;;; Read-Eval-Print Loop ;; Copyright (C) 2001, 2009, 2010, 2011, 2013, ;; 2014 Free Software Foundation, Inc. ;; This library is free software; you can redistribute it and/or ;; modify it under the terms of the GNU Lesser General Public ;; License as published by the Free Software Foundation; either ;; version 3 of the License, or (at your option) any later version. ;; ;; This library 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 ;; Lesser General Public License for more details. ;; ;; You should have received a copy of the GNU Lesser General Public ;; License along with this library; if not, write to the Free Software ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA ;; 02110-1301 USA ;;; Code: (define-module (system repl repl) #:use-module (system base language) #:use-module (system repl error-handling) #:use-module (system repl common) #:use-module (system repl command) #:use-module (ice-9 control) #:export (start-repl run-repl)) ;;; ;;; Comments ;;; ;;; (You don't want a comment to force a continuation line.) ;;; (define (read-scheme-line-comment port) (let lp () (let ((ch (read-char port))) (or (eof-object? ch) (eqv? ch #\newline) (lp))))) (define (read-scheme-datum-comment port) (read port)) ;; ch is a peeked char (define (read-comment lang port ch) (and (eq? (language-name lang) 'scheme) (case ch ((#\;) (read-char port) (read-scheme-line-comment port) #t) ((#\#) (read-char port) (case (peek-char port) ((#\;) (read-char port) (read-scheme-datum-comment port) #t) ;; Not doing R6RS block comments because of the possibility ;; of read-hash extensions. Lame excuse. Not doing scsh ;; block comments either, because I don't feel like handling ;; #!r6rs. (else (unread-char #\# port) #f))) (else #f)))) ;;; ;;; Meta commands ;;; (define meta-command-token (cons 'meta 'command)) (define (meta-reader lang env) (lambda* (#:optional (port (current-input-port))) (with-input-from-port port (lambda () (let ((ch (flush-leading-whitespace))) (cond ((eof-object? ch) (read-char)) ; consume the EOF and return it ((eqv? ch #\,) (read-char) meta-command-token) ((read-comment lang port ch) *unspecified*) (else ((language-reader lang) port env)))))))) (define (flush-all-input) (if (and (char-ready?) (not (eof-object? (peek-char)))) (begin (read-char) (flush-all-input)))) ;; repl-reader is a function defined in boot-9.scm, and is replaced by ;; something else if readline has been activated. much of this hoopla is ;; to be able to re-use the existing readline machinery. ;; ;; Catches read errors, returning *unspecified* in that case. ;; ;; Note: although not exported, this is used by (system repl coop-server) (define (prompting-meta-read repl) (catch #t (lambda () (repl-reader (lambda () (repl-prompt repl)) (meta-reader (repl-language repl) (current-module)))) (lambda (key . args) (case key ((quit) (apply throw key args)) (else (format (current-output-port) "While reading expression:\n") (print-exception (current-output-port) #f key args) (flush-all-input) *unspecified*))))) ;;; ;;; The repl ;;; (define* (start-repl #:optional (lang (current-language)) #:key debug) (start-repl* lang debug prompting-meta-read)) ;; Note: although not exported, this is used by (system repl coop-server) (define (start-repl* lang debug prompting-meta-read) ;; ,language at the REPL will update the current-language. Make ;; sure that it does so in a new dynamic scope. (parameterize ((current-language lang)) (run-repl* (make-repl lang debug) prompting-meta-read))) ;; (put 'abort-on-error 'scheme-indent-function 1) (define-syntax-rule (abort-on-error string exp) (catch #t (lambda () exp) (lambda (key . args) (format #t "While ~A:~%" string) (print-exception (current-output-port) #f key args) (abort)))) (define (run-repl repl) (run-repl* repl prompting-meta-read)) (define (run-repl* repl prompting-meta-read) (define (with-stack-and-prompt thunk) (call-with-prompt (default-prompt-tag) (lambda () (start-stack #t (thunk))) (lambda (k proc) (with-stack-and-prompt (lambda () (proc k)))))) (% (with-fluids ((*repl-stack* (cons repl (or (fluid-ref *repl-stack*) '())))) (if (null? (cdr (fluid-ref *repl-stack*))) (repl-welcome repl)) (let prompt-loop () (let ((exp (prompting-meta-read repl))) (cond ((eqv? exp *unspecified*)) ; read error or comment, pass ((eq? exp meta-command-token) (catch #t (lambda () (meta-command repl)) (lambda (k . args) (if (eq? k 'quit) (abort args) (begin (format #t "While executing meta-command:~%") (print-exception (current-output-port) #f k args)))))) ((eof-object? exp) (newline) (abort '())) (else ;; since the input port is line-buffered, consume up to the ;; newline (flush-to-newline) (call-with-error-handling (lambda () (catch 'quit (lambda () (call-with-values (lambda () (% (let ((thunk (abort-on-error "compiling expression" (repl-prepare-eval-thunk repl (abort-on-error "parsing expression" (repl-parse repl exp)))))) (run-hook before-eval-hook exp) (call-with-error-handling (lambda () (with-stack-and-prompt thunk)) #:on-error (repl-option-ref repl 'on-error))) (lambda (k) (values)))) (lambda l (for-each (lambda (v) (repl-print repl v)) l)))) (lambda (k . args) (abort args)))) #:on-error (repl-option-ref repl 'on-error) #:trap-handler 'disabled))) (flush-to-newline) ;; consume trailing whitespace (prompt-loop)))) (lambda (k status) status))) ;; Returns first non-whitespace char. (define (flush-leading-whitespace) (let ((ch (peek-char))) (cond ((eof-object? ch) ch) ((char-whitespace? ch) (read-char) (flush-leading-whitespace)) (else ch)))) (define (flush-to-newline) (if (char-ready?) (let ((ch (peek-char))) (if (and (not (eof-object? ch)) (char-whitespace? ch)) (begin (read-char) (if (not (char=? ch #\newline)) (flush-to-newline)))))))