Re: uncaught exception: error(existence_error(procedure,even/1),top_level/0)

James Gale wrote:
> 
> Hi I'm a newbee to prolog, and have just installed gnu prolog but what
> every I enter into the console I get this error, uncaught exception:
> error(existence_error(procedure,even/1),top_level/0)
> 
> example.
> 
> GNU Prolog 1.3.1
> By Daniel Diaz
> Copyright (C) 1999-2009 Daniel Diaz
> | ?- even(X).
> uncaught exception: error(existence_error(procedure,even/1),top_level/0)
> 
> not sure if the installation was wrong, but got not errors or I'm missing
> something very simple.
> also is there a good FAQ's page for this interpreter.
> 
> many thanks
> 
> James.
> 
> ps. sorry if this is a silly posting but didn't know what else to try :S 
> 
> 

I had the same error, but I figured it out :) What you have to do is create
a "logic database". This is a simple text file with the facts and the rules
of the program (or the "program's universe" if u like :P) Make a blank text
file and enter:

even(a).
even(b).

compile with:

petko@ubuntu:~/prog/prolog$ gplc nubble.pro 

execute with:

petko@ubuntu:~/prog/prolog$ ./nubble 

This is what you get:

GNU Prolog 1.3.0
By Daniel Diaz
Copyright (C) 1999-2007 Daniel Diaz
| ?- even(X).

X = a ? ;

X = b

yes
| ?- even(a).

yes
| ?- even(c).

no
| ?- 

I hope this helps :)

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