Comments on: Factor: a stack-based programming language

By: simon

simon — Sun, 04 Feb 2007 07:29:35 +0000

>In the same family you should not forget Postscript!

C’est vrai ça (hey, why English? Don’t we all speak French here? And I’m sure those who don’t will be more than pleased to learn our language, as we did for theirs :-))… J’ai toujours trouvé le postscript fantastique.. Un peu lent, peut-être Mais vraiment intéressant.
Mais “factor” a l’air épatant. Merci !

P.S : j’espère que tout va bien !

By: anonymous

anonymous — Fri, 19 Jan 2007 16:07:40 +0000

Now, that’s one nasty sig

By: Christian Cornelssen

Christian Cornelssen — Fri, 19 Jan 2007 13:04:09 +0000

perl -nle ‘print pack(”B*”,$_)’

does the same job, but yes, the factor code is elegant.

By: Samuel Tardieu

Samuel Tardieu — Thu, 18 Jan 2007 21:15:23 +0000

Daniel: I was not comfortable in introducing yet another concept here (make), while I assumed everyone familiar with functional languages would recognize reduce. But thanks for your input, it looks just like my own implementation indeed.

And by the way I read your post earlier today already

By: Daniel Ehrenberg

Daniel Ehrenberg — Thu, 18 Jan 2007 17:23:19 +0000

This is a great example. There's just a little thing about your ascii encoding that could be improved. "" [ 2 >base 8 CHAR: 0 pad-left append ] reduce is O(n^2), because it appends to "" n times. This might be OK for a short string, but for longer strings, it could take a really long time. A more efficient way to do it is using make. I happen to have just written a summary of how to use make here. The (untested) way to rewrite your code using make is: [ [ 2 >base 8 CHAR: 0 pad-left % ] each ] "" make. The way that is implemented, it takes a vector and repeatedly appends on to it in place before converting the result to a string. This way, you don't have to copy the string so many times.

By: Samuel Tardieu

Samuel Tardieu — Thu, 18 Jan 2007 07:51:01 +0000

Thomas: here is a possible Factor quine.

[ pprint " dup call" print ] dup call

By: Samuel Tardieu

Samuel Tardieu — Thu, 18 Jan 2007 07:45:54 +0000

Thomas: yeah, I like quines too.

By: Thomas

Thomas — Wed, 17 Jan 2007 23:57:53 +0000

In the same family you should not forget Postscript!

Here’s an example I like of a Postscript program that renders its own source text, using the stack to create a function and pass it as argument to itself for the purpose of displaying it…

%!PS-Adobe-2.0
{ ($Id: //depot/src/self.ps#5 $) pop
20 616 moveto /Helvetica-Bold findfont 12 scalefont setfont
(%!PS-Adobe-2.0) show
20 600 moveto
/tshow { currentpoint pop dup 550 ge { neg 20 add -16 rmoveto } { pop }
ifelse show }
bind def
4 dict dup /cdict exch def
dup 40 (\\$) put
dup 41 (\\$) put
92 (\\\\) put
/cshow { dup cdict exch known { dup cdict exch get }
{ 1 string dup 0 4 3 roll put } ifelse show } bind def
/xshow {
dup type /arraytype eq { ({ ) tshow { xshow } forall (} ) tshow }
{ dup type /nametype eq { dup xcheck not { (/) tshow } if } if
dup type /stringtype eq { ($) tshow { cshow } forall ($ ) tshow }
{ 20 string cvs tshow ( ) tshow } ifelse } ifelse } def
xshow
{ dup exec showpage } { xshow } forall } dup exec showpage