Lex program to check perfect numbers
Lex is a computer program that generates lexical analyzers and was written by Mike Lesk and Eric Schmidt. Lex reads an input stream specifying the lexical analyzer and outputs source code implementing the lexer in the C programming language.
Description: Perfect number, a positive integer that is equal to the sum of its proper divisors, for example: 6 = 1+2+3.
Examples:
Input: 3 Output: 3 is not perfect number Input: 6 Output: 6 is perfect number
Implementation:
/*Lex program to check perfect numbers*/ %{#include <string.h> void check(char*); %} /*Rule Section*/% % [0 - 9] + check(yytext);% % int main(){ // the input stream pointer extern FILE* yyin; // open a file handle to a particular file yyin = fopen("num", "r"); // The function that starts the analysis yylex(); return 0;}void check(char* a){ int len = strlen(a), i, num = 0; for (i = 0; i < len; i++) num = num * 10 + (a[i] - '0'); int x = 0, temp = num; for (i = 1; i < num; i++) { if (num % i == 0) x = x + i; } if (x == temp) printf("%d is perfect number \n", num); else printf("%d is not perfect number \n", num);} |
Output:
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