*****************************************************************************
 *                                                                           *
 *           ILLUSTRATION OF PROGRAM MANIPULATION USING TEYJUS               *
 *                                                                           *
 *  The script that follows shows the execution of the code that implements  *
 *  an interpreter for a simple functional programming language. There are   *
 *  annotations in the script that draw attention to particular aspects.     *
 *  These annotations are in the form of Lambda Prolog style comments.       *
 *                                                                           *
 *****************************************************************************


/* The module tested is eval_examples.mod. It is assumed to have been 
compiled at the outset. */

(gopalan@Diligence 32)% tjsim -p examples/handbook/progs/ eval_examples
Welcome to Teyjus

Copyright (C) 1999 Gopalan Nadathur
Teyjus comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions.  Please view the accompanying file
"COPYING" for more information.

/* The next three queries illustrate call by value evaluation for untyped 
lambda terms */

[eval_examples] ?- eval (app (abs f\ (abs x\ (abs y\ (app (app f x) y)))) (abs u\ (abs v\ u))) R.

The answer substitution:
R = abs (x\ abs (y\ app (app (abs (u\ abs (v\ u))) x) y))

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- eval (app (abs f\ (app (app f (abs x\ x)) (abs x\ (abs y\ y)))) (abs u\ (abs v\ u))) R.

The answer substitution:
R = abs (x\ x)

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- eval (app (abs f\ (app (app f (abs x\ x)) (abs x\ (abs y\ y)))) (abs u\ (abs v\ v))) R.

The answer substitution:
R = abs (x\ abs (y\ y))

More solutions (y/n)? y

no (more) solutions

/* The next set of queries provide simple illustrations of the evaluation
rules for some of the programming language primitives */

[eval_examples] ?- eval (eq (c 5) (c 0)) R.

The answer substitution:
R = false

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- eval (eq (c 5) (c 5)) R.

The answer substitution:
R = truth

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- eval (lss (c 5) (c 3)) R.

The answer substitution:
R = false

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- eval (lss (c 3) (c 5)) R.

The answer substitution:
R = truth

More solutions (y/n)? y

no (more) solutions

/* The remaining queries illustrate the evaluation of programs constructed
using the vocabulary of the functional programming language */

[eval_examples] ?- test 1 F.

The answer substitution:
F = c 120

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- test 2 F.

The answer substitution:
F = c 1

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- test 3 F.

The answer substitution:
F = c 5

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- test 4 F.

The answer substitution:
F = c 3

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- test 5 F.

The answer substitution:
F = cons (c 1) (cons (c 2) (cons (c 3) (cons (c 4) null)))

More solutions (y/n)? y

no (more) solutions

[eval_examples] ?- halt.
(gopalan@Diligence 33)%