learning-sicp

My embarrassing half assed SICP run.
git clone https://kaka.farm/~git/learning-sicp
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exercise-4.scm (746B)

      1 (define-library (sicp solutions chapter-1 exercise-4)
      2   (import (scheme base))
      3   (import (srfi srfi-64))
      4   (export
      5    a-plus-abs-b
      6    a-plus-abs-b-2)
      7 
      8   (begin
      9     (define (a-plus-abs-b a b)
     10       ((if (> b 0) + -) a b))
     11 
     12     ;; The result of the "if" expression will be either the procedure "+" or
     13     ;; the procedure "-", which is then applied to "a" and "b".
     14 
     15     ;; a-plus-abs-b, when b > 0, is (+ a b), which is equivalent to (+
     16     ;; a (+ b))
     17     ;;
     18     ;; when b = 0, (- a 0), which is equivalent to (+ a 0)
     19     ;;
     20     ;; and a when b <= 0, (- a b), equivalent to (+ a (- b))
     21 
     22     ;; Considering the definition of the absolute function, we could
     23     ;; replace a-plus-abs-b with:
     24 
     25     (define (a-plus-abs-b-2 a b)
     26       (+ a (abs b)))))