Dear friends
A few days ago, I asked whether anyone knows how one can use variable parameter
lists = optional arguments = flexible argumentlists in a markup function. I was
told that such an opportunity does not exist (Thomas Morley) resp. must be
simulated by some embedded property features (Urs Liska). Many thanks for these
quick answers. They preserved me from doing unnecessary work.
Here is a pure scheme / guile solution using lisp association lists (demoed by
using the box example from the extend tutorial). The target is, that the users
of
our function may insert the arguments they really need (without having to deal
with those, they do not need) and that they may insert the arguments they want
to
use in the order they prefer [The running version is attached as a file. Each
substantial portions of the code is distributed under the terms of the MIT
license. I assume that the function shall be interpreted on the lilypond
level]:
First, we should define the keys, we want to use (they must be communicated to
the
users of our function)
#(define ka "k1")
#(define kb "k2")
#(define kc "k3")
#(define kd "k4")
#(define ke "k5")
Second, we should define the respective default values
#(define dva "blank") ; a filled string
#(define dvb "") ; an empty string
#(define dvc '()) ; a null value
#(define dvd "blank") ;
#(define dve "") ;
Third, we need a function - let us name it "assign" (you will understand in a
short time, why) - which takes a key, an associationlist (alist) and a default
value. If the alist contains any pair with the same key, then function shall
return the corresponding value, otherwise the given default value
#(define (assign keyValue assocList defaultValue)
(string? list?)
(let* ((localPair (assoc keyValue assocList)))
(if localPair (cdr localPair) defaultValue)
)
)
Based on this pre-work, we can now define a markup function. In the beginning we
define the local parameter variables and let them be instantiated by our assign
function. Then we manipulate the given values in any way. And finally we return
-
as a markup 'object' - a box containing the result of our manipulation:
#(define-markup-command (mybox layout props AL)
(list?)
(let*
( (la (assign ka AL dva))
(lb (assign kb AL dvb))
(lc (assign kc AL dvc))
(ld (assign kd AL dvd))
(le (assign ke AL dve))
(lresult "result")
)
; because we used an empty list (nil) as default value
(if (eq? lc '()) (set! lc ""))
; our 'manupilation' is norhing else but a concatenation ;-)
(set! lresult (string-append la lb lc ld le))
(interpret-markup layout props
#{
\markup \box { #lresult }
#}
)
)
)
This function can be called in any markup context like
\markup \mybox #'(("k5" . "V5")("k1" . "V1"))
The result is a box containing the text "V1blankV5": V1 is given by the second
(sic!) argument - the values of the possible keys k2 and k3 are ignored, because
their default values are "" and an empty list = null - the blank is default
value
of the unused key k4, and V5 is given by the first (sic!) argument.
best regards Karsten
--
Karsten Reincke /\/\ (+49|0) 170 / 927 78 57
Im Braungeröll 31 >oo< mailto:[email protected]
60431 Frankfurt a.M. \/ http://www.fodina.de/kr/
\version "2.18.2"
% A pure scheme / guile solution to define a LilyPond markup
% command with a variable list of arguments by using a
% technique of lisp scheme / guile called association lists
% (demoed by using the box example from the extend tutorial).
% The target is, that the users of the function may insert
% the arguments they really need (without having to deal with
% those, they do not need) and that they may insert the arguments
% they want to use in the order they prefer
% feel free to adopt this example under the following terms:
% Copyright 2019 Karsten Reincke, Frankfurt
% Permission is hereby granted, free of charge, to any person
% obtaining a copy of this software and associated documentation
% files (the "Software"), to deal in the Software without
% restriction, including without limitation the rights to use,
% copy, modify, merge, publish, distribute, sublicense, and/or sell
% copies of the Software, and to permit persons to whom the
% Software is furnished to do so, subject to the following conditions:
% The above copyright notice and this permission notice shall be
% included in all copies or substantial portions of the Software.
% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
% EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
% OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
% NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
% HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
% WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
% FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
% OR OTHER DEALINGS IN THE SOFTWARE.
% 1) we should define the keys, we want to use
% (they must be communicated to the users of our function
#(define ka "k1")
#(define kb "k2")
#(define kc "k3")
#(define kd "k4")
#(define ke "k5")
% 2) we should define the respective default values
#(define dva "blank") % a filled string
#(define dvb "") % an empty string
#(define dvc '()) % a null value
#(define dvd "blank") % a filled string
#(define dve "") % an empty string
% 3) we need a function - let us name it "assign"
% (you will understand in a short time, why) - which takes
% a key, an association list (alist) and a default value.
% If the alist contains any pair with the same key,
% then function shall return the corresponding value,
% otherwise the given default value
#(define (assign keyValue assocList defaultValue)
(string? list?)
(let* ((localPair (assoc keyValue assocList)))
(if localPair (cdr localPair) defaultValue)
)
)
% Based on this pre-work, we can now define a markup function
% with a flexible variable parameter list:
% a) At the beginning we define the local parameter variables
% and let them be instantiated by our assign function.
% b) Then we manipulate the given values in any way.
% c) And finally we return - as a markup 'object' -
% a box containing the result of our manipulation:
#(define-markup-command (mybox layout props AL)
(list?)
(let*
( (la (assign ka AL dva))
(lb (assign kb AL dvb))
(lc (assign kc AL dvc))
(ld (assign kd AL dvd))
(le (assign ke AL dve))
(lresult "result")
)
; because we used an empty list (nil) as default value
(if (eq? lc '()) (set! lc ""))
; our 'manupilation' is a concatenation ;-)
(set! lresult (string-append la lb lc ld le))
(interpret-markup layout props
#{
\markup \box { #lresult }
#}
)
)
)
\markup \mybox #'(("k5" . "V5")("k1" . "V1"))
