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243 lines
9.4 KiB
Scheme
243 lines
9.4 KiB
Scheme
;;;; r4rs.scm --- definitions needed for libguile to be R4RS compliant
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;;;; Jim Blandy <jimb@cyclic.com> --- October 1996
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;;;; Copyright (C) 1996, 1997, 1998, 2000, 2001, 2006, 2010, 2011, 2012 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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;;;; License as published by the Free Software Foundation; either
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;;;; version 3 of the License, or (at your option) any later version.
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;;;;
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;;;; This library is distributed in the hope that it will be useful,
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;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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;;;; Lesser General Public License for more details.
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;;;;
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;;;; You should have received a copy of the GNU Lesser General Public
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;;;; License along with this library; if not, write to the Free Software
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;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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(eval-when (compile)
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(set-current-module (resolve-module '(guile))))
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;;;; apply and call-with-current-continuation
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;;; The deal with these is that they are the procedural wrappers around the
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;;; primitives of Guile's language. There are about 20 different kinds of
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;;; expression in Guile, and e.g. @apply is one of them. (It has to be that way
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;;; to preserve tail recursion.)
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;;;
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;;; Usually we recognize (apply foo bar) to be an instance of @apply, but in the
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;;; case that apply is passed to apply, or we're bootstrapping, we need a
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;;; trampoline -- and here they are.
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(define (apply fun . args)
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(@apply fun (apply:nconc2last args)))
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(define (call-with-current-continuation proc)
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(@call-with-current-continuation proc))
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(define (call-with-values producer consumer)
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(@call-with-values producer consumer))
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(define (dynamic-wind in thunk out)
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"All three arguments must be 0-argument procedures.
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Guard @var{in} is called, then @var{thunk}, then
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guard @var{out}.
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If, any time during the execution of @var{thunk}, the
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continuation of the @code{dynamic_wind} expression is escaped
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non-locally, @var{out} is called. If the continuation of
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the dynamic-wind is re-entered, @var{in} is called. Thus
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@var{in} and @var{out} may be called any number of
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times.
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@lisp
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(define x 'normal-binding)
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@result{} x
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(define a-cont
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(call-with-current-continuation
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(lambda (escape)
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(let ((old-x x))
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(dynamic-wind
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;; in-guard:
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;;
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(lambda () (set! x 'special-binding))
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;; thunk
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;;
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(lambda () (display x) (newline)
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(call-with-current-continuation escape)
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(display x) (newline)
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x)
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;; out-guard:
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;;
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(lambda () (set! x old-x)))))))
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;; Prints:
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special-binding
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;; Evaluates to:
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@result{} a-cont
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x
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@result{} normal-binding
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(a-cont #f)
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;; Prints:
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special-binding
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;; Evaluates to:
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@result{} a-cont ;; the value of the (define a-cont...)
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x
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@result{} normal-binding
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a-cont
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@result{} special-binding
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@end lisp"
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(@dynamic-wind in (thunk) out))
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;;;; Basic Port Code
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;;; Specifically, the parts of the low-level port code that are written in
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;;; Scheme rather than C.
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;;;
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;;; WARNING: the parts of this interface that refer to file ports
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;;; are going away. It would be gone already except that it is used
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;;; "internally" in a few places.
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;;; OPEN_READ, OPEN_WRITE, and OPEN_BOTH are used to request the
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;;; proper mode to open files in.
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;;;
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;;; If we want to support systems that do CRLF->LF translation, like
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;;; Windows, then we should have a symbol in scmconfig.h made visible
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;;; to the Scheme level that we can test here, and autoconf magic to
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;;; #define it when appropriate. Windows will probably just have a
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;;; hand-generated scmconfig.h file.
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(define OPEN_READ "r")
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(define OPEN_WRITE "w")
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(define OPEN_BOTH "r+")
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(define *null-device* "/dev/null")
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(define (open-input-file str)
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"Takes a string naming an existing file and returns an input port
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capable of delivering characters from the file. If the file
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cannot be opened, an error is signalled."
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(open-file str OPEN_READ))
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(define (open-output-file str)
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"Takes a string naming an output file to be created and returns an
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output port capable of writing characters to a new file by that
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name. If the file cannot be opened, an error is signalled. If a
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file with the given name already exists, the effect is unspecified."
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(open-file str OPEN_WRITE))
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(define (open-io-file str)
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"Open file with name STR for both input and output."
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(open-file str OPEN_BOTH))
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(define (call-with-input-file str proc)
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"PROC should be a procedure of one argument, and STR should be a
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string naming a file. The file must
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already exist. These procedures call PROC
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with one argument: the port obtained by opening the named file for
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input or output. If the file cannot be opened, an error is
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signalled. If the procedure returns, then the port is closed
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automatically and the values yielded by the procedure are returned.
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If the procedure does not return, then the port will not be closed
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automatically unless it is possible to prove that the port will
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never again be used for a read or write operation."
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(let ((p (open-input-file str)))
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(call-with-values
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(lambda () (proc p))
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(lambda vals
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(close-input-port p)
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(apply values vals)))))
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(define (call-with-output-file str proc)
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"PROC should be a procedure of one argument, and STR should be a
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string naming a file. The behaviour is unspecified if the file
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already exists. These procedures call PROC
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with one argument: the port obtained by opening the named file for
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input or output. If the file cannot be opened, an error is
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signalled. If the procedure returns, then the port is closed
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automatically and the values yielded by the procedure are returned.
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If the procedure does not return, then the port will not be closed
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automatically unless it is possible to prove that the port will
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never again be used for a read or write operation."
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(let ((p (open-output-file str)))
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(call-with-values
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(lambda () (proc p))
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(lambda vals
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(close-output-port p)
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(apply values vals)))))
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(define (with-input-from-port port thunk)
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(let* ((swaports (lambda () (set! port (set-current-input-port port)))))
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(dynamic-wind swaports thunk swaports)))
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(define (with-output-to-port port thunk)
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(let* ((swaports (lambda () (set! port (set-current-output-port port)))))
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(dynamic-wind swaports thunk swaports)))
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(define (with-error-to-port port thunk)
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(let* ((swaports (lambda () (set! port (set-current-error-port port)))))
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(dynamic-wind swaports thunk swaports)))
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(define (with-input-from-file file thunk)
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"THUNK must be a procedure of no arguments, and FILE must be a
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string naming a file. The file must already exist. The file is opened for
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input, an input port connected to it is made
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the default value returned by `current-input-port',
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and the THUNK is called with no arguments.
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When the THUNK returns, the port is closed and the previous
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default is restored. Returns the values yielded by THUNK. If an
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escape procedure is used to escape from the continuation of these
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procedures, their behavior is implementation dependent."
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(call-with-input-file file
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(lambda (p) (with-input-from-port p thunk))))
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(define (with-output-to-file file thunk)
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"THUNK must be a procedure of no arguments, and FILE must be a
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string naming a file. The effect is unspecified if the file already exists.
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The file is opened for output, an output port connected to it is made
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the default value returned by `current-output-port',
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and the THUNK is called with no arguments.
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When the THUNK returns, the port is closed and the previous
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default is restored. Returns the values yielded by THUNK. If an
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escape procedure is used to escape from the continuation of these
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procedures, their behavior is implementation dependent."
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(call-with-output-file file
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(lambda (p) (with-output-to-port p thunk))))
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(define (with-error-to-file file thunk)
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"THUNK must be a procedure of no arguments, and FILE must be a
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string naming a file. The effect is unspecified if the file already exists.
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The file is opened for output, an output port connected to it is made
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the default value returned by `current-error-port',
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and the THUNK is called with no arguments.
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When the THUNK returns, the port is closed and the previous
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default is restored. Returns the values yielded by THUNK. If an
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escape procedure is used to escape from the continuation of these
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procedures, their behavior is implementation dependent."
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(call-with-output-file file
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(lambda (p) (with-error-to-port p thunk))))
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(define (with-input-from-string string thunk)
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"THUNK must be a procedure of no arguments.
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The test of STRING is opened for
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input, an input port connected to it is made,
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and the THUNK is called with no arguments.
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When the THUNK returns, the port is closed.
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Returns the values yielded by THUNK. If an
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escape procedure is used to escape from the continuation of these
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procedures, their behavior is implementation dependent."
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(call-with-input-string string
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(lambda (p) (with-input-from-port p thunk))))
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(define (with-output-to-string thunk)
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"Calls THUNK and returns its output as a string."
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(call-with-output-string
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(lambda (p) (with-output-to-port p thunk))))
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(define (with-error-to-string thunk)
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"Calls THUNK and returns its error output as a string."
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(call-with-output-string
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(lambda (p) (with-error-to-port p thunk))))
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(define the-eof-object (call-with-input-string "" (lambda (p) (read-char p))))
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