but sometimes unexpected when you don't know! :)
Hi,
I was playing around with using library functions to clarify my next
question, when I encounted the optimizing features of felix. I had
actually encountered it before when I was comparing performance between
felix and ocaml when I thought the console output might be skewing the
results because the ocaml version seemed to be buffering, so I removed
the display of the results of the tests, and suddenly felix was
infinitely more efficient than ocaml because it saw running the function
was useless, as the result wasn't being used. Pretty cool!
Anyway, how do you use an external function that has side-effects, and
still get the result? I had inferred a guess about generators from
comments (the manual doesn't seem to have caught up to them yet) using
"gen jseek ..." but that gives the same results.
I'm using svn from a few days ago (the current head build crashes).
//------------
#import <flx.flxh>
open Long;
type file = "FILE *";
fun jopen: string -> file = 'std::fopen($1.data(), "rw")';
fun jvalid : file -> bool = '$1!=(FILE*)0';
fun jseek: file * long * int -> int = 'std::fseek($1, $2, $3)';
proc jclose: file = '(void)std::fclose($1);';
fun jtell: file -> long = 'std::ftell($1)';
var fil = jopen ("t.txt");
if jvalid fil do
print "jopen returned 0\n";
else
print "jopen returned ... something\n";
done;
val x = jseek(fil, 0L, 2);
// uncommenting out the following to stop previous being elided
//print "jseek returned ";
//print x;
//endl;
val p = jtell(fil);
print "file size is ";
print p;
endl;
jclose(fil);
//------------
-------------------------------------------------------------------------
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