[REBOL] Bug in 'use? Re:(3)

[lmecir]

The following has been written:

> > Hi Ladislav, 15-Jul-2000 you wrote:
> >
> > >you are right, the problem is caused by a context
> manipulation -
> > >Use unsets your Middle every time it gets executed. My
> suggestion
> > >is to not use Use in recursive functions, while this problem
> > >doesn't get corrected.
> >
> > Judging from the nature of recursiveness, that's a little
hard,
> isn't it? ;-)
> >
> > Do you know if this problem has already been reported to
> feedback?
> >
> > Kind regards,
> > --
> > Ole Friis <[EMAIL PROTECTED]>
> >

here is a pretty simple example showing the problem:

temporary: "global temporary"
recfun: func [level] [
use [temporary] [
if level < 1 [
temporary: "temporary"
recfun level + 1
print ["Temporary:" temporary]
]
]
]
recfun 0

; The result:
** Script Error: temporary has no value.
** Where: temporary

; let's define a function r-use like this:
r-use: func [
"Defines words local to a block."
words [block!] "Local word(s) to the block"
body [block!] "Block to evaluate"
] [
do function [] words body
]

; and now use R-use instead of native Use
temporary: "global temporary"
recfun: func [level] [
r-use [temporary] [
if level < 1 [
temporary: "temporary"
recfun level + 1
print ["Temporary:" temporary]
]
]
]
recfun 0

; The result:
Temporary: temporary

Ladislav

[REBOL] Bug in 'use? Re:(3)

[lmecir]

Hi,

> Hi Ladislav, 15-Jul-2000 you wrote:
>
> >you are right, the problem is caused by a context
manipulation -
> >Use unsets your Middle every time it gets executed. My
suggestion
> >is to not use Use in recursive functions, while this problem
> >doesn't get corrected.
>
> Judging from the nature of recursiveness, that's a little hard,
isn't it? ;-)
>
> Do you know if this problem has already been reported to
feedback?
>
> Kind regards,
> --
> Ole Friis <[EMAIL PROTECTED]>
>
> Amiga is a trademark of Amiga Inc.
>

You should probably report it to feedback. BTW, did you succeed to
sort the permutations correctly?

One more question for everybody. What do you want to see after
executing:

blk: copy []
probeblk: func [] [
prin mold blk
prin ": "
print mold reduce blk
]
recfun: func [x] [
append blk 'x
either x <= 1 [
probeblk
] [
recfun x - 1
]
]
recfun 3
probeblk

Regards
Ladislav

[REBOL] Bug in 'use? Re:(3)

[bhandley]

Ole,

> Thanks! In the meantime, I got it working by simply having the temporary
> variables as parameters to the function. Mean, but it works.

You don't need temporary variables. You can use local function variables.

Either via

func [x /local a-local][the-code]

or via

function [x][a-local][the-code]

Giving you back something that you lost with a broken 'use.

Brett.