ILP (Iterprete para un Lenguaje Pila),
thus ISL (Interpreter for a Stack Language)

* Build *

The source is commented in Spanish, but you can get interpreter messages
in english with:

$ make en

If you want to install it, just copy usr/ilp to /usr/local/bin.

If your compiler doesn't support the 'inline' directive, please comment the
HAS_INLINE define in the config.h file.

* Features *

 - Types:
 	integers	digits or - and digits (negative values)
 	variables	identifiers form a to z
 	addresses	program address (see :)
 	
 - Operators:
 	+	a b +	-> a + b
 	-	a b -	-> a - b
  	/	a b /	-> a / b
 	* 	a b *	-> a * b
 	=	a b =	-> a = b

 	E	a b E	-> a == b
 	<	a b <	-> a < b
 	>	a b >	-> a > b
 	~	a ~	-> NOT a 
 
 - Input/Output:
 	$	to screen the value in stack
 	$$	to screen the value in stack plus end of line
 	"	to screen literals until "
 		control characters: \n end of line
		                    \t tab
				    \" double quotes
				    \\ left slash
 	?	push a value from keyboard
 	
 - Loop:
 	:	push address
 	^	a b ^	-> jumps to a adress if b is not zero
 
 - Conditional:
 	!	a ! bloq -> pops a and execs bloq if a is not zero
 
 - Misc:
	#	comment until end of line
	;	points end of block (see conditional)
	.	a . -> ends the program returning the system a
		by default the programs return 0

* Known problems *

	- The line count means executed lines, so the loops make the line
	count confusing
	- Push/operator notation is weird :-)

* Examples *

Some comparisons with C:

/* in C */
for(i=0;i<10;i++)
	printf("iteration %i\n",i);

# in LP
i 0 =
:
	"iteration " i $$
	i i 1 + = # this is i=i+1
i 10 < ^

/* in C */
if(a==b)
	printf("a equal to b");
else
{
	if(a>b)
		printf("a bigger than b");
	else
		printf("a smaller than b");
}

# in LP (there's nothing like 'else')
a b E !
	"a equal to b" ;
a b > !
	"a bigger than b" ;
a b < !
	"a smaller than b" ;

A program:

"Multiplication table\nEnter a number: " a ? = j 1 = i 10 = : " " a $
"x" j $ "=" a j * $$ j j 1 + = i i 1 - = i ^ # A simple example

Another program:

: "The bomb game\n\nThere are 19 bombs and we must drop from 1 to 5 each"
" one each turn.\nThe player with the last bomb in his/her hand... boom!"
"\n\n" a 19 = : "There are " a $ " bombs, " : "how many do you wanna drop? "
b ? = b 5 > b 1 < + ! "you cannot drop more than 5 bombs neither less than "
"1\n" ; b 5 > b 1 < + ^ a a b - = c 6 b - = "there are " a $ " bombs, I "
"drop " c $$ a a c - = a 1 > ^ "there's 1 bomb and you have it in your "
"hand!\nYou're over... Play again (0 to end)? " b ? = b ^ # The bomb game

* Author *

	Juan J. Martinez <jjm@usebox.net>

***