I really appreciate the addition of bind-index in update v4.0.31506 https://opusmodus.com/forums/topic/4133-opusmodus-4031506-update/#comment-14316. This makes reading and comprehending code much easier. Great - thanks @opmo .

Question:

@opmo Can bind-index be modified, such that the arrows feature described below is mimicked?

This would make code even cleaner (at least in case of functions where x is in first argument position.

;; New syntax v4.0.31506
;; Example from https://opusmodus.com/forums/topic/4133-opusmodus-4031506-update/#comment-14316
(bind-index 'mat
  (gen-noise 8 :seed 42)
  (vector-smooth 0.3 x)
  (vector-to-pitch '(c3 c5) x)
  (pitch-transpose 12 x)
  (tonality-map '(major :map 'octave) x)
  (make-omn :pitch x
            :length '(h)
            :span :pitch))
; => (h g4 mf g4 f4 c4 a4 f5 a5 c6)

;; Compare with arrows
(-<>
 (gen-noise 8 :seed 42)
 (vector-smooth 0.3 <>)
 (vector-to-pitch '(c3 c5) <>)
 (pitch-transpose 12 <>)
 (tonality-map '(major :map 'octave) <>)
 (make-omn :pitch <>
           :length '(h)
           :span :pitch))
; => (h g4 mf g4 f4 c4 a4 f5 a5 c6)

;; Summary:
;; bind-index is functionally equivalent to original arrows-syntax :-)
;; except for the fact that bind-index is more powerful
;; as one can refer to an explicite intermediate pipeline result.


;;; ---------------------


;; But there's one feature which has yet not been 
;; carried over from arrows to bind-index
;;
;; arrows has a feature where former pipeline result
;; is implicitely added even if <> is not meantioned
;; this works for functions where <> has 1st argument position

(-<>
 (gen-noise 4 :seed 42)
 (gen-divide 2 <>)
 (flatten)) ;; no x here
; => (0.45572352 0.3392996 0.19626139 0.81495554)

(bind-index 'x-
 (gen-noise 4 :seed 42)
 (gen-divide 2 x)
 (flatten)) ;; no x here
; => throghs an error as x is missing

(bind-index 'x-
 (gen-noise 4 :seed 42)
 (gen-divide 2 x)
 (flatten x)) ;; x included and required currently
; => works
; => (0.45572352 0.3392996 0.19626139 0.81495554)

The bind-index construct is a simple variable assignment and does not attempt to alter standard Common Lisp function forms: (flatten).

I am planning to remove the Arrows library from OM. Users who wish to continue using it will need to install and load it separately through Quicklisp.

Regading arrows removal: Understood, keeping external dependencies minimal is always a good idea.

At the end I am happy that OM has introduced some piping functionality.

Arrows removed in 4.0.31510

You find more score example using bind-index macro in the document and links.

I rewrote several scores using the new bind-index feature to demonstrate how it can be used in both simple and more complex scores.

Links to the relevant scores can be found at the end of the bind-index documentation - 4.0.31513