Thank you Jon and Jakub.
yeah registered on the IRC, im just use to being on IRC that i dont need to
register so i never realized.
The dup was meant to be 3dup, but when i wrote it in i forgot about the 3,
on my source code its 3dup.
I've been working my way through the code in the listener, helps a lot to
understand the code.
2011/8/17 Jakub Ružička <ruzicka.ja...@gmail.com>
> 2011/8/16 Mute clown <withnom...@gmail.com>:
> > Never used a mailing list before, got kinda pushed into using it since
> for
> > some reason i cant talk in IRC.
>
> Maybe you need to register your nick?
>
>
> > I am trying to learn how to use factor, the whole stack oriented,
> > concatenative programming is alien to me. I am trying to implement Herons
> > Formula, to work out the area of a triangle:
> > Area = sqrt(s(s-a)(s-b)(s-c))
> > s = a+b+c /2
> > I've sort of worked out how to do s:
> > : dev2 ( d -- s ) 2 / ;
> > : sem ( a b c -- s ) + + dev2 ;
> > Problem 1:
> > IDK why the following doesn't work.
> > : sem ( a b c -- s ) dup + + dev2 ;
>
> why dup? that equals to `a b c c + + 2 /` so the stack effect is ( a b
> c -- a s ). Don't dup, let the word "eat" all the arguments. If you
> want to dup `a b c`, use 3dup.
>
>
> > Problem 2:
> > say i get the above problem fixed(use dup before calling the word)
> > I dont know how to proceed with the current stack:
> > -bottom of the stack-
> > a
> > b
> > c
> > s
> > -top of the stack-
> > i've tried various words to modify the top of the stack but, can't seem
> to
> > arrange it into a way so i can compute what i need.
>
> Either use tri@ (tri, tri* and tri@ do different things with 3
> quotations/values) or create array from a, b, c using 3array.
>
> Here are my attempts to solve your problem with same stack configuration:
>
> USING: arrays kernel math math.functions sequences ;
> IN: heron
>
> : s ( a b c -- s ) + + 2.0 / ;
> : area ( a b c -- S ) 3dup s dup
> [ [ swap - ] curry tri@ ] dip * * * sqrt ;
>
> ! using array
> : ss ( abcseq -- s ) sum 2.0 / ;
> : area2 ( a b c -- S ) 3array dup ss
> [ 0 suffix ] dip [ swap - ] curry map product sqrt ;
>
> If you don't understand, break into tiniest bits and run those
> interactively in listener. Also, look up unknown words at
> docs.factorcode.org and experiment with them to understand. Feel free
> to ask for clarification.
>
> Also, this one can be solved wihtou too much shuffling but some
> equations are really pain and in that case, consider using lexical
> variables, http://docs.factorcode.org/content/article-locals-examples.html
> has nice example with quadratic roots.
>
>
> Regards
> Jakub
>
>
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