[Swift-devel] Re: folding/sequential-while/whatever and accessing data in files

[Mihael Hategan]

Why not

fold k, v in a until(@extractint(a[k]) <=2)) {
  a[k + 1] = countstep(a[k]);
}?

Would be closer to foreach, and it would not have the implicit variable
"foo".

On Fri, 2007-09-07 at 20:48 +0000, Ben Clifford wrote:
> So I fiddled a little and have this code that works ok:
> 
> iterate {
>   a[foo+1] = countstep(a[foo]);
>  print("extract int value ", at extractint(a[foo+1]));
> } until (@extractint(a[foo+1]) <= 2);
> 
> (fully program at the end of this message)
> 
> which runs countstep in sequence until a convergence criteria is met.
> 
> countstep is simple app which counts the number of bytes in its input file 
> and outputs that count to its output file (thus converges rapidly to 1)
> 
> What is different about this over previous repeat/while statements is 
> that:
>  
>  there's an implicitly defined variable 'foo' that iterate{} makes 
> available for each iteration. In the first iteration, the value of foo is 
> 0, and the value is increased with each subsequent iteration, up to 
> (Swift's version of) infinity.
> 
>  there's a function to move from file-content-space to 
> swift-expression-space (the previously discussed @extractint)
> 
> This seems to be the right direction to be going for 
> fold-like/iteration-like structures.
> 
> Full files follow:
> 
> $ cat fold2.swift:
> 
> type counterfile {}
> 
> (counterfile t) greeting(string m) { 
>   app {
>     echo m stdout=@filename(t);
>   }
> }
> 
> (counterfile t) countstep(counterfile i) {
>   app {
>     wcl @filename(i) @filename(t);
>   }
> }
> 
> counterfile startfile <"longstartint.txt">;
> 
> counterfile a[]  <fixed_array_mapper;files="a b c d e f g h i j k l m n o 
> p q r 
> s t u v w x y z">;
> 
> a[0] = greeting("793578934574893");
> 
> iterate {
>   a[foo+1] = countstep(a[foo]);
>  print("extract int value ", at extractint(a[foo+1]));
> } until (@extractint(a[foo+1]) <= 2);
> 
> 
> $ cat wcl
> #!/bin/bash
> 
> echo $(wc -c < $1) > $2
> 
> _______________________________________________
> Swift-devel mailing list
> Swift-devel at ci.uchicago.edu
> http://mail.ci.uchicago.edu/mailman/listinfo/swift-devel
>