Learn to Program with C_ Learn to Program using the Popular C Programming Language ( PDFDrive )

Chapter 8 ■ Arrays
Comments on the functionlettersOnlyLower
• i is used to index the given phrase, stored in phrase.
• n is used to index the converted phrase, stored in word.
• The while loop looks at each character of phrase, in turn. If it is a letter, it is
converted to lowercase using the predefined function tolower and stored in
the next position in word; to use tolower, your program must be preceded
by the directive
#include <ctype.h>
• On exit from the while, word is properly terminated with \0.
Putting everything together, we get Program P8.5, which tests our new function,
letterOnlyLower.
Program P8.5
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main() {
char aPhrase[100], aWord[100];
void lettersOnlyLower(char p[], char w[]);
int palindrome(char str[]);
printf("Type a phrase. (To stop, press 'Enter' only): ");
gets(aPhrase);
while (strcmp(aPhrase, "") != 0) {
lettersOnlyLower(aPhrase, aWord);
printf("Converted to: %s\n", aWord);
if (palindrome(aWord)) printf("is a palindrome\n");
else printf("is not a palindrome\n");
printf("Type a word. (To stop, press 'Enter' only): ");
gets(aPhrase);
} //end while
} //end main
void lettersOnlyLower(char phrase[], char word[]) {
int j = 0, n = 0;
char c;
while ((c = phrase[j++]) != '\0')
if (isalpha(c)) word[n++] = tolower(c);
word[n] = '\0';
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