/*
* read.c
*
* First pass at a reader, for bootstrapping.
*
*
* (c) 2017 Simon Brooke <simon@journeyman.cc>
* Licensed under GPL version 2.0, or, at your option, any later version.
*/
#include <math.h>
#include <stdbool.h>
#include <stdio.h>
/*
* wide characters
*/
#include <wchar.h>
#include <wctype.h>
#include "consspaceobject.h"
#include "debug.h"
#include "dump.h"
#include "integer.h"
#include "intern.h"
#include "lispops.h"
#include "peano.h"
#include "print.h"
#include "ratio.h"
#include "read.h"
#include "real.h"
#include "vectorspace.h"
/*
* for the time being things which may be read are: strings numbers - either
* integer or real, but not yet including ratios or bignums lists Can't read
* atoms because I don't yet know what an atom is or how it's stored.
*/
struct cons_pointer read_number( struct stack_frame *frame,
struct cons_pointer frame_pointer,
FILE * input, wint_t initial,
bool seen_period );
struct cons_pointer read_list( struct stack_frame *frame,
struct cons_pointer frame_pointer, FILE * input,
wint_t initial );
struct cons_pointer read_string( FILE * input, wint_t initial );
struct cons_pointer read_symbol( FILE * input, wint_t initial );
/**
* quote reader macro in C (!)
*/
struct cons_pointer c_quote( struct cons_pointer arg ) {
return make_cons( c_string_to_lisp_symbol( L"quote" ),
make_cons( arg, NIL ) );
}
/**
* Read the next object on this input stream and return a cons_pointer to it,
* treating this initial character as the first character of the object
* representation.
*/
struct cons_pointer read_continuation( struct stack_frame *frame,
struct cons_pointer frame_pointer,
FILE * input, wint_t initial ) {
debug_print( L"entering read_continuation\n", DEBUG_IO );
struct cons_pointer result = NIL;
wint_t c;
for ( c = initial;
c == '\0' || iswblank( c ) || iswcntrl( c ); c = fgetwc( input ) );
if ( feof( input ) ) {
result =
throw_exception( c_string_to_lisp_string
( L"End of file while reading" ), frame_pointer );
} else {
switch ( c ) {
case ';':
for ( c = fgetwc( input ); c != '\n'; c = fgetwc( input ) );
/* skip all characters from semi-colon to the end of the line */
break;
case EOF:
result = throw_exception( c_string_to_lisp_string
( L"End of input while reading" ),
frame_pointer );
break;
case '\'':
result =
c_quote( read_continuation
( frame, frame_pointer, input,
fgetwc( input ) ) );
break;
case '(':
result =
read_list( frame, frame_pointer, input, fgetwc( input ) );
break;
case '"':
result = read_string( input, fgetwc( input ) );
break;
case '-':{
wint_t next = fgetwc( input );
ungetwc( next, input );
if ( iswdigit( next ) ) {
result =
read_number( frame, frame_pointer, input, c,
false );
} else {
result = read_symbol( input, c );
}
}
break;
case '.':
{
wint_t next = fgetwc( input );
if ( iswdigit( next ) ) {
ungetwc( next, input );
result =
read_number( frame, frame_pointer, input, c,
true );
} else if ( iswblank( next ) ) {
/* dotted pair. TODO: this isn't right, we
* really need to backtrack up a level. */
result =
read_continuation( frame, frame_pointer, input,
fgetwc( input ) );
} else {
read_symbol( input, c );
}
}
break;
default:
if ( iswdigit( c ) ) {
result =
read_number( frame, frame_pointer, input, c, false );
} else if ( iswprint( c ) ) {
result = read_symbol( input, c );
} else {
result =
throw_exception( make_cons( c_string_to_lisp_string
( L"Unrecognised start of input character" ),
make_string( c, NIL ) ),
frame_pointer );
}
break;
}
}
debug_print( L"read_continuation returning\n", DEBUG_IO );
debug_dump_object( result, DEBUG_IO );
return result;
}
/**
* read a number from this input stream, given this initial character.
* TODO: Need to do a lot of inc_ref and dec_ref, to make sure the
* garbage is collected.
*/
struct cons_pointer read_number( struct stack_frame *frame,
struct cons_pointer frame_pointer,
FILE * input,
wint_t initial, bool seen_period ) {
debug_print( L"entering read_number\n", DEBUG_IO );
struct cons_pointer result = make_integer( 0, NIL );
/* TODO: we really need to be getting `base` from a privileged Lisp name -
* and it should be the same privileged name we use when writing numbers */
struct cons_pointer base = make_integer( 10, NIL );
struct cons_pointer dividend = NIL;
int places_of_decimals = 0;
wint_t c;
bool neg = initial == btowc( '-' );
if ( neg ) {
initial = fgetwc( input );
}
debug_printf( DEBUG_IO, L"read_number starting '%c' (%d)\n", initial,
initial );
for ( c = initial; iswdigit( c )
|| c == L'.' || c == L'/' || c == L','; c = fgetwc( input ) ) {
switch (c) {
case L'.':
if ( seen_period || !nilp( dividend ) ) {
return throw_exception( c_string_to_lisp_string
( L"Malformed number: too many periods" ),
frame_pointer );
} else {
debug_print(L"read_number: decimal point seen\n", DEBUG_IO);
seen_period = true;
}
break;
case L'/':
if ( seen_period || !nilp( dividend ) ) {
return throw_exception( c_string_to_lisp_string
( L"Malformed number: dividend of rational must be integer" ),
frame_pointer );
} else {
debug_print(L"read_number: ratio slash seen\n", DEBUG_IO);
dividend = result;
result = make_integer( 0, NIL );
}
break;
case L',' :
// silently ignore it.
break;
default:
result = add_integers( multiply_integers( result, base ),
make_integer( ( int ) c - ( int ) '0',
NIL ) );
debug_printf( DEBUG_IO,
L"read_number: added character %c, result now ", c );
debug_print_object( result, DEBUG_IO);
debug_print( L"\n", DEBUG_IO);
if ( seen_period ) {
places_of_decimals++;
}
}
}
/*
* push back the character read which was not a digit
*/
ungetwc( c, input );
if ( seen_period ) {
debug_print(L"read_number: converting result to real\n", DEBUG_IO);
struct cons_pointer div = make_ratio( frame_pointer, result,
make_integer( powl
( to_long_double
( base ),
places_of_decimals ),
NIL ) );
inc_ref( div );
result = make_real( to_long_double( div ) );
dec_ref( div );
} else if ( integerp( dividend ) ) {
debug_print(L"read_number: converting result to ratio\n", DEBUG_IO);
result = make_ratio( frame_pointer, dividend, result );
}
if ( neg ) {
debug_print(L"read_number: converting result to negative\n", DEBUG_IO);
result = negative( frame_pointer, result );
}
debug_print( L"read_number returning\n", DEBUG_IO );
debug_dump_object( result, DEBUG_IO );
return result;
}
/**
* Read a list from this input stream, which no longer contains the opening
* left parenthesis.
*/
struct cons_pointer read_list( struct stack_frame *frame,
struct cons_pointer frame_pointer,
FILE * input, wint_t initial ) {
struct cons_pointer result = NIL;
if ( initial != ')' ) {
debug_printf( DEBUG_IO,
L"read_list starting '%C' (%d)\n", initial, initial );
struct cons_pointer car =
read_continuation( frame, frame_pointer, input,
initial );
result =
make_cons( car,
read_list( frame, frame_pointer, input,
fgetwc( input ) ) );
} else {
debug_print( L"End of list detected\n", DEBUG_IO );
}
return result;
}
/**
* Read a string. This means either a string delimited by double quotes
* (is_quoted == true), in which case it may contain whitespace but may
* not contain a double quote character (unless escaped), or one not
* so delimited in which case it may not contain whitespace (unless escaped)
* but may contain a double quote character (probably not a good idea!)
*/
struct cons_pointer read_string( FILE * input, wint_t initial ) {
struct cons_pointer cdr = NIL;
struct cons_pointer result;
switch ( initial ) {
case '\0':
result = make_string( initial, NIL );
break;
case '"':
/* making a string of the null character means we can have an empty
* string. Just returning NIL here would make an empty string
* impossible. */
result = make_string( '\0', NIL );
break;
default:
result =
make_string( initial, read_string( input, fgetwc( input ) ) );
break;
}
return result;
}
struct cons_pointer read_symbol( FILE * input, wint_t initial ) {
struct cons_pointer cdr = NIL;
struct cons_pointer result;
switch ( initial ) {
case '\0':
result = make_symbol( initial, NIL );
break;
case '"':
/*
* THIS IS NOT A GOOD IDEA, but is legal
*/
result =
make_symbol( initial, read_symbol( input, fgetwc( input ) ) );
break;
case ')':
/*
* symbols may not include right-parenthesis
*/
result = NIL;
/*
* push back the character read
*/
ungetwc( initial, input );
break;
default:
if ( iswprint( initial )
&& !iswblank( initial ) ) {
result =
make_symbol( initial,
read_symbol( input, fgetwc( input ) ) );
} else {
result = NIL;
/*
* push back the character read
*/
ungetwc( initial, input );
}
break;
}
debug_print( L"read_symbol returning\n", DEBUG_IO );
debug_dump_object( result, DEBUG_IO );
return result;
}
/**
* Read the next object on this input stream and return a cons_pointer to it.
*/
struct cons_pointer read( struct
stack_frame
*frame, struct cons_pointer frame_pointer,
FILE * input ) {
return read_continuation( frame, frame_pointer, input, fgetwc( input ) );
}