Lex program for Decimal to Binary Conversion

Problem: Write a Lex program for Decimal to Binary conversion.

Explanation:
FLEX (Fast Lexical Analyzer Generator) is a tool/computer program for generating lexical analyzers (scanners or lexers) written by Vern Paxson in C around 1987. Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language. The function yylex() is the main flex function which runs the Rule Section.

Examples:



Input: 12 
Output: 1100

Input: 115
Output: 1110011

Input: 25
Output: 11001

Input: 220
Output: 11011100 

Implementation:

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/* Lex program for decimal to binary conversion */
  
%{
  /* Definition section */
  #include<stdio.h>
  int num, r, b=0, p=1;
%}
  
DIGIT [0-9]
/* Rule Section */
%%
{DIGIT}+   { num=atoi(yytext);
             while (num > 0)
             {
              r= num % 2;
              b+= r*p;
              p*= 10;
              num/= 2;
             }
              printf("%d", b);
            }
.|\n    ECHO;
         
%%
  
// driver code 
int main()
{
    yylex();
    return 0;
}      

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Output:



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