Genloops.
; In third post in this "generated" serial, I'll define "generated"
; versions of loops. By generated, I mean that you use them as
; normal loops, and they substitute normal symbols with generated
; symbols.
;
; The loops for, doargs, dolist, dostring, dotimes and dotree have
; same syntax:
;
; (<loopname> (<symbol> ...) body)
;
;
; I'll try to define genfor, gendoargs, gendolist, gendostring and
; gendotimes so they are used on the following way:
;
;
; (gen<loopname> (<symbol> ...) <body>)
; ^
; |
; only "gen" is inserted, analogously to gensym.
;
;
; Such "generated loops" should be evaluated like
;
;
; (genlocal(<symbol>)
; (<loopname>(<symbol> ...) <body>))
;
;
; Definitions of gensym and genlocal pasted from previous post:
(set 'gensym-counter 0)
(set 'gensym
(lambda(i)
(inc gensym-counter)
(sym (append "("
(string i)
" - "
(string gensym-counter)
". generated symbol)"))))
(set 'genlocal
(lambda-macro(head)
(let ((body (args)))
(letex ((H1 (map (lambda(x)
(list x
(list 'gensym
(list 'quote x))))
head))
(H2 (cons 'local (cons head body)))
(H3 (cons 'begin
(map (lambda(x)
(list 'delete
(list 'quote
x)))
head))))
(letex H1
(first (list H2
H3)))))))
; Definition of "generated loops" genfor, gendoarg, gendolist,
; gendostring, gendotimes so they behave like described above.
; Again, code is complicated but technical, but idea is important.
(dolist (loopname '(for doargs dolist dostring dotimes))
(set (sym (append "gen" (string loopname))) ; for -> genfor etc
(letex ((loopname loopname))
(lambda-macro(head)
(let ((body (args)))
(letex((H1 (list (first head)))
(H2 (append (list 'loopname head) body)))
(genlocal H1
H2)))))))
; Next, I'll memorize (symbols), to show that that all generated
; symobls will be actually, cleaned.
(set 'symbols-before-genloops (symbols))
; Tests that new genfors really work:
(genfor (i 10 20 5)
(println 'i " = " i))
(println)
(gendolist (j '(a b c))
(println 'j " = " j))
(println)
(gendotimes(k 4)(println 'k " = " k))
(println)
; OUTPUT
; (i - 1. generated symbol) = 10
; (i - 1. generated symbol) = 15
; (i - 1. generated symbol) = 20
; (j - 2. generated symbol) = a
; (j - 2. generated symbol) = b
; (j - 2. generated symbol) = c
; (k - 3. generated symbol) = 0
; (k - 3. generated symbol) = 1
; (k - 3. generated symbol) = 2
; (k - 3. generated symbol) = 3
; Test that gensyms are deleted:
(println (difference (symbols) symbols-before-genloops))
; OUTPUT
;
; (a b c j k)
;
; OK.
(exit)
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