Arrow vs dot syntax?

Question

A friend is taking a data structures course and I'm trying to explain the difference in the context of a linked list. I really should know this, but having focused on high level frameworks, I'm a little rusty. I know that "arrows are used with pointers", but that's it.

Essentially, in C, what's the difference between a dot and and an arrow when accessing a property of some variable? Also, because I'm in a particularly stupid mood, is this the same in C++, or did it change?

Also highly relevant: http://stackoverflow.com/questions/4984600/when-do-i-use-a-dot-arrow-or-double-colon-to-refer-to-members-of-a-class-in-c — jogojapan, Jun 21 '13 at 04:53
If you're *that* shaky on C syntax and concepts, you shouldn't be trying to explain things ... you'll just mislead. — Jim Balter, Jun 21 '13 at 05:04

score 6 · Accepted Answer · answered Jun 21 '13 at 04:52

6

Normally the . is used when you have a structure to access directly, and the -> when you have a pointer to a structure and need to dereference it to access the structure.

a->b is syntactic sugar for (*a).b. It's the same in both C and C++.

answered Jun 21 '13 at 04:52

Carl Norum

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score 3 · Answer 2 · answered Jun 21 '13 at 04:53

3

myPtr->someVariable is the same as (*myPtr).someVariable (dereferences myPtr, accesses the member). If you have *myPtr.someVariable it treats (myPtr.someVariable) as the pointer (access the member, dereference the whole thing as the pointer).

answered Jun 21 '13 at 04:53

Raekye

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score 1 · Answer 3 · edited Jun 21 '13 at 05:00

1

pointersomething->member

is the same thing as

(*pointersomething).member

it exists as a shortcut as one could in theory do

*pointersomething.member

But the . operators have greater precedence than * operators, so the parenthesis are necessary- and thus the arrow shortcut.

edited Jun 21 '13 at 05:00

Moshe

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answered Jun 21 '13 at 04:54

Max

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Arrow vs dot syntax?

3 Answers3

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