1 / 4

LEX

LEX. Input file: -31 4 54 6 -4 -665 Output file: -31 +4 +54 +6 -4 -665 Total=-636. %{ int total = 0; %} %% [0-9]+ { printf ( &quot; + &quot; ); REJECT;} [+/-]?[0-9]+ {ECHO; total+=atoi ( yytext ); } [ t<br>] {ECHO;} %% int yywrap ( void ) { printf (” Total=%d ”, total ); return 1;

bran
Download Presentation

LEX

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. LEX Input file: -31 4 54 6 -4 -665 Output file: -31 +4 +54 +6 -4 -665 Total=-636 %{ inttotal = 0; %} %% [0-9]+ {printf("+"); REJECT;} [+/-]?[0-9]+ {ECHO; total+=atoi(yytext);} [\ \t\n] {ECHO;} %% intyywrap(void) { printf(”Total=%d”, total); return 1; }

  2. LEX – BEGIN MACRO & TWO STATES Answerthequestion (Y/N): Istheinputcharactersequenceproperlycreatedwithusinglanguagedescribed by regularexpressionanbn, where n>=0 Input file: aaabbb aabbb Output file: aaabbb Y Y aabbb N %{ int a; int b; int OK=1; %} %start aaa %start bbb %% ^a {a=1; BEGIN aaa; ECHO;} <aaa>a {a++; ECHO;} <aaa>b {b=1; BEGIN bbb; ECHO;} <bbb>b {b++; ECHO;} \n {if (OK && a==b) printf(" Y\n"); else printf(" N\n"); a=0; b=0; OK=1;} . {OK=0; ECHO;}

  3. LEX & YACC Ourtaskis to computetotal sum of onlyodddigitsfrominput Input file: 017891 Output file: Total: 18 YACC code: %{ inttot = 0; %} %token oe %start X %% X: A {printf("Total: %d\n", tot);} | A error {yyerror();} ; A: A o{tot += yylval;} | A e | ; %% intyyerror() { printf("Syntax Error!!!\n"); exit(-1); } LEX code: %{ #include "ytab.h" %} %% [02468] {yylval=atoi(yytext);return e;} [13579] {yylval=atoi(yytext);return o;} \n ; . {YY_FATAL("Unexpected character!!!");}

More Related