I was trying to test some ideas and was using the new FullBlockClosure to return values for further use in a workspace.
This works with “print it”:
[Transcript show: 2;cr. ^2] value => 2
This does not work:
test := [Transcript show: 2;cr. ^2] value <do it>
test => nil.
nor does this:
test :=( [Transcript show: 2;cr. ^2] value) <do it>
test => nil
print it still works:
test := ([Transcript show: 2;cr. ^2] value) => 2
test => nil.
In all cases, a 2 appears in the Transcript window, so I know that *something* is happening.
I would have thought that if print-it and do-it work, then the returned value would be put in the test variable, but that is not the case.
I can use a workspace global variable to access the output, but that kinda makes the ^ a one-trick-pony: useful for breaking out of loops, but not giving me access to the return value.
[test := 2. Transcript show: test;cr. ^test] value => 2
test => 2
Is this an oversight or bug or feature for workspaces, or is it working as intended?
Lawson
Hi Lawson
good to see you.
On 28. Nov 2022, at 11:58, LawsonEnglish LEnglish5@cox.net wrote:
I was trying to test some ideas and was using the new FullBlockClosure to return values for further use in a workspace.
This works with “print it”:
[Transcript show: 2;cr. ^2] value => 2
This does not work:
test := [Transcript show: 2;cr. ^2] value <do it>
test => nil.
Yes, and that is expected.
Two things: First, it seems you want to assign the _return value_ of a block to a variable. To achieve this, do test := [Transcript show: 2;cr. 2] value "Note the missing caret/return"
This is because the last statement of a block will be its return value.
Second, yes, the return/caret in the block does something but apparently not the thing you expected. The effect for caret/^/return is:
^ statement "Returns the value from statement from the method"
The last word is crucial. You return from the method, regardless of the block you are in.
Like so:
fooo
Transcript showln: 'foo 1'. self bar: [Transcript showln: 'block 1'. ^ 1]. Transcript showln: 'foo 2'. ^ 2.
bar: aBlock
Transcript showln: 'bar 1'. aBlock value. Transcript showln: 'bar 2'.
If you send #foo, transcript will contain
foo 1 bar 1 block 1
an the return value will be 1.
This is because the Return in the block will return form the _method #foo_ (where the block is defined) and not only from the block.
What does that have to do with the Workspace???
Workspaces create artificial methods for doIts and PrintIts.
Hence, your actually sent method looks like that:
DoIt test := [Transcript show: 2;cr. ^2] value
If you run that method as print-it, "^2" returns form the DoIt method and the workspace can print the 2. If you run that method as print-it, "^2" returns form the DoIt method but the assignment has never taken place, so test remains at its previous value, wich is nil.
I hope this helps.
Best regards -Tobias
nor does this:
test :=( [Transcript show: 2;cr. ^2] value) <do it>
test => nil
print it still works:
test := ([Transcript show: 2;cr. ^2] value) => 2
test => nil.
In all cases, a 2 appears in the Transcript window, so I know that *something* is happening.
I would have thought that if print-it and do-it work, then the returned value would be put in the test variable, but that is not the case.
I can use a workspace global variable to access the output, but that kinda makes the ^ a one-trick-pony: useful for breaking out of loops, but not giving me access to the return value.
[test := 2. Transcript show: test;cr. ^test] value => 2
test => 2
Is this an oversight or bug or feature for workspaces, or is it working as intended?
Lawson
OK, thanks.
I had thought perhaps it would act more like a break and take one to the outside of the block, but instead it returns to the caller, as I should have realized.
Stilly me.
L
On Nov 28, 2022, at 04:15, Tobias Pape Das.Linux@gmx.de wrote:
Hi Lawson
good to see you.
On 28. Nov 2022, at 11:58, LawsonEnglish LEnglish5@cox.net wrote:
I was trying to test some ideas and was using the new FullBlockClosure to return values for further use in a workspace.
This works with “print it”:
[Transcript show: 2;cr. ^2] value => 2
This does not work:
test := [Transcript show: 2;cr. ^2] value <do it>
test => nil.
Yes, and that is expected.
Two things: First, it seems you want to assign the _return value_ of a block to a variable. To achieve this, do test := [Transcript show: 2;cr. 2] value "Note the missing caret/return"
This is because the last statement of a block will be its return value.
Second, yes, the return/caret in the block does something but apparently not the thing you expected. The effect for caret/^/return is:
^ statement "Returns the value from statement from the method"
The last word is crucial. You return from the method, regardless of the block you are in.
Like so:
fooo
Transcript showln: 'foo 1'. self bar: [Transcript showln: 'block 1'. ^ 1]. Transcript showln: 'foo 2'. ^ 2.
bar: aBlock
Transcript showln: 'bar 1'. aBlock value. Transcript showln: 'bar 2'.
If you send #foo, transcript will contain
foo 1 bar 1 block 1
an the return value will be 1.
This is because the Return in the block will return form the _method #foo_ (where the block is defined) and not only from the block.
What does that have to do with the Workspace???
Workspaces create artificial methods for doIts and PrintIts.
Hence, your actually sent method looks like that:
DoIt test := [Transcript show: 2;cr. ^2] value
If you run that method as print-it, "^2" returns form the DoIt method and the workspace can print the 2. If you run that method as print-it, "^2" returns form the DoIt method but the assignment has never taken place, so test remains at its previous value, wich is nil.
I hope this helps.
Best regards -Tobias
nor does this:
test :=( [Transcript show: 2;cr. ^2] value) <do it>
test => nil
print it still works:
test := ([Transcript show: 2;cr. ^2] value) => 2
test => nil.
In all cases, a 2 appears in the Transcript window, so I know that *something* is happening.
I would have thought that if print-it and do-it work, then the returned value would be put in the test variable, but that is not the case.
I can use a workspace global variable to access the output, but that kinda makes the ^ a one-trick-pony: useful for breaking out of loops, but not giving me access to the return value.
[test := 2. Transcript show: test;cr. ^test] value => 2
test => 2
Is this an oversight or bug or feature for workspaces, or is it working as intended?
Lawson
I read somewhere to never write ^ in a block you intend to give out. I use it to abandon methods in assertions and never any other time.
One thing I do know from experimentation is it marks the method finished, so you can't call the block twice. You'll get BlockCannotReturn nowadays. It used to be a segmentation fault.
On Mon, Nov 28, 2022, 04:33 LawsonEnglish LEnglish5@cox.net wrote:
OK, thanks.
I had thought perhaps it would act more like a break and take one to the outside of the block, but instead it returns to the caller, as I should have realized.
Stilly me.
L
On Nov 28, 2022, at 04:15, Tobias Pape Das.Linux@gmx.de wrote:
Hi Lawson
good to see you.
On 28. Nov 2022, at 11:58, LawsonEnglish LEnglish5@cox.net wrote:
I was trying to test some ideas and was using the new FullBlockClosure
to return values for further use in a workspace.
This works with “print it”:
[Transcript show: 2;cr. ^2] value => 2
This does not work:
test := [Transcript show: 2;cr. ^2] value <do it>
test => nil.
Yes, and that is expected.
Two things: First, it seems you want to assign the _return value_ of a block to a
variable.
To achieve this, do test := [Transcript show: 2;cr. 2] value "Note the missing
caret/return"
This is because the last statement of a block will be its return value.
Second, yes, the return/caret in the block does something but apparently
not the thing you expected.
The effect for caret/^/return is:
^ statement "Returns the value from statement from the method"The last word is crucial. You return from the method, regardless of the
block you are in.
Like so:
fooo
Transcript showln: 'foo 1'. self bar: [Transcript showln: 'block 1'. ^ 1]. Transcript showln: 'foo 2'. ^ 2.
bar: aBlock
Transcript showln: 'bar 1'. aBlock value. Transcript showln: 'bar 2'.
If you send #foo, transcript will contain
foo 1 bar 1 block 1
an the return value will be 1.
This is because the Return in the block will return form the _method
#foo_ (where the block is defined) and not only from the block.
What does that have to do with the Workspace???
Workspaces create artificial methods for doIts and PrintIts.
Hence, your actually sent method looks like that:
DoIt test := [Transcript show: 2;cr. ^2] value
If you run that method as print-it, "^2" returns form the DoIt method
and the workspace can print the 2.
If you run that method as print-it, "^2" returns form the DoIt method
but the assignment has never taken place, so test remains at its previous value, wich is nil.
I hope this helps.
Best regards -Tobias
nor does this:
test :=( [Transcript show: 2;cr. ^2] value) <do it>
test => nil
print it still works:
test := ([Transcript show: 2;cr. ^2] value) => 2
test => nil.
In all cases, a 2 appears in the Transcript window, so I know that
*something* is happening.
I would have thought that if print-it and do-it work, then the
returned value would be put in the test variable, but that is not the case.
I can use a workspace global variable to access the output, but that
kinda makes the ^ a one-trick-pony: useful for breaking out of loops, but not giving me access to the return value.
[test := 2. Transcript show: test;cr. ^test] value => 2
test => 2
Is this an oversight or bug or feature for workspaces, or is it working
as intended?
Lawson
If you want to return from the block directly (but not from the containing method), here are some options:
[:x | x ifNil: [#plonk] ifNotNil: [x + 1]].
[:x | x ifNil: [thisContext return: #plonk] ifNotNil: [x + 1]]. "metaprogramming, usually disregarded!"
Best,
Christoph
________________________________ Von: Squeak-dev squeak-dev-bounces@lists.squeakfoundation.org im Auftrag von Lauren P drurowin@gmail.com Gesendet: Montag, 28. November 2022 18:01:42 An: The general-purpose Squeak developers list Betreff: Re: [squeak-dev] Full block closure return value testing/using in workspace?
I read somewhere to never write ^ in a block you intend to give out. I use it to abandon methods in assertions and never any other time.
One thing I do know from experimentation is it marks the method finished, so you can't call the block twice. You'll get BlockCannotReturn nowadays. It used to be a segmentation fault.
On Mon, Nov 28, 2022, 04:33 LawsonEnglish <LEnglish5@cox.netmailto:LEnglish5@cox.net> wrote: OK, thanks.
I had thought perhaps it would act more like a break and take one to the outside of the block, but instead it returns to the caller, as I should have realized.
Stilly me.
L
On Nov 28, 2022, at 04:15, Tobias Pape <Das.Linux@gmx.demailto:Das.Linux@gmx.de> wrote:
Hi Lawson
good to see you.
On 28. Nov 2022, at 11:58, LawsonEnglish <LEnglish5@cox.netmailto:LEnglish5@cox.net> wrote:
I was trying to test some ideas and was using the new FullBlockClosure to return values for further use in a workspace.
This works with “print it”:
[Transcript show: 2;cr. ^2] value => 2
This does not work:
test := [Transcript show: 2;cr. ^2] value <do it>
test => nil.
Yes, and that is expected.
Two things: First, it seems you want to assign the _return value_ of a block to a variable. To achieve this, do test := [Transcript show: 2;cr. 2] value "Note the missing caret/return"
This is because the last statement of a block will be its return value.
Second, yes, the return/caret in the block does something but apparently not the thing you expected. The effect for caret/^/return is:
^ statement "Returns the value from statement from the method"The last word is crucial. You return from the method, regardless of the block you are in.
Like so:
fooo
Transcript showln: 'foo 1'. self bar: [Transcript showln: 'block 1'. ^ 1]. Transcript showln: 'foo 2'. ^ 2.
bar: aBlock
Transcript showln: 'bar 1'. aBlock value. Transcript showln: 'bar 2'.
If you send #foo, transcript will contain
foo 1 bar 1 block 1
an the return value will be 1.
This is because the Return in the block will return form the _method #foo_ (where the block is defined) and not only from the block.
What does that have to do with the Workspace???
Workspaces create artificial methods for doIts and PrintIts.
Hence, your actually sent method looks like that:
DoIt test := [Transcript show: 2;cr. ^2] value
If you run that method as print-it, "^2" returns form the DoIt method and the workspace can print the 2. If you run that method as print-it, "^2" returns form the DoIt method but the assignment has never taken place, so test remains at its previous value, wich is nil.
I hope this helps.
Best regards -Tobias
nor does this:
test :=( [Transcript show: 2;cr. ^2] value) <do it>
test => nil
print it still works:
test := ([Transcript show: 2;cr. ^2] value) => 2
test => nil.
In all cases, a 2 appears in the Transcript window, so I know that *something* is happening.
I would have thought that if print-it and do-it work, then the returned value would be put in the test variable, but that is not the case.
I can use a workspace global variable to access the output, but that kinda makes the ^ a one-trick-pony: useful for breaking out of loops, but not giving me access to the return value.
[test := 2. Transcript show: test;cr. ^test] value => 2
test => 2
Is this an oversight or bug or feature for workspaces, or is it working as intended?
Lawson
squeak-dev@lists.squeakfoundation.org
-
Lauren P -
LawsonEnglish -
Thiede, Christoph -
Tobias Pape