The final step in my Pig Latin journey is to process an entire English language sentence. The piglatin() function, finished in last week’s Lesson, requires no updates. But chopping a sentence into words and sending them off to be processed individually proved to be an interesting exercise.

To parse words from a sentence, I process the input string from beginning to end. A while loop churns through each character. To find words in the sentence, an if test uses the isalapha() ctype function to check for letters of the alphabet, upper- or lowercase:

while(start-sentence<len)
{
    if( isalpha(*start) )

Pointer variable start is initialized to the input string’s address, sentence; len is the string’s length.

When the isalpha() test is true, pointer start references the start of a word. Pointer end is assigned the address stored in start. Then a nested while loop continues processing alphabetic characters to locate the end of the word, moving pointer end along the way:

end = start;
while( isalpha(*end) || *end=='\'' )
    end++;

The loop ends when a word is found. The non-alpha character after the word is saved in char variable save, then the word referenced by pointer start is capped:

save = *end;
*end = '\0';

The word is now parsed and can be processed by the piglatin() function:

printf("%s",piglatin(start));

After the Pig Latin translation is output, variable start is updated to look for another word. The non-alpha character saved in variable save is output to ensure consistency between the original and Pig Latin string:

start = end+1;
putchar(save);

Here is the full code:

2024_12_28-Lesson.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

/* test for vowels */
int isvowel(char a)
{
    if( a=='A' || a=='a' )
        return 1;
    if( a=='E' || a=='e' )
        return 1;
    if( a=='I' || a=='i' )
        return 1;
    if( a=='O' || a=='o' )
        return 1;
    if( a=='U' || a=='u' )
        return 1;
    return 0;
}

/* translate a word into piglatin */
char *piglatin(char *s)
{
    char *si,*pig;

    /* word starts with a vowel, add -hay */
    if( isvowel(*s) )
    {
        pig = malloc( strlen(s)+4+1 );    /* "-hay" + '\0' */
        if( pig==NULL )
            return("Memory Error");
        strcpy(pig,s);
        strcat(pig,"-hay");
    }
    else
    {
    /* move first consonant/consonant cluster
       add -ay */
        si = s;
        while( !isvowel(*si) )
        {
            si++;
            if( *si=='\0' )
                return("Invalid word");
        }
        pig = malloc( strlen(s)+3+1 );    /* "-ay" + '\0' */
        if( pig==NULL )
        return("Memory Error");
        strcpy(pig,si);
        strcpy(pig,"-");
        strncat(pig,s,si-s);
        strcat(pig,"ay");
    }

    return pig;
}

int main()
{
    char sentence[BUFSIZ];
    char *start,*end;
    char save;
    int len;

    printf("Original sentence: ");
    fgets(sentence,BUFSIZ,stdin);
    printf("Piglatin sentence: ");

    /* chop sentence into word chunks */
    start = sentence;
    len = strlen(sentence);
    while(start-sentence<len)
    {
        if( isalpha(*start) )
        {
            end = start;
            while( isalpha(*end) || *end=='\'' )
                end++;
            save = *end;
            *end = '\0';
            printf("%s",piglatin(start));
            start = end+1;
            putchar(save);
        }
        else
        {
            putchar(*start);
            start++;
        }
    }

    return 0;
}

The isvowel() and piglatin() functions are unchanged from last week’s code. The only modifications are in the main() function, as described earlier. Here is a sample run:

Original sentence: Greetings from Dan Gookin!
Piglatin sentence: eetings-Gray om-fray an-Day ookin-Gay!

I suppose another modification I could make would be to transform this code into a filter, as presented in my book C All-In-One Desk Reference For Dummies. But I’m weary of the whole Pig Latin thing, so I’ll save this task for a future Lesson.