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

Run-time Environments

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

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

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

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

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

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?

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]

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

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

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?

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]); }

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

Language Interoperability C# and Cobol bark at each other

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#)");

Cobol BigDog 000010 CLASS-ID. BigDog INHERITS Dog. 000020 ENVIRONMENT DIVISION. 000040 CONFIGURATION SECTION. 000050 REPOSITORY. 000060 CLASS Dog. 000070 OBJECT. 000080 PROCEDURE DIVISION. 000090 METHOD-ID. Bark OVERRIDE. 000160 PROCEDURE DIVISION. DISPLAY "WOOF WOOF (COBOL)". 000210 END METHOD Bark. 000220 END OBJECT. 000230 END CLASS BigDog.

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