:: Re: [DNG] Studying C as told. (For …
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Autore: Rainer Weikusat
Data:  
To: dng
Oggetto: Re: [DNG] Studying C as told. (For help)
Edward Bartolo <edbarx@???> writes:
> I am saving your program for future study as its level is beyond the
> current level I am at. I am still at page 34 ("The C programming
> language" (Kernighan & Ritchie))


This is based on another simple idea, namely, instead of using a simple
pattern-recognition automaton, upon encountering a ' ', use a second
loop to skip over all immediately adjacent blanks. I thought about
providing an example of that but decided against it because I considered
it needlessly using a structurally unpleasant algorithm. An more
straight-forward example of this could be:

-----------
#include <stdio.h>

int main(void)
{
    int c;


    while ((c = getchar()) != EOF) {
    putchar(c);


    if (c == ' ') {
        do c = getchar(); while (c == ' ');
        if (c != EOF) putchar(c);
    }
    }


    return 0;
}
-----------


It's not necessary to break out of the outer loop upon encountering an
EOF in the inner one as the next getchar will again return EOF. Somewhat
interesting variant:

-----------
#include <stdio.h>

int main(void)
{
    int c;


    while ((c = getchar()) != EOF) {
    putchar(c);


    if (c == ' ') {
        do c = getchar(); while (c == ' ');
        if (c != EOF) ungetc(c, stdin);
    }
    }


    return 0;
}
----------


This uses ungetc to stuff the character which caused the inner loop to
terminate back into the stream so that the outer loop will read it again
next.