turtle.lex

%top{
#include <string.h>
#include <stdlib.h>
#include <glib.h>
#include "turtle_parser.h"

  static int nline = 1;
  static int ncolumn = 1;
  static void get_location (char *text);

  /* Dinamically allocated memories are added to the single list. They will be freed in the finalize function. */
  extern GSList *list;
}

%option noyywrap

REAL_NUMBER (0|[1-9][0-9]*)(\.[0-9]+)?
IDENTIFIER [a-zA-Z][a-zA-Z0-9]*
%%
  /* rules */
#.*               ; /* comment. Be careful. Dot symbol (.) matches any character but new line. */
[ ]               ncolumn++; /* white space. [ and ] is a "character class". */
\t                ncolumn += 8; /* assume that tab is 8 spaces. */
\n                nline++; ncolumn = 1;
  /* reserved keywords */
pu                get_location (yytext); return PU; /* pen up */
pd                get_location (yytext); return PD; /* pen down */
pw                get_location (yytext); return PW; /* pen width = line width */
fd                get_location (yytext); return FD; /* forward */
tr                get_location (yytext); return TR; /* turn right */
tl                get_location (yytext); return TL; /* turn left, since ver 0.5 */
bc                get_location (yytext); return BC; /* background color */
fc                get_location (yytext); return FC; /* foreground color */
dp                get_location (yytext); return DP; /* define procedure */
if                get_location (yytext); return IF; /* if statement */
rt                get_location (yytext); return RT; /* return statement */
rs                get_location (yytext); return RS; /* reset the status */
rp                get_location (yytext); return RP; /* repeat, since ver 0.5 */
  /* constant */
{REAL_NUMBER}     get_location (yytext); yylval.NUM = atof (yytext); return NUM;
  /* identifier */
{IDENTIFIER}      { get_location (yytext); yylval.ID = g_strdup(yytext);
                    list = g_slist_prepend (list, yylval.ID);
                    return ID;
                  }
"="               get_location (yytext); return '=';
">"               get_location (yytext); return '>';
"<"               get_location (yytext); return '<';
"+"               get_location (yytext); return '+';
"-"               get_location (yytext); return '-';
"*"               get_location (yytext); return '*';
"/"               get_location (yytext); return '/';
"("               get_location (yytext); return '(';
")"               get_location (yytext); return ')';
"{"               get_location (yytext); return '{';
"}"               get_location (yytext); return '}';
","               get_location (yytext); return ',';
.                 ncolumn++;             return YYUNDEF;
%%

static void
get_location (char *text) {
  yylloc.first_line = yylloc.last_line = nline;
  yylloc.first_column = ncolumn;
  yylloc.last_column = (ncolumn += strlen(text)) - 1;
}

static YY_BUFFER_STATE state;

void
init_flex (const char *text) {
  state = yy_scan_string (text);
}

void
finalize_flex (void) {
  yy_delete_buffer (state);
}