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Program for Lexical Analysis

+2 votes
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Need a C program which reads a program written in any programming language and then
perform lexical analysis. The output of program should contain the tokens i.e. classification
as identifier, special symbol, delimiter, operator, keyword or string. It should also display the
number of identifiers, special symbol, delimiter, operator, keyword, strings and statements.

posted Feb 21, 2014 by Neeraj Pandey

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It is not possible to write a generic C program which can do lexical analysis of program written in any programming language since every language has different programming language constructs and correspondingly different leximes and different tokens................
Hmm one thing u can do..........
U can write different function for each programming language..........i mean to say different lexical analyser function for different program written in different language.(Hmmm some part may be sharable like identifying identifiers etc.)
U must have pre-awareness of the language of the program and accordingly u can invoke the function which does the lexical analysis of that program.

1 Answer

0 votes

Source : http://c-madeeasy.blogspot.in/2012/05/program-for-lexical-analyser-for-c.html

letter [a-zA-Z]  
 digit[0-9]  
 %%  
 {digit}+("E"("+"|"-")?{digit}+)? printf("\n%s\tis real number",yytext);  
 {digit}+"."{digit}+("E"("+"|"-")?{digit}+)? printf("\n%s\t is floating pt no ",yytext);  
 "if"|"else"|"int"|"char"|"scanf"|"printf"|"switch"|"return"|"struct"|"do"|"while"|"void"|"for"|"float" printf("\n%s\t is keywords",yytext);  
 "\a"|"\\n"|"\\b"|"\t"|"\\t"|"\b"|"\\a" printf("\n%s\tis Escape sequences",yytext);  
 {letter}({letter}|{digit})* printf("\n%s\tis identifier",yytext);  
 "&&"|"<"|">"|"<="|">="|"="|"+"|"-"|"?"|"*"|"/"|"%"|"&"|"||" printf("\n%s\toperator ",yytext);  
 "{"|"}"|"["|"]"|"("|")"|"#"|"'"|"."|"\""|"\\"|";"|"," printf("\n%s\t is a special character",yytext);  
 "%d"|"%s"|"%c"|"%f"|"%e" printf("\n%s\tis a format specifier",yytext);  
 %%  
 int yywrap()  
 {  
 return 1;  
 }  
 int main(int argc,char *argv[])  
 {  
 yyin=fopen(argv[1],"r");  
 yylex();  
 fclose(yyin);  
 return 0;  
 }  
 /*INPUT PROGRAM  
 #include<stdio.h>  
 void main()  
 {  
  printf("\nhai\n");  
 }  
/*
OUTPUT

#  is a special character
include is identifier
< operator 
stdio is identifier
.  is a special character
h is identifier
> operator 

void  is keywords 
main is identifier
(  is a special character
)  is a special character

{  is a special character

printf  is keywords
(  is a special character
"  is a special character
\n is Escape sequences
hai is identifier
\n is Escape sequences
"  is a special character
)  is a special character
;  is a special character

}  is a special character
*/
answer Mar 18, 2014 by Pavan P Naik
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