still trying to make closures work

[Sean McIlroy]

HEY TIM

CLOSURES ARE APPARENTLY A STUBBORN PROBLEM. I'VE TRIED A COUPLE THINGS
(THE FUNCTION-BASED APPROACH YOU SUGGESTED AND ALSO AN OBJECT-BASED
APPROACH) WITHOUT SUCCESS. PROBABLY I HAVEN'T UNDERSTOOD WHAT YOU WERE
GETTING AT (SEE BELOW FOR MY TAKE ON IT). COULD YOU TAKE A LOOK AT THE
CODE BELOW AND SEE IF I'M DOING SOMETHING OBVIOUSLY WRONG? I'M NOT
ATTACHED TO EITHER APPROACH; I'M JUST HOPING TO GET THIS TO WORK
SOMEHOW.

#) THIS STUFF WORKS:

function list(...) {return(argv(0,nargs()))}

function tail(list)
{
returnvalue = []
for (i=1; i<sizeof(list); i++) returnvalue[i-1]=list[i]
return(returnvalue)
}

function union(list1,list2)
{
accumulator = list1
offset = sizeof(list1)
for (index in list2) {accumulator[offset+index] = list2[index]}
return(accumulator)
}

function testpolynomial(a,b,c,d) {return(2*pow(a,3)+3*pow(b,2)+5*pow(c,
2)+4*pow(d,3))}

#) THIS STUFF DOESN'T WORK:

#) HERE IS MY UNDERSTANDING OF THE SOLUTION YOU SUGGESTED:
function evalclosure(closure,variablebindings) {return(closure[0]
(varg(union(tail(closure),variablebindings))))}

#) HERE IS MY ATTEMPT AT AN OBJECT-BASED SOLUTION:
class closure
{
method init(function,constantbindings) {$.function=function;
$.constantbindings=constantbindings}
method evaluated(variablebindings)
{return($.function(varg(union($.constantbindings,variablebindings))))}
}

functionsuccess = testpolynomial(1,2,3,4)==evalclosure(list(polynomial,
1,2),list(3,4))
objectsuccess =
testpolynomial(1,2,3,4)==closure(testpolynomial,list(1,2)).evaluated(list(3,4))

AS MENTIONED, functionsuccess==objectsuccess==0. BUMMER !!

peace
stm

[Tim Thompson]

> I'VE TRIED A COUPLE THINGS
> (THE FUNCTION-BASED APPROACH YOU SUGGESTED AND ALSO AN OBJECT-BASED
> APPROACH) WITHOUT SUCCESS.

A function-based approach (i.e. something that is closer to the example I
gave) will probably be easier to debug, if you're having trouble. Less
things to go wrong.

I don't have time right now to look at it in detail, but:

1) I notice you're using "function" as variable and element names - I'm
surprised that doesn't throw an error right away - you should use
non-reserved keywords for element names.

2) Break up complex statements into several statements, and add print
statements liberally to see what's going on.

...Tim...

[Sean McIlroy]

> To instanciate an object you must use the 'new' keyword:

AHA !! that's got it. thanks a bunch.

stm