Lex Program to accept string starting with vowel

Lex Program to accept string starting with vowel

Last Updated : 30 Sep, 2022

Lex is a computer program that generates lexical analyzers. Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language. The commands for executing the lex program are:

lex abc.l (abc is the file name)
cc lex.yy.c -efl
./a.out

Let’s see lex program to accept string starting with vowel. Examples:

Input: animal
Output: Accepted

Input: zebra
Output: Not Accepted

Below is the implementation:

C

/* Lex Program to accept string starting with vowel */
% {
  int flag = 0;
% }

%%

[aeiouAEIOU].[a-zA-Z0-9.]+ flag=1;
[a-zA-Z0-9]+

%%

main()
{
 yylex();
 if (flag == 1) 
    printf("Accepted"); 
 else
    printf("Not Accepted"); 
}

Output:

Lex Program to accept string starting with vowel

T

Tanmay_Jain

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