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Synlar
Synlar

Reputation: 101

C - Why must NULL be compared to?

I'm curious as to why when say I traverse a linked list iteratively I must do while (list != NULL) instead of while (!list). I thought NULL equated to zero or false.

From comments: My program seems to always crash when I attempt a while (!list) but never the former. Each node contains a void pointer to a piece of data and a pointer to the next node.

Upvotes: 0

Views: 91

Answers (2)

George Sovetov
George Sovetov

Reputation: 5238

In most cases, it's matter of style. Comparison to NULL is more explicit.

As mentioned above, if(ptr != NULL) is equivalent to if(ptr).

Upvotes: 1

axiac
axiac

Reputation: 72226

while (list != NULL) is not the same as while (!list). They are opposites! Of course your program crashes, it tries to de-reference a NULL pointer.

while (list != NULL) is the same as while (list).

Upvotes: 5

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