98 lines
2.6 KiB
C
98 lines
2.6 KiB
C
/*
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* repl.c
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*
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* the read/eval/print loop
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*
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* (c) 2017 Simon Brooke <simon@journeyman.cc>
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* Licensed under GPL version 2.0, or, at your option, any later version.
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*/
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#include <stdbool.h>
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#include <stdio.h>
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#include <wchar.h>
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#include "conspage.h"
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#include "consspaceobject.h"
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#include "intern.h"
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#include "lispops.h"
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#include "read.h"
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#include "print.h"
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#include "stack.h"
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/* TODO: this is subtly wrong. If we were evaluating
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* (print (eval (read)))
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* then the stack frame for read would have the stack frame for
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* eval as parent, and it in turn would have the stack frame for
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* print as parent.
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*/
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/**
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* Dummy up a Lisp read call with its own stack frame.
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*/
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struct cons_pointer repl_read( struct cons_pointer stream_pointer ) {
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struct stack_frame *frame = make_empty_frame( NULL, oblist );
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frame->arg[0] = stream_pointer;
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struct cons_pointer result = lisp_read( frame, oblist );
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free_stack_frame( frame );
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return result;
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}
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/**
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* Dummy up a Lisp eval call with its own stack frame.
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*/
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struct cons_pointer repl_eval( struct cons_pointer input ) {
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struct stack_frame *frame = make_empty_frame( NULL, oblist );
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frame->arg[0] = input;
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struct cons_pointer result = lisp_eval( frame, oblist );
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free_stack_frame( frame );
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return result;
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}
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/**
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* Dummy up a Lisp print call with its own stack frame.
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*/
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struct cons_pointer repl_print( struct cons_pointer stream_pointer,
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struct cons_pointer value ) {
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struct stack_frame *frame = make_empty_frame( NULL, oblist );
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frame->arg[0] = value;
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frame->arg[1] = NIL /* stream_pointer */ ;
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struct cons_pointer result = lisp_print( frame, oblist );
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free_stack_frame( frame );
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return result;
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}
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/**
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* The read/eval/print loop
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* @param in_stream the stream to read from;
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* @param out_stream the stream to write to;
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* @param err_stream the stream to send errors to;
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* @param show_prompt true if prompts should be shown.
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*/
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void
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repl( FILE * in_stream, FILE * out_stream, FILE * error_stream,
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bool show_prompt ) {
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struct cons_pointer input_stream = make_read_stream( in_stream );
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struct cons_pointer output_stream = make_write_stream( out_stream );
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while ( !feof( pointer2cell( input_stream ).payload.stream.stream ) ) {
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if ( show_prompt ) {
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fwprintf( out_stream, L"\n:: " );
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}
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struct cons_pointer val = repl_eval( repl_read( input_stream ) );
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/* suppress the 'end of stream' exception */
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if ( !exceptionp( val ) &&
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!feof( pointer2cell( input_stream ).payload.stream.stream ) ) {
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repl_print( output_stream, val );
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}
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}
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}
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