Hi Thomas,
Thank you the solution, and for explaining how. I learned a lot from this!
Kevin
On Sun, Mar 15, 2015 at 9:27 PM, Thomas Morley <thomasmorle...@gmail.com>
wrote:
>
>
> 2015-03-15 22:07 GMT+01:00 Thomas Morley <thomasmorle...@gmail.com>:
>
>>
>>
>> 2015-03-15 21:48 GMT+01:00 Kevin Barry <barr...@gmail.com>:
>>
>>> Hi LilyPond experts,
>>>
>>> I'm trying to make a function that will draw a curved line given only a
>>> destination point (with some math I'll add later), but I've hit an early
>>> stumbling block: I can't seem to substitute variables for values in the
>>> path/curveto command list. The following code produces a
>>> `wrong-argument-type' error, but it points to scm/stencil.scm which isn't
>>> very helpful for figuring out what's wrong. Help appreciated!
>>>
>>> \version "2.18.2"
>>>
>>> #(define-markup-command (draw-curved-line layout props points)
>>> (number-pair?)
>>> (let ((xpt (car points))
>>> (ypt (cdr points)))
>>> (interpret-markup layout props
>>> (markup #:path 1 '((curveto 0 ypt 0 ypt xpt ypt))))))
>>>
>>> \relative {
>>> b_\markup { \draw-curved-line #'(5 . 5) }
>>> }
>>>
>>>
>> Hi Kevin,
>>
>> in cases where i have no clue what's wrong and don't understand the
>> error-message, I boil down the code and display all kind of data, values,
>> ets
>>
>> In your case I'd do:
>>
>> #(define-markup-command (draw-curved-line layout props points)
>> (number-pair?)
>> (let ((xpt (car points))
>> (ypt (cdr points)))
>>
>> (display '((curveto 0 ypt 0 ypt xpt ypt)))
>> (newline)
>> (display (caddar '((curveto 0 ypt 0 ypt xpt ypt))))
>> (newline)
>> (display (symbol? (caddar '((curveto 0 ypt 0 ypt xpt ypt)))))
>>
>>
>> (interpret-markup layout props
>> (markup
>> ;#:path 1 '((curveto 0 ypt 0 ypt xpt ypt))
>> "xy"
>> ))
>> ))
>>
>>
>>
>> The problem should be clear now: the variables in '((curveto 0 ypt 0 ypt
>> xpt ypt)) are not evaluated but taken as symbols.
>> You wrote a quoted list, but need some elements of the list be unquoted.
>> Shortest: use a combi of ` and ,
>>
>>
>> #(define-markup-command (draw-curved-line layout props points)
>> (number-pair?)
>> (let ((xpt (car points))
>> (ypt (cdr points)))
>> (interpret-markup layout props
>> (markup
>> #:path 1 `((curveto 0 ,ypt 0 ,ypt ,xpt ,ypt))
>>
>
> other syntax-possibilities:
> (list (list 'curveto 0 ypt 0 ypt xpt ypt))
> or most verbose:
> (quasiquote
> ((curveto 0 (unquote ypt) 0 (unquote ypt) (unquote xpt) (unquote ypt))))
>
> Look up 'quote', 'unquote', 'quasiquote' etc in the guile manual
>
> ))))
>>
>>
>>
>> HTH,
>> Harm
>>
>>
>
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