1. Giuseppe Attardi Dipartimento di Informatica Università di Pisa
Advanced Programming
Giuseppe Attardi
Dipartimento di Informatica
Università di Pisa

2. Run-time Environments

3. Run-Time Environments
Java Virtual Machine
.NET Common Language Runtime
Provide a virtual execution environment
Exposes a structure organized into elements
Not a simple abstraction of physical resources

4. Controlling execution
Avoid damages
Install/uninstall is a nightmare
Component software?

5. Benefits Programmers Tool Developers Administrators and Users
Use of library and tools
Shorter integration time
Higher productivity
Tool Developers
Avoid the need to care about infrastructure and interoperability
Administrators and Users
Benefit from packages solutions
Independence from processors or OS

6. Common Language Infrastructure
Exposes all items in a unified type system
Packages elements in self-describing units
Loads and resolves interdependencies at runtime
Exposes information that allows verifying the type-safety
Execution Engine enforces politics
Metadata available at runtime enables dynamic and extensible solutions

7. Question
Is it feasible to build a runtime common to all programming languages?

8. More in detail Prolog PHP 3 LISP How to implement logic variable?
Can one use the Warren-Abstract-Machine?
PHP 3
Why assignment has unusual behavior?
LISP
How to handle multiple-values?

9. Prolog example append(X, Y, Z) :- append(NIL, Y, Y) :-
append([A . X], Y, [A . Z] ) :- append(X, Y, Z).
:- append([a . b . c], [d . e], R)
R = [a . b . c . d . e]

10. Prolog backtrack :- append(X, Y, [a . b]) :- append(X, NIL, [a . b])
X = [a]
Y = [b]
X = [a . b]
Y = NIL

11. PHP Assignement $str = ‘Ciao.’; $str2 = $str;
$str{strlen($str) – 1} = ‘!’;
echo $str2;
$var = $othervar
Performs copy of the value of $othervar
$var = &$othervar
Assignment by reference

12. Control Can we implement tail-recursion in C?
How to handle synchronization?
Function pointers?
How to invoke an arbitrary function given a list of arguments?

13. General Function Invoker
invoke(fun, argn, arglist) {
if (n==0)
return f();
else if (n==1)
return f(arg[0]);
else
return fun(arg[0], arg[1], .. , arg[n-1]); }

14. Basic Data Types Strings in C, Pascal and C++ are different
Array in row or column order?

15. Language Interoperability
C# and Cobol bark at each other

16. C# dog using System; public class Dog {
public virtual void RollOver () { Console.WriteLine("Scratch my tummy."); Bark(); }
public virtual void Bark () { Console.WriteLine("WOOF WOOF (C#)");

17. Cobol BigDog 000010 CLASS-ID. BigDog INHERITS Dog.
ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
REPOSITORY.
CLASS Dog.
OBJECT.
PROCEDURE DIVISION.
METHOD-ID. Bark OVERRIDE.
PROCEDURE DIVISION.
DISPLAY "WOOF WOOF (COBOL)".
END METHOD Bark.
END OBJECT.
END CLASS BigDog.

18. Barfing dogs
public class Demo { public static void Main() { Dog d = new Dog(); BigDog b = new BigDog(); d.RollOver(); b.RollOver(); } }