mirror of https://github.com/ZDoom/gzdoom-gles.git
85 lines
3.2 KiB
ReasonML
85 lines
3.2 KiB
ReasonML
|
/* re2c lesson 001_upn_calculator, calc_001, (c) M. Boerger 2006 - 2007 */
|
||
|
|
/*!ignore:re2c
|
||
|
|
|
||
|
|
- basic interface for string reading
|
||
|
|
|
||
|
|
. We define the macros YYCTYPE, YYCURSOR, YYLIMIT, YYMARKER, YYFILL
|
||
|
|
. YYCTYPE is the type re2c operates on or in other words the type that
|
||
|
|
it generates code for. While it is not a big difference when we were
|
||
|
|
using 'unsigned char' here we would need to run re2c with option -w
|
||
|
|
to fully support types with sieof() > 1.
|
||
|
|
. YYCURSOR is used internally and holds the current scanner position. In
|
||
|
|
expression handlers, the code blocks after re2c expressions, this can be
|
||
|
|
used to identify the end of the token.
|
||
|
|
. YYMARKER is not always being used so we set an initial value to avoid
|
||
|
|
a compiler warning. Here we could also omit it compleley.
|
||
|
|
. YYLIMIT stores the end of the input. Unfortunatley we have to use strlen()
|
||
|
|
in this lesson. In the next example we see one way to get rid of it.
|
||
|
|
. We use a 'for(;;)'-loop around the scanner block. We could have used a
|
||
|
|
'while(1)'-loop instead but some compilers generate a warning for it.
|
||
|
|
. To make the output more readable we use 're2c:indent:top' scanner
|
||
|
|
configuration that configures re2c to prepend a single tab (the default)
|
||
|
|
to the beginning of each output line.
|
||
|
|
. The following lines are expressions and for each expression we output the
|
||
|
|
token name and continue the scanner loop.
|
||
|
|
. The second last token detects the end of our input, the terminating zero in
|
||
|
|
our input string. In other scanners detecting the end of input may vary.
|
||
|
|
For example binary code may contain \0 as valid input.
|
||
|
|
. The last expression accepts any input character. It tells re2c to accept
|
||
|
|
the opposit of the empty range. This includes numbers and our tokens but
|
||
|
|
as re2c goes from top to botton when evaluating the expressions this is no
|
||
|
|
problem.
|
||
|
|
. The first three rules show that re2c actually prioritizes the expressions
|
||
|
|
from top to bottom. Octal number require a starting "0" and the actual
|
||
|
|
number. Normal numbers start with a digit greater 0. And zero is finally a
|
||
|
|
special case. A single "0" is detected by the last rule of this set. And
|
||
|
|
valid ocal number is already being detected by the first rule. This even
|
||
|
|
includes multi "0" sequences that in octal notation also means zero.
|
||
|
|
Another way would be to only use two rules:
|
||
|
|
"0" [0-9]+
|
||
|
|
"0" | ( [1-9] [0-9]* )
|
||
|
|
A full description of re2c rule syntax can be found in the manual.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <stdio.h>
|
||
|
|
#include <string.h>
|
||
|
|
|
||
|
|
int scan(char *s, int l)
|
||
|
|
{
|
||
|
|
char *p = s;
|
||
|
|
char *q = 0;
|
||
|
|
#define YYCTYPE char
|
||
|
|
#define YYCURSOR p
|
||
|
|
#define YYLIMIT (s+l)
|
||
|
|
#define YYMARKER q
|
||
|
|
#define YYFILL(n)
|
||
|
|
|
||
|
|
for(;;)
|
||
|
|
{
|
||
|
|
/*!re2c
|
||
|
|
re2c:indent:top = 2;
|
||
|
|
"0"[0-9]+ { printf("Oct\n"); continue; }
|
||
|
|
[1-9][0-9]* { printf("Num\n"); continue; }
|
||
|
|
"0" { printf("Num\n"); continue; }
|
||
|
|
"+" { printf("+\n"); continue; }
|
||
|
|
"-" { printf("-\n"); continue; }
|
||
|
|
"\000" { printf("EOF\n"); return 0; }
|
||
|
|
[^] { printf("ERR\n"); return 1; }
|
||
|
|
*/
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
int main(int argc, char **argv)
|
||
|
|
{
|
||
|
|
if (argc > 1)
|
||
|
|
{
|
||
|
|
return scan(argv[1], strlen(argv[1]));
|
||
|
|
}
|
||
|
|
else
|
||
|
|
{
|
||
|
|
fprintf(stderr, "%s <expr>\n", argv[0]);
|
||
|
|
return 1;
|
||
|
|
}
|
||
|
|
}
|