languages AoPL, S'02 Declarative: Based entirely on simple concepts: grammars and substitution Safe: Guaranteed termination Only generate legal (and -converted) syntax Flexible: All (55) nonterminals may be arg and return types Invocation syntax design (guides parsing)
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May 14, 2002 Macro Languages AoPL, S'02 On all (55) Nonterminals : macro pi ::= { 3.1415926 }
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May 14, 2002 Macro Languages AoPL, S'02 On all (55) Nonterminals : macro pi ::= { 3.1415926 } macro maybe ::= { if (random(2)==0) } macro maybe ::= { if (random(2)==0) }
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May 14, 2002 Macro Languages AoPL, S'02 On all (55) Nonterminals : macro pi ::= { 3.1415926 } macro maybe ::= { if (random(2)==0) } macro maybe ::= { if (random(2)==0) } macro plus ( ) ::= { concat(star( ), ) } macro plus ( ) ::= { concat(star( ), ) }
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May 14, 2002 Macro Languages AoPL, S'02 Example: repeat Invocation syntax design: Guides the parser macro repeat until ( ) ; ::= { { while ( ) } macro repeat until ( ) ; ::= { { while ( ) }
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May 14, 2002 Macro Languages AoPL, S'02 Example: repeat Invocation syntax design: Guides the parser Code duplication: Worst-case: O(2 n ) macro repeat until ( ) ; ::= { { while ( ) } macro repeat until ( ) ; ::= { { while ( ) }
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May 14, 2002 Macro Languages AoPL, S'02 Example: repeat macro repeat until ( ) ; ::= { { bool first = true; while (first || ! ) { first = false; } macro repeat until ( ) ; ::= { { bool first = true; while (first || ! ) { first = false; }
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May 14, 2002 Macro Languages AoPL, S'02 Example: repeat -Conversion: first => first_87 macro repeat until ( ) ; ::= { { bool first = true; while (first || ! ) { first = false; } macro repeat until ( ) ; ::= { { bool first = true; while (first || ! ) { first = false; }
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions Macros with same name: si/si-sinon : Parsing: Which macro to select? macro si ( ) ::= { if ( ) } macro si ( ) sinon ::= { if ( ) else } macro si ( ) ::= { if ( ) } macro si ( ) sinon ::= { if ( ) else }
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May 14, 2002 Macro Languages AoPL, S'02 Specificity Parsing macro select from where macro select all from where macro select from where macro select all from where
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May 14, 2002 Macro Languages AoPL, S'02 Specificity Parsing Challenge rounds: –Select most specific productions (wrt. FIRST sets) Resolves many ambiguities Independent of definition-order Overloading Avoids keywordification Commit no branch explosion, no backtracking macro select from where macro select all from where macro select from where macro select all from where
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May 14, 2002 Macro Languages AoPL, S'02 Pretty Print and Error Reporting Pretty Printing: Terminal printers: ASCII, L A E X, HTML ( +/- expansion) T
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May 14, 2002 Macro Languages AoPL, S'02 Pretty Print and Error Reporting Pretty Printing: Terminal printers: ASCII, L A E X, HTML ( +/- expansion) Error Reporting: stdout, HTML *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] T
![May 14, 2002 Macro Languages AoPL, S 02 Pretty Print and Error Reporting Pretty Printing: Terminal printers: ASCII, L A E X, HTML ( +/- expansion) Error Reporting: stdout, HTML *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] T](http://images.slideplayer.com./16/5168193/slides/slide_106.jpg "May 14, 2002 Macro Languages AoPL, S 02 Pretty Print and Error Reporting Pretty Printing: Terminal printers: ASCII, L A E X, HTML ( +/- expansion) Error Reporting: stdout, HTML *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] *** symbol errors: *** test.wig:7: Identifier ‘inf’ not declared in macro argument ‘S’ in macro invocation ‘reader’ (test.wig:7) defined in [std.wigmac:44] T")
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May 14, 2002 Macro Languages AoPL, S'02 Concurrency Stack
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May 14, 2002 Macro Languages AoPL, S'02 Representation macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D
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May 14, 2002 Macro Languages AoPL, S'02 Representation macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D
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May 14, 2002 Macro Languages AoPL, S'02 Representation macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D macro M XY ( ) ::= { X,, Y } A, M XY (B, C), D A, X, B, C, Y, D “Weaving” yields transparency! weave
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May 14, 2002 Macro Languages AoPL, S'02 Metamorphic Syntax Macros
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May 14, 2002 Macro Languages AoPL, S'02 Argument Structure Many variants of an abstraction? enum { zero }; enum { zero, one }; enum { zero, one, two }; … enum { zero }; enum { zero, one }; enum { zero, one, two }; …
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May 14, 2002 Macro Languages AoPL, S'02 Argument Structure Many variants of an abstraction? –Syntax: Argument structure? –Transformation: Specification? enum { zero }; enum { zero, one }; enum { zero, one, two }; … enum { zero }; enum { zero, one }; enum { zero, one, two }; …
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May 14, 2002 Macro Languages AoPL, S'02 Argument Structure Many variants of an abstraction? –Syntax: Argument structure? –Transformation: Specification? enum { zero }; enum { zero, one }; enum { zero, one, two }; … enum { zero }; enum { zero, one }; enum { zero, one, two }; … Safety?
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions macro enum { }; ::= { const int = 0; } macro enum {, }; ::= { const int = 0; const int = 1; } macro enum {,, }; ::= { const int = 0; const int = 1; const int = 2; } macro enum { }; ::= { const int = 0; } macro enum {, }; ::= { const int = 0; const int = 1; } macro enum {,, }; ::= { const int = 0; const int = 1; const int = 2; }
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…}
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions decls enum { id } ; enum { id, id } ; enum { id, id, id } ; decls enum { id } ; enum { id, id } ; enum { id, id, id } ; macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} Corresponds to grammar extension:
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions decls enum { id } ; enum { id, id } ; enum { id, id, id } ; decls enum { id } ; enum { id, id } ; enum { id, id, id } ; macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} Corresponds to grammar extension: Three unrelated productions
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions decls enum { id } ; enum { id, id } ; enum { id, id, id } ; decls enum { id } ; enum { id, id } ; enum { id, id, id } ; macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} Corresponds to grammar extension: Problems: Only fixed (finite) extent Three unrelated productions
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Definitions decls enum { id } ; enum { id, id } ; enum { id, id, id } ; decls enum { id } ; enum { id, id } ; enum { id, id, id } ; macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} macro enum { }; ::= {…} macro enum {, }; ::= {…} macro enum {,, }; ::= {…} Corresponds to grammar extension: Problems: Only fixed (finite) extent Highly redundant Three unrelated productions
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May 14, 2002 Macro Languages AoPL, S'02 Lists Scheme: Special list constructor: “... ” decls ( enum id * ) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b...) (if b (and...) #f)))) (define-syntax and (syntax-rules () ((and) #t) ((and b) b) ((and b...) (if b (and...) #f)))) (enum x y z)
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May 14, 2002 Macro Languages AoPL, S'02 e-BNF MS 2 : Regular expressions: –Optionals “ ? ”, lists “ +, * ”, tuples “ {…} ”, t -sep. lists “ \+t ” syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); syntax decl myenum[] {| $$id::name { $$+\,id::ids }; |} { return (list(`[enum $name $ids;], `[$(symbolconc(“print_”,name))(arg) { switch (arg) $(map((| @id id; `{ case $id: printf(“%s”, $(pstring(id)));}), ids))})); decls enum { id , } ; myenum fruit { apple, orange }; print_fruit(apple);
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May 14, 2002 Macro Languages AoPL, S'02 Grammar Dylan (and JSE, a Java adaptation): Describe argument syntax via user-defined nonterminals decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Grammar Dylan (and JSE, a Java adaptation): Describe argument syntax via user-defined nonterminals –Unsafe: Transformations return lexical token sequences Return user defined abstract syntax trees? decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Metamorphisms : Attach host nonterminals to user def’d nonterminals Specify morphing (into host syntax) inductively metamorph enums; macro … … ::= { … … } morph … ::= { … } metamorph enums; macro … … ::= { … … } morph … ::= { … } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum Ideally: enum { a, b, c }; const int a = 0; const int b = 1; const int c = 2; const int a = 0; const int b = 1; const int c = 2; =>
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum Ideally: But requires compile-time evaluation: 0, 1, 2, … enum { a, b, c }; const int a = 0; const int b = 1; const int c = 2; const int a = 0; const int b = 1; const int c = 2; =>
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum Ideally: But requires compile-time evaluation: 0, 1, 2, … Instead generate: enum { a, b, c }; const int a = 0; const int b = 1; const int c = 2; const int a = 0; const int b = 1; const int c = 2; => enum { a, b, c }; const int e = 0; const int a = e++; const int b = e++; const int c = e++; const int e = 0; const int a = e++; const int b = e++; const int c = e++; =>
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum metamorph enums; decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } morph , ::= { const int = e++; } metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } morph , ::= { const int = e++; } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } morph , ::= { const int = e++; } morph ::= { } metamorph enums; macro enum { } ; ::= { int e = 0; const int = e++; } morph , ::= { const int = e++; } morph ::= { } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –States: ( , ) – (T N)* sentential form – T* input string 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –States: ( , ) – (T N)* sentential form – T* input string –Transitions: –(t , t ) ( , ) –(N , ) ( , ), if N 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –Termination function: ( , ) = 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –Termination function: ( , ) = 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –Termination function: ( , ) = –|| t || = 0 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > …
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –Termination function: ( , ) = –|| t || = 0 –|| N 0 || = k+1 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … N 0 N 1 1 N 2 2 1 … N k k … 1 longest
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May 14, 2002 Macro Languages AoPL, S'02 Guaranteed Termination Termination proof: Transition system + termination function –Termination function: ( , ) = lexicographically ordered –|| t || = 0 –|| N 0 || = k+1 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … 0 1 2 … ( 0 ) > ( 1 ) > ( 2 ) > … N 0 N 1 1 N 2 2 1 … N k k … 1 longest
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May 14, 2002 Macro Languages AoPL, S'02 Metamorph Wellformedness Check at definition time: No left-recursion –guarantees parser termination: xlist xlist X xlist xlist X xlist X xlist xlist X xlist
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May 14, 2002 Macro Languages AoPL, S'02 Metamorph Wellformedness Check at definition time: No left-recursion –guarantees parser termination: Derivability –metamorphisms must derive something finite : xlist xlist X xlist xlist X xlist X xlist xlist X xlist xlist X xlist xlist X xlist xlist X xlist
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May 14, 2002 Macro Languages AoPL, S'02 Example: switch metamorph swb; metamorph swb; stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break; stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break;
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May 14, 2002 Macro Languages AoPL, S'02 Example: switch metamorph swb; macro switch ( ) { } ::= { { var x = ; } metamorph swb; macro switch ( ) { } ::= { { var x = ; } stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break; stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break;
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May 14, 2002 Macro Languages AoPL, S'02 Example: switch metamorph swb; macro switch ( ) { } ::= { { var x = ; } morph case : break; ::= { if (x == ) { } else } metamorph swb; macro switch ( ) { } ::= { { var x = ; } morph case : break; ::= { if (x == ) { } else } stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break; stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break;
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May 14, 2002 Macro Languages AoPL, S'02 Example: switch metamorph swb; macro switch ( ) { } ::= { { var x = ; } morph case : break; ::= { if (x == ) { } else } morph case : break; ::= { if (x == ) { } } metamorph swb; macro switch ( ) { } ::= { { var x = ; } morph case : break; ::= { if (x == ) { } else } morph case : break; ::= { if (x == ) { } } stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break; stm switch ( exp ) { swb } swb case exp : stms break; swb case exp : stms break;
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May 14, 2002 Macro Languages AoPL, S'02 Example: reserve => stm reserve ( res ) stm res id res stm reserve ( res ) stm res id res reserve ( a b c )...; acquire(a); acquire(b); acquire(c);...; release(c); release(b); release(a); acquire(a); acquire(b); acquire(c);...; release(c); release(b); release(a);
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May 14, 2002 Macro Languages AoPL, S'02 Example: reserve Requires non-local transformations e.g. “ b ” must generate both “ acquire(b) ” and “ release(b) ” at different locations => stm reserve ( res ) stm res id res stm reserve ( res ) stm res id res reserve ( a b c )...; acquire(a); acquire(b); acquire(c);...; release(c); release(b); release(a); acquire(a); acquire(b); acquire(c);...; release(c); release(b); release(a);
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May 14, 2002 Macro Languages AoPL, S'02 Multiple Results Extend metamorphisms: Attach host nonterminals to user def’d nonterminals metamorph res; macro … … ::= { … … … } morph … ::= { … } { … } metamorph res; macro … … ::= { … … … } morph … ::= { … } { … } stm reserve ( res ) stm res id res stm reserve ( res ) stm res id res
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May 14, 2002 Macro Languages AoPL, S'02 Example: reserve metamorph res; macro reserve ( ) ::= { { } } morph ::= { acquire( ); } { release( ); } morph ::= { } { } metamorph res; macro reserve ( ) ::= { { } } morph ::= { acquire( ); } { release( ); } morph ::= { } { } stm reserve ( res ) stm res id res stm reserve ( res ) stm res id res
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum (cont’d) enum { a, b, c }; const int e = 0; const int a = e++; const int b = e++; const int c = e++; const int e = 0; const int a = e++; const int b = e++; const int c = e++; =>
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May 14, 2002 Macro Languages AoPL, S'02 Example: enum (cont’d) Suppose no initialization expressions Instead generate: –CPS Style: Send initialization expression to metamorphism enum { a, b, c }; const int e = 0; const int a = e++; const int b = e++; const int c = e++; const int e = 0; const int a = e++; const int b = e++; const int c = e++; => enum { a, b, c }; const int a = 0; const int b = 1; const int c = 1+1; const int a = 0; const int b = 1; const int c = 1+1; =>
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May 14, 2002 Macro Languages AoPL, S'02 Metamorph Arguments metamorph enums( ); macro enum { ({1}) }; … { const int = 0; } morph , ({ +1}) ::= { const int = ; } morph ::= { } metamorph enums( ); macro enum { ({1}) }; … { const int = 0; } morph , ({ +1}) ::= { const int = ; } morph ::= { } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums
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May 14, 2002 Macro Languages AoPL, S'02 Metamorph Arguments metamorph enums( ); macro enum { ({1}) }; … { const int = 0; } morph , ({ +1}) ::= { const int = ; } morph ::= { } metamorph enums( ); macro enum { ({1}) }; … { const int = 0; } morph , ({ +1}) ::= { const int = ; } morph ::= { } decls enum { id enums } ; enums , id enums decls enum { id enums } ; enums , id enums enum {…x…}; => … const int x = 1+1+1+1; …
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May 14, 2002 Macro Languages AoPL, S'02 Metamorph Advantages Flexibility: Tree structures Non-local transformations (multiple results) Safety: No parse errors as a conseq. of macro expansion Guaranteed termination Simplicity: Based entirely on declarative concepts: grammars and substitution
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May 14, 2002 Macro Languages AoPL, S'02 vDSL: very Domain-Specific Language studies course Math101 title “Mathematics 101” 2 point fall term … exclusions Math101 <> MathA Math102 <> MathB prerequisites Math101, Math102 < Math201, Math202, Math203 Math101, CS101 < CS202 studies course Math101 title “Mathematics 101” 2 point fall term … exclusions Math101 <> MathA Math102 <> MathB prerequisites Math101, Math102 < Math201, Math202, Math203 Math101, CS101 < CS202
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May 14, 2002 Macro Languages AoPL, S'02 FIN
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May 14, 2002 Macro Languages AoPL, S'02 Next Week: metafront Macros are just a special case usage: A is an extension of B: m: L+ => L Make sure only need to write delta: = L+ \ L metafront x: A => B AB program.a program.b transformation input language input program(s)output program(s) output language
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