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while in terms of syntax-case
* module/ice-9/boot-9.scm (while): Reimplement in terms of syntax-case. Prompt inlining is coming later. * test-suite/tests/syntax.test ("while"): Update the expected syntax errors.
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2 changed files with 46 additions and 25 deletions
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@ -2842,28 +2842,46 @@ module '(ice-9 q) '(make-q q-length))}."
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;;; with `continue' and `break'.
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;;;
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;; The inner `do' loop avoids re-establishing a catch every iteration,
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;; that's only necessary if continue is actually used. A new key is
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;; generated every time, so break and continue apply to their originating
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;; `while' even when recursing.
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;; The inliner will remove the prompts at compile-time if it finds that
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;; `continue' or `break' are not used.
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;;
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;; FIXME: This macro is unintentionally unhygienic with respect to let,
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;; make-symbol, do, throw, catch, lambda, and not.
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;;
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(define-macro (while cond . body)
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(let ((keyvar (make-symbol "while-keyvar")))
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`(let ((,keyvar (make-symbol "while-key")))
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(do ()
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((catch ,keyvar
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(lambda ()
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(let ((break (lambda () (throw ,keyvar #t)))
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(continue (lambda () (throw ,keyvar #f))))
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(do ()
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((not ,cond))
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,@body)
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#t))
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(lambda (key arg)
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arg)))))))
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(define-syntax while
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(lambda (x)
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(syntax-case x ()
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((while cond body ...)
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#`(let ((break-tag (make-prompt-tag "break"))
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(continue-tag (make-prompt-tag "continue")))
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(call-with-prompt
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break-tag
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(lambda ()
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(define-syntax #,(datum->syntax #'while 'break)
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(lambda (x)
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(syntax-case x ()
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((_)
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#'(abort-to-prompt break-tag))
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((_ . args)
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(syntax-violation 'break "too many arguments" x))
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(_
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#'(lambda ()
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(abort-to-prompt break-tag))))))
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(let lp ()
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(call-with-prompt
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continue-tag
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(lambda ()
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(define-syntax #,(datum->syntax #'while 'continue)
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(lambda (x)
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(syntax-case x ()
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((_)
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#'(abort-to-prompt continue-tag))
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((_ . args)
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(syntax-violation 'continue "too many arguments" x))
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(_
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#'(lambda args
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(apply abort-to-prompt continue-tag args))))))
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(do () ((not cond)) body ...))
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(lambda (k) (lp)))))
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(lambda (k)
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#t)))))))
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@ -1,6 +1,6 @@
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;;;; syntax.test --- test suite for Guile's syntactic forms -*- scheme -*-
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;;;;
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;;;; Copyright (C) 2001,2003,2004, 2005, 2006, 2009 Free Software Foundation, Inc.
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;;;; Copyright (C) 2001,2003,2004, 2005, 2006, 2009, 2010 Free Software Foundation, Inc.
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;;;;
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;;;; This library is free software; you can redistribute it and/or
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;;;; modify it under the terms of the GNU Lesser General Public
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@ -75,6 +75,9 @@
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(define exception:bad-cond-clause
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(cons 'syntax-error "Bad cond clause"))
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(define exception:too-many-args
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(cons 'syntax-error "too many arguments"))
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(with-test-prefix "expressions"
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@ -832,7 +835,7 @@
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#t))))
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(pass-if-exception "too few args" exception:wrong-num-args
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(pass-if-exception "too few args" exception:generic-syncase-error
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(eval '(while) (interaction-environment)))
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(with-test-prefix "empty body"
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@ -872,7 +875,7 @@
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(with-test-prefix "break"
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(pass-if-exception "too many args" exception:wrong-num-args
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(pass-if-exception "too many args" exception:too-many-args
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(eval '(while #t
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(break 1))
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(interaction-environment)))
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@ -945,7 +948,7 @@
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(with-test-prefix "continue"
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(pass-if-exception "too many args" exception:wrong-num-args
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(pass-if-exception "too many args" exception:too-many-args
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(eval '(while #t
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(continue 1))
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(interaction-environment)))
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