commonly used idioms

i only know a few common idioms.
how many commonly used idioms are there in c.
these are the ones i can think of right now.

Code:

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while((c=getchar()) != EOF        )

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Code:

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for(i=1;i < argc;i++)
    if((fp=fopen(argc[i],"r"))==NULL)

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Code:

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for(;;)
  /*endless*/

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Code:

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while(1)
{
/*endless*/
}

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Quote:

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how many commonly used idioms are there in c.

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There's hundreds, possibly thousands. Certainly more than can be mentioned here.

Also, I don't see how attempting to open every passed command-line argument is a commonly used idiom.

I always write stuff like that on-the-fly

Code:

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if (!(lf = fopen(LOGFILE_NAME, "a"))) {
    printf("Failure to create or open logfile: %s\n", LOGFILE_NAME);

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or this little gem:

Code:

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void insert_commas(char *inp, char *outp) {
int a = (21 - (int)strlen(inp)) % 3, d;
for (; outp[ d = a / 3] = *inp++; a += 4)
        outp[d + 1] = ',';
outp[d - 1] = '\0'; }

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Not sure if I'd classify them as idioms. Maybe they're just convoluted examples of terseness.

Code:

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for(p = head; p; p = p->next) ...

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for-loop walking through a linked list.

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Mats

reason i asked is that i read this book The Practice of Programming - Google Bøger

and there is lots of examples of idioms but the book is getting a bit old. i bought the book second hand and i read it a while ago. that one and the book the unix programming environment along with the c programming language is the books i learn from and try to adapt as much as i can from those.

Quote:

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Originally Posted by cmay

and there is lots of examples of idioms but the book is getting a bit old.

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I'm going to go out on a limb and say that all useful idioms in C have already been discovered. The age of the book isn't really important.

To be an idiom, a code construct has to be:

* An implementation of a specific, low-level behavior which could feasibly be accomplished in an alternative way
* Widely deployed
* Immediately recognized and understood by any experienced programmer

The first criterion is what separates an idiom from a design pattern.

Idioms are old, that's why they're called idioms :)
That is, everybody uses them, and they recognise them when they see them.

I'd like to see some examples from the book... I really can't think of any that couldn't be generated on-the-fly when needed. There couldn't be anything super cool there, I figure. I doubt C is a complex & dense enough language that one needs a library of idioms anyhow.