3rdparties/software/alexandria-20200427-git/alexandria-2/control-flow.lisp (1227 bytes)
1 (in-package :alexandria-2) 2 3 (defun line-up-iter (thread-first-p acc forms) 4 "Iterative implementation for `thread-iter'. 5 6 The THREAD-FIRST-P decides where to thread the FORMS, accumulating in ACC." 7 (if forms 8 (line-up-iter thread-first-p 9 (let ((form (car forms))) 10 (if (listp form) 11 (if thread-first-p 12 (apply #'list (car form) acc (cdr form)) 13 (append form (cons acc nil))) 14 (list form acc))) 15 (cdr forms)) 16 acc)) 17 18 (defmacro line-up-first (&rest forms) 19 "Lines up FORMS elements as the first argument of their successor. 20 Example: 21 22 (thread-first 23 5 24 (+ 20) 25 / 26 (+ 40)) 27 28 is equivalent to: 29 30 (+ (/ (+ 5 20)) 40) 31 32 Note how the single '/ got converted into a list before 33 threading." 34 (line-up-iter t (car forms) (cdr forms))) 35 36 (defmacro line-up-last (&rest forms) 37 "Lines up FORMS elements as the last argument of their successor. 38 Example: 39 40 (thread-last 41 5 42 (+ 20) 43 / 44 (+ 40)) 45 46 is equivalent to: 47 48 (+ 40 (/ (+ 20 5))) 49 50 Note how the single '/ got converted into a list before 51 threading." 52 (line-up-iter nil (car forms) (cdr forms)))