[REBOL] Re: Tools for Rebol Coders
From: joel:neely:fedex at: 7-Jan-2002 7:21
Hi, Ladislav and Romano
Ladislav Mecir wrote:
> Hi Romano,
>
> <<Romano>>
>
> >> a: func[][make error! "p"]
> >> b: func[][return make error! "p"]
> >> error? a
> ** User Error: p
> ** Near: make error! "p"
> >> error? b
> == true
>
> >> a: func[][first [p:]]
> >> b: func[][return first [p:]]
> >> a
> == p:
> >> b
> == p
>
> (...)
> <</Romano>>
>
> The first sample:
>
> My POV is, that the first sample's function A should behave
> exactly like the first sample's function B...
>
> The second sample:
>
> ... I think, that this is a bug (discovered by you).
>
Based on the documented (RCUG) meaning of RETURN, I agree
with Ladislav that both examples demonstrate bugs in REBOL.
As you know from the Expressions Chapter, blocks return
their last value when they return from evaluation:
do [1 + 3 5 + 7]
12
This is also true for functions. The last value is returned
as the value of the function:
sum: func [a b] [
print a
print b
a + b
]
print sum 123 321
123
321
444
In addition, the return function can be used to stop the
evaluation of a function at any point and return a value...
The verbiage and examples lead me to conclude that the only
difference between explicitly RETURNing a value and implicitly
returning the last value is that RETURN may be used to exit
prematurely
at any point within the function. Nowhere that
I can find does the documentation state (nor imply) that
f: func [...]
[ ...
some-expression
]
should be any different in value nor effect from
f: func [...]
[ ...
return some-expression
]
(particle physics notwithstanding... ;-)
-jn-
--
; sub REBOL {}; sub head ($) {@_[0]}
REBOL []
# despam: func [e] [replace replace/all e ":" "." "#" "@"]
; sub despam {my ($e) = @_; $e =~ tr/:#/.@/; return "\n$e"}
print head reverse despam "moc:xedef#yleen:leoj" ;
