ikarus/scheme/ikarus.cafe.ss

119 lines
4.0 KiB
Scheme

;;; Ikarus Scheme -- A compiler for R6RS Scheme.
;;; Copyright (C) 2006,2007 Abdulaziz Ghuloum
;;;
;;; This program is free software: you can redistribute it and/or modify
;;; it under the terms of the GNU General Public License version 3 as
;;; published by the Free Software Foundation.
;;;
;;; This program is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see <http://www.gnu.org/licenses/>.
#|procedure:new-cafe
synopsis:
(new-cafe [eval])
description:
The procedure new-cafe starts a new read-eval-print loop inside
the current cafe (if one exists). It prompts the user for an
expression, evaluates it, prints the result back, and repeats the
process. If new-cafe is called with an argument, eval, then that
argument must be a procedure that takes a single argument. The
eval procedure will be used to evaluate the expressions.
Every time a new cafe is started, the prompt is changed to reflect
the depth of the current cafe (i.e. how many eof objects is takes
to exit the outermost cafe).
Input and output performed by the cafe can be changed by the
console-input-port and console-output-port parameters.
If an error occurs during reading, evaluating, or printing an
expression, then the error is printed to the error-port and the
operations of the cafe resume as normal.|#
#|FIXME:new-cafe
Be specific about what the error-port is |#
(library (ikarus cafe)
(export new-cafe)
(import
(only (rnrs) with-exception-handler)
(only (psyntax expander) eval-top-level)
(except (ikarus) new-cafe))
(define eval-depth 0)
(define display-prompt
(lambda (i)
(if (fx= i eval-depth)
(display " " (console-output-port))
(begin
(display ">" (console-output-port))
(display-prompt (fx+ i 1))))))
(define my-read
(lambda (k)
(parameterize ([interrupt-handler
(lambda ()
(flush-output-port (console-output-port))
(reset-input-port! (console-input-port))
(newline (console-output-port))
(k))])
(read (console-input-port)))))
(define wait
(lambda (eval-proc escape-k)
(call/cc
(lambda (k)
(with-exception-handler
(lambda (con)
(reset-input-port! (console-input-port))
(flush-output-port (console-output-port))
(display "Unhandled exception\n")
(print-condition con)
(k (void)))
(lambda ()
(display-prompt 0)
(let ([x (my-read k)])
(cond
[(eof-object? x)
(newline (console-output-port))
(escape-k (void))]
[else
(call-with-values
(lambda () (eval-proc x))
(lambda v*
(unless (andmap (lambda (v) (eq? v (void))) v*)
(for-each
(lambda (v)
(pretty-print v (console-output-port)))
v*))))]))))))
(wait eval-proc escape-k)))
(define do-new-cafe
(lambda (eval-proc)
(dynamic-wind
(lambda () (set! eval-depth (fxadd1 eval-depth)))
(lambda ()
(call/cc
(lambda (k)
(wait eval-proc k))))
(lambda () (set! eval-depth (fxsub1 eval-depth))))))
(define default-cafe-eval
(lambda (x)
(eval-top-level x)))
(define new-cafe
(case-lambda
[() (do-new-cafe default-cafe-eval)]
[(p)
(unless (procedure? p)
(error 'new-cafe "not a procedure" p))
(do-new-cafe p)]))
)