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;;; GNU Guix --- Functional package management for GNU
;;; Copyright © 2018, 2019 Ludovic Courtès <ludo@gnu.org>
;;;
;;; This file is part of GNU Guix.
;;;
;;; GNU Guix is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; GNU Guix 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 GNU Guix. If not, see <http://www.gnu.org/licenses/>.
(define-module (guix repl)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 match)
#:export (send-repl-response
machine-repl))
;;; Commentary:
;;;
;;; This module implements the "machine-readable" REPL provided by
;;; 'guix repl -t machine'. It's a lightweight module meant to be
;;; embedded in any Guile process providing REPL functionality.
;;;
;;; Code:
(define (self-quoting? x)
"Return #t if X is self-quoting."
(letrec-syntax ((one-of (syntax-rules ()
((_) #f)
((_ pred rest ...)
(or (pred x)
(one-of rest ...))))))
(one-of symbol? string? pair? null? vector?
bytevector? number? boolean?)))
(define (send-repl-response exp output)
"Write the response corresponding to the evaluation of EXP to PORT, an
output port."
(define (value->sexp value)
(if (self-quoting? value)
`(value ,value)
`(non-self-quoting ,(object-address value)
,(object->string value))))
(catch #t
(lambda ()
(let ((results (call-with-values
(lambda ()
(primitive-eval exp))
list)))
(write `(values ,@(map value->sexp results))
output)
(newline output)
(force-output output)))
(lambda (key . args)
(write `(exception ,key ,@(map value->sexp args)))
(newline output)
(force-output output))))
(define* (machine-repl #:optional
(input (current-input-port))
(output (current-output-port)))
"Run a machine-usable REPL over ports INPUT and OUTPUT.
The protocol of this REPL is meant to be machine-readable and provides proper
support to represent multiple-value returns, exceptions, objects that lack a
read syntax, and so on. As such it is more convenient and robust than parsing
Guile's REPL prompt."
(write `(repl-version 0 0) output)
(newline output)
(force-output output)
(let loop ()
(match (read input)
((? eof-object?) #t)
(exp
(send-repl-response exp output)
(loop)))))
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