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;;; Hoot REPL example
;;; Copyright (C) 2025 David Thompson <dave@spritely.institute>
;;;
;;; Licensed under the Apache License, Version 2.0 (the "License");
;;; you may not use this file except in compliance with the License.
;;; You may obtain a copy of the License at
;;;
;;; http://www.apache.org/licenses/LICENSE-2.0
;;;
;;; Unless required by applicable law or agreed to in writing, software
;;; distributed under the License is distributed on an "AS IS" BASIS,
;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;;; See the License for the specific language governing permissions and
;;; limitations under the License.
;;; Commentary:
;;;
;;; A barebones REPL to demonstrate how to use the interpreter. Input
;;; handling is *very* simplistic; far from a readline quality
;;; experience.
;;;
;;; Code:
(use-modules (fibers promises)
(fibers streams)
(hoot error-handling)
(hoot control)
(hoot eval)
(hoot exceptions)
(hoot interaction-environment)
(ice-9 match))
(define env (interaction-environment))
(define (run-repl in out)
(define (call-with-error-handling thunk)
(define tag (make-prompt-tag))
(call-with-prompt
tag
(lambda ()
;; This 5 number is determined empirically to trim the frames
;; within `with-exception-handler`. Terrible!
(define outer (+ (stack-height) 5))
(with-exception-handler
(lambda (exn)
;; Same, this 2 number is an empirical fudge. Woooo
(define stack (capture-stack (stack-height)))
(define inner (max (- (vector-length stack) 2) 0))
(define trimmed (vector-copy stack (min outer inner) inner))
(define port (current-error-port))
(define origin
(and (exception-with-origin? exn) (exception-origin exn)))
(call-with-values (lambda ()
(if (exception-with-source? exn)
(values (exception-source-file exn)
(exception-source-line exn)
(exception-source-column exn))
(values #f #f #f)))
(lambda (file line column)
(print-backtrace trimmed origin file line column port port)
(display "\nUncaught exception:\n" port)
(format-exception exn port)
(newline port)
(force-output port)
(abort-to-prompt tag))))
thunk
#:unwind? #f))
(lambda (k)
(values))))
(define (display-prompt)
(newline out)
(display "> " out)
(force-output out))
(define (eval* exp)
(call-with-error-handling
(lambda ()
(eval exp env))))
(define (print . vals)
(for-each (match-lambda
((? unspecified?)
(values))
(val
(newline out)
(display "=> " out)
(display val out)))
vals))
(display "Welcome to the Hoot REPL!\n\n" out)
(display "Press Ctrl-D to quit.\n" out)
(let loop ()
(display-prompt)
(match (peek-char in)
((? eof-object?)
(values))
(_
(let ((exp (read in)))
(call-with-values (lambda () (eval* exp)) print)
(loop))))))
(lambda (resolved rejected)
(call-with-async-result
resolved rejected
(lambda ()
(parameterize ((current-input-port (standard-input-stream))
(current-output-port (standard-output-stream)))
(run-repl (current-input-port) (current-output-port))))))
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