exercise06.c

// C Primer Plus
// Chapter 11 Exercise 6:

// Write a function called is_within() that takes a character and a string
// pointer as its two function parameters. Have the function return a
// nonzero value (true) if the character is in the string and zero (false)
// otherwise. Test the function in a complete program that uses a loop to
// provide input values for feeding to the function.

#include <stdio.h>

#define LIMIT 50

int is_within(char ch, const char *string);
char * get(char *string, int n);

int main(void)
{
	// test is_within()

	char string[LIMIT];
	char ch;

	printf("Enter a string to search: ");
	get(string, LIMIT);
	while (string[0] != '\0')
	{
		printf("Enter a character to search for: ");
		ch = getchar();

		if (ch != '\n')
			while (getchar() != '\n')
				continue;

		char *contains = is_within(ch, string) ? "" : " not";

		printf("\"%s\" does%s contain %c\n", string, contains, ch);

		printf("Enter a string to search (empty line to quit): ");
		get(string, LIMIT);
	}
	puts("Bye");

	return 0;
}

int is_within(char ch, const char *string)
{
	// returns 1 if char ch is in string
	// returns 0 otherwise

	while(*string != '\0')
	{
		if (*string == ch)
			return 1;

		string++;
	}

	return 0;
}

char * get(char *string, int n)
{
	// wrapper for fgets that replaces first newline with null

	char *return_value = fgets(string, n, stdin);

	while (*string != '\0')
	{
		if (*string == '\n')
		{
			*string = '\0';
			break;
		}

		string++;
	}

	return return_value;
}