69 lines
2.1 KiB
Scheme
69 lines
2.1 KiB
Scheme
;; All implementations here are "borrowed" from
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;; husk-scheme (github.com/justinethier/husk-scheme).
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(define-syntax let
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(syntax-rules ()
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((_ ((x v) ...) e1 e2 ...)
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((lambda (x ...) e1 e2 ...) v ...))
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((_ name ((x v) ...) e1 e2 ...)
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(let*
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((f (lambda (name)
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(lambda (x ...) e1 e2 ...)))
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(ff ((lambda (proc) (f (lambda (x ...) ((proc proc)
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x ...))))
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(lambda (proc) (f (lambda (x ...) ((proc proc)
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x ...)))))))
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(ff v ...)))))
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(define-syntax let*
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(syntax-rules ()
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((let* () body1 body2 ...)
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(let () body1 body2 ...))
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((let* ((name1 val1) (name2 val2) ...)
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body1 body2 ...)
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(let ((name1 val1))
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(let* ((name2 val2) ...)
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body1 body2 ...)))))
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(define-syntax letrec
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(syntax-rules ()
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((letrec ((var1 init1) ...) body ...)
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(letrec "generate_temp_names"
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(var1 ...)
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()
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((var1 init1) ...)
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body ...))
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((letrec "generate_temp_names"
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()
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(temp1 ...)
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((var1 init1) ...)
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body ...)
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(let ((var1 #f) ...)
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(let ((temp1 init1) ...)
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(set! var1 temp1)
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...
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body ...)))
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((letrec "generate_temp_names"
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(x y ...)
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(temp ...)
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((var1 init1) ...)
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body ...)
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(letrec "generate_temp_names"
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(y ...)
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(newtemp temp ...)
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((var1 init1) ...)
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body ...))))
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(define-syntax do
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(syntax-rules ()
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((_ ((var init . step) ...)
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(test expr ...)
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command ...)
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(let loop ((var init) ...)
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(if test
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(begin expr ...)
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(begin (begin command ...)
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(loop
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(if (null? (cdr (list var . step)))
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(car (list var . step))
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(cadr (list var . step))) ...)))))))
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