On 2020-02-06 6:10 am, Paolo Prete wrote:
(code)
A few comments on the code:
1) "begin" is used to specify multiple expressions in a construct that
only accepts one. "if" would be an example where "begin" could be
useful; but "let", like many other constructs, already accepts a list of
expressions to evaluate.
;;;;
(define (foo a)
(let ((b (1+ a)))
(begin
(do-something a)
(do-something b))))
;; ...would become...
(define (foo a)
(let ((b (1+ a)))
(do-something a)
(do-something b)))
;;;;
2) "let" without any bindings would be superfluous syntax.
;;;;
(define (foo a)
(let ()
(do-something a)))
;; ...would become...
(define (foo a)
(do-something a))
;;;;
3) "cond" is best used when there are more than two paths, otherwise
"if" is more concise.
;;;;
(define (foo a)
(cond ((< 0 a) (do-something a))
(else (do-another-thing a))))
;; ...would become...
(define (foo a)
(if (< 0 a) (do-something a)
(do-another-thing a)))
;;;;
4) ly:dir? and symbol-list? are built-in type predicates useful for
directions and grob paths, respectively. These can replace your current
use of strings as inputs, which eliminates some potentially unsightly
quotation marks in the user code.
5) Event functions let the user specify direction with the normal syntax
(^, -, _), potentially obviating the need for a direction argument:
%%%%
\version "2.19.83"
foo = #(define-event-function (color) (color?)
#{ -\tweak color #color -\markup "foo" #})
{ b'4 ^\foo #red b'4 _\foo #blue }
%%%%
-- Aaron Hill
