Intel XENIX 286 Programmers Guide (86) - Tenox.tc

XENIX Programming
I* lexical analysis *I
yylex(){
register c;
{I* skip over blanks *I }
while( ( c = getchar( )) = = ' ' )
if ( isupper(c) ){
yylval.ival = c-'A';
return( VREG );
}
if ( islower(c) ){
yylval.ival = c -'a';
return( DREG );
}
if( isdigit( c) II c = = '.' ){
I* gobble up digits, points, exponents *I
char buf[BSZ + 1], * cp = buf;
int dot = 0, exp = 0;
for( ; (cp-buf) < BSZ ; + + cp,c = getchar() ){
*cp = c;
if ( isdigit(c) ) continue;
if(c =='.' ){
if( dot + + ll exp ) return( '.' );
I* above causes syntax error *I
continue;
}
if (c = = 'e' ) {
if ( exp + + ) return( ' e' );
I* above causes syntax error *I
continue;
}
I* end of number *I
break;
}
*cp = '\eO';
if( (cp-buf) > = BSZ )
printf( "constant too long: truncated\n");
else ungetc( c, stdin );
I* above pushes back last char read *I
yylval.dval = atof { buf );
return{ CONST );
}
return{ c);
}
yacc: Compiler-Compiler
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