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#valueWithExit inconsistency (?)

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Jaromir Matas

#valueWithExit inconsistency (?)

Current implementation of #valueWithExit seems a bit inconsistent in its
return value: it returns either nil (if the receiver exited using the exit
block) or the receiver.

Would it be worth modifying it to always return nil? (there are no senders
anyway)

valueWithExit
- self value: [ ^nil ]
+ ^self value: [ ^nil ]

Or using a nice complementary method #valueWithExit:

valueWithExit: aBlock
self value: [^aBlock value].
^aBlock value

valueWithExit
^self valueWithExit: [nil]

Thanks

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Jaromir
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marcel.taeumel

Re: #valueWithExit inconsistency (?)

Hi Jaromir.

I added commentary via Kernel-mt.1370. I don't think that the (outer block's) return value should ever be used in this construct. It is more like a #detect: but without meaningful return values.

http://forum.world.st/explicit-return-from-a-block-tp51833.html

http://forum.world.st/The-Trunk-Kernel-ul-519-mcz-td3077583.html

I don't suppose it is idiomatic Smalltalk: "...but actually, I never had any reason to use this except when porting algorithms from Fortran or C... "

Best,

Marcel

Am 16.02.2021 14:05:23 schrieb Jaromir <[hidden email]>:
Current implementation of #valueWithExit seems a bit inconsistent in its
return value: it returns either nil (if the receiver exited using the exit
block) or the receiver.

Would it be worth modifying it to always return nil? (there are no senders
anyway)

valueWithExit
- self value: [ ^nil ]
+ ^self value: [ ^nil ]

Or using a nice complementary method #valueWithExit:

valueWithExit: aBlock
self value: [^aBlock value].
^aBlock value

valueWithExit
^self valueWithExit: [nil]

Thanks

-----
Jaromir
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Sent from: http://forum.world.st/Squeak-Dev-f45488.html

Eliot Miranda-2

Re: #valueWithExit inconsistency (?)

On Wed, Feb 17, 2021 at 8:52 AM Marcel Taeumel <[hidden email]> wrote:

Hi Jaromir.

I added commentary via Kernel-mt.1370. I don't think that the (outer block's) return value should ever be used in this construct. It is more like a #detect: but without meaningful return values.

http://forum.world.st/explicit-return-from-a-block-tp51833.html
http://forum.world.st/The-Trunk-Kernel-ul-519-mcz-td3077583.html

I don't suppose it is idiomatic Smalltalk: "...but actually, I never had any reason to use this except when porting algorithms from Fortran or C... "

But there's a bug. It should at least answer the result of value:. I'm going to change it.

Best,
Marcel

Am 16.02.2021 14:05:23 schrieb Jaromir <[hidden email]>:
Current implementation of #valueWithExit seems a bit inconsistent in its
return value: it returns either nil (if the receiver exited using the exit
block) or the receiver.

Would it be worth modifying it to always return nil? (there are no senders
anyway)

valueWithExit
- self value: [ ^nil ]
+ ^self value: [ ^nil ]

Or using a nice complementary method #valueWithExit:

valueWithExit: aBlock
self value: [^aBlock value].
^aBlock value

valueWithExit
^self valueWithExit: [nil]

Thanks

-----
Jaromir
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Sent from: http://forum.world.st/Squeak-Dev-f45488.html

_,,,^..^,,,_

best, Eliot

Jaromir Matas

Re: #valueWithExit inconsistency (?)

Hi, thanks for your feedback! I'm by no means advocating for using returns
from blocks :) I just found it useful in understanding the local vs.
non-local returns... e.g. in this example the return value is useful:

"find max value before nil and return its square"
| supplier max maxSquared |
supplier := {3 . 2 . 5 . 1 . nil . 6} readStream.
maxSquared := [:exitBlock | | value |
max := 0.
[supplier atEnd]
whileFalse: [
value := supplier next.
value ifNil: [exitBlock value].
max := max max: value]
] valueWithExit: [max squared].
"more code"
Transcript show: maxSquared

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Jaromir
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