Re: conditional when-property function not working as intended

[Kieren MacMillan]

Hi David,

> But we are not talking about music functions (where the quite different
> "parser location" arguments are now usually passed implicitly) but
> markup commands here.

Ah! That would be the source of my confusion.

Thank you,
Kieren.


Kieren MacMillan, composer
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‣ email: i...@kierenmacmillan.info


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Re: conditional when-property function not working as intended

[Kieren MacMillan]

Hi David,

> By not specifying a default value?  I have absolutely no idea why you
> put `markp' as the default-value of your call to ly:chain-assoc-get.

Because this is somebody else’s code that I’m using, without (obviously) fully 
understanding what it does.
With your hint, I believe I can now modify the code so that it works as I would 
have expected it to in the first place.

Thanks,
Kieren.


Kieren MacMillan, composer
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‣ email: i...@kierenmacmillan.info


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Re: conditional when-property function not working as intended

[David Kastrup]

Kieren MacMillan  writes:

> Hi David,
>
>> It's necessary for functions taking "layout props" arguments?  Where
>> would that cause reason for doubt?
>
> I thought I recalled a recent update (say, in the past 2 years) in
> which those arguments were rendered unnecessary when writing certain
> music functions — but apparently, I’m mistaken.

But we are not talking about music functions (where the quite different
"parser location" arguments are now usually passed implicitly) but
markup commands here.

-- 
David Kastrup

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Re: conditional when-property function not working as intended

[David Kastrup]

Kieren MacMillan  writes:

> Hi David,
>
> Thank you for the helpful reply and documentation/explanation.
>
>> -- Function: ly:chain-assoc-get key achain default-value
>>  strict-checking
>> Return value for KEY from a list of alists ACHAIN.  If no entry is
>> found, return DEFAULT-VALUE or ‘#f’ if DEFAULT-VALUE is not
>> specified.  [...]
>> 
>> DEFAULT-VALUE is specified as markp, and a markup is never #f.  So your
>> condition is always true when the specified KEY cannot be found.
>
> So how could I code the when-property function so that it is false
> when the KEY cannot be found?

By not specifying a default value?  I have absolutely no idea why you
put `markp' as the default-value of your call to ly:chain-assoc-get.  It
does not serve any purpose conceivable to me, particularly since you are
only planning to use its value when finding the key, and the purpose of
the default-value is to be substituted when _not_ finding the key.

-- 
David Kastrup

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Re: conditional when-property function not working as intended

[Kieren MacMillan]

Hi David,

Thank you for the helpful reply and documentation/explanation.

> -- Function: ly:chain-assoc-get key achain default-value
>  strict-checking
> Return value for KEY from a list of alists ACHAIN.  If no entry is
> found, return DEFAULT-VALUE or ‘#f’ if DEFAULT-VALUE is not
> specified.  [...]
> 
> DEFAULT-VALUE is specified as markp, and a markup is never #f.  So your
> condition is always true when the specified KEY cannot be found.

So how could I code the when-property function so that it is false when the KEY 
cannot be found?

Thank you,
Kieren.


Kieren MacMillan, composer
‣ website: www.kierenmacmillan.info
‣ email: i...@kierenmacmillan.info


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Re: conditional when-property function not working as intended

[Kieren MacMillan]

Hi David,

> It's necessary for functions taking "layout props" arguments?  Where
> would that cause reason for doubt?

I thought I recalled a recent update (say, in the past 2 years) in which those 
arguments were rendered unnecessary when writing certain music functions — but 
apparently, I’m mistaken.

Thanks,
Kieren.


Kieren MacMillan, composer
‣ website: www.kierenmacmillan.info
‣ email: i...@kierenmacmillan.info


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Re: conditional when-property function not working as intended

[David Kastrup]

Kieren MacMillan  writes:

> Hi all,
>
> Solved my own problem (I think?): the modified version (below) appears to 
> work as expected.
>
> On a related topic: I [clearly] don’t understand when “layout props”
> is necessary, and when it’s not.

It's necessary for functions taking "layout props" arguments?  Where
would that cause reason for doubt?

-- 
David Kastrup

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Re: conditional when-property function not working as intended

[David Kastrup]

Kieren MacMillan  writes:

> Hello all,
>
> In the snippet included below, I’m hoping the second line of the 
> scoreTitleMarkup will take no vertical space. If you comment out that line, 
> you’ll see that it *does* take no space, but when it’s included, so is the 
> 25mm spacing that is [I thought] conditional on the presence of a ‘testB’ 
> property in the property.
>
> Where is my code going wrong?
> More precisely, how can I make it work as intended?  =)
>
> Thanks,
> Kieren.
>
>   SNIPPET BEGINS
> \version "2.19.46"
>
> #(define-markup-command (when-property layout props symbol markp) (symbol? 
> markup?)
>   (if (chain-assoc-get layout props symbol markp)
>   (interpret-markup layout props markp)
>   empty-stencil))

 -- Function: ly:chain-assoc-get key achain default-value
  strict-checking
 Return value for KEY from a list of alists ACHAIN.  If no entry is
 found, return DEFAULT-VALUE or ‘#f’ if DEFAULT-VALUE is not
 specified.  [...]

DEFAULT-VALUE is specified as markp, and a markup is never #f.  So your
condition is always true when the specified KEY cannot be found.

-- 
David Kastrup

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Re: conditional when-property function not working as intended

[Kieren MacMillan]

Hi all,

Solved my own problem (I think?): the modified version (below) appears to work 
as expected.

On a related topic: I [clearly] don’t understand when “layout props” is 
necessary, and when it’s not.
Is this explained in the docs somewhere?

Thanks,
Kieren.

  SNIPPET BEGINS
\version "2.19.46"

#(define-markup-command (when-property layout props symbol markp) (symbol? 
markup?)
  (if (chain-assoc-get symbol props)
  (interpret-markup layout props markp)
  empty-stencil))

#(define-markup-command (mm-feed layout props amount) (number?)
 (let ((o-s (ly:output-def-lookup layout 'output-scale)))
   (ly:make-stencil "" '(0 . 0) (cons 0 (abs (/ amount o-s))

#(define-markup-command (put-mm layout props dir amount arg)
 (ly:dir? number? markup?) (interpret-markup layout props
   (markup #:put-adjacent Y dir arg #:mm-feed amount)))

\header {
  testA = "True!"
  testC = "True!"
}

\paper {
  scoreTitleMarkup = \markup \center-column {
\when-property #'header:testA { \put-mm #UP #25 \fromproperty 
#'header:testA }
\when-property #'header:testB { \put-mm #UP #25 \fromproperty 
#'header:testB }
\when-property #'header:testC { \put-mm #UP #25 \fromproperty 
#'header:testC }
  }
}

\score {
  c'4
}
  SNIPPET ENDS



Kieren MacMillan, composer
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‣ email: i...@kierenmacmillan.info


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conditional when-property function not working as intended

[Kieren MacMillan]

Hello all,

In the snippet included below, I’m hoping the second line of the 
scoreTitleMarkup will take no vertical space. If you comment out that line, 
you’ll see that it *does* take no space, but when it’s included, so is the 25mm 
spacing that is [I thought] conditional on the presence of a ‘testB’ property 
in the property.

Where is my code going wrong?
More precisely, how can I make it work as intended?  =)

Thanks,
Kieren.

  SNIPPET BEGINS
\version "2.19.46"

#(define-markup-command (when-property layout props symbol markp) (symbol? 
markup?)
  (if (chain-assoc-get layout props symbol markp)
  (interpret-markup layout props markp)
  empty-stencil))

#(define-markup-command (mm-feed layout props amount) (number?)
 (let ((o-s (ly:output-def-lookup layout 'output-scale)))
   (ly:make-stencil "" '(0 . 0) (cons 0 (abs (/ amount o-s))

#(define-markup-command (put-mm layout props dir amount arg)
 (ly:dir? number? markup?) (interpret-markup layout props
   (markup #:put-adjacent Y dir arg #:mm-feed amount)))

\header {
  testA = "True!"
  testC = "True!"
}

\paper {
  scoreTitleMarkup = \markup \center-column {
\when-property #'header:testA { \put-mm #UP #25 \fromproperty 
#'header:testA }
\when-property #'header:testB { \put-mm #UP #25 \fromproperty 
#'header:testB }
\when-property #'header:testC { \put-mm #UP #25 \fromproperty 
#'header:testC }
  }
}

\score {
  c'4
}
  SNIPPET ENDS



Kieren MacMillan, composer
‣ website: www.kierenmacmillan.info
‣ email: i...@kierenmacmillan.info


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