The dot (.
) operator is used to access a member of a struct, while the arrow operator (->
) in C is used to access a member of a struct which is referenced by the pointer in question.
The pointer itself does not have any members which could be accessed with the dot operator (it's actually only a number describing a location in virtual memory so it doesn't have any members). So, there would be no ambiguity if we just defined the dot operator to automatically dereference the pointer if it is used on a pointer (an information which is known to the compiler at compile time afaik).
So why have the language creators decided to make things more complicated by adding this seemingly unnecessary operator? What is the big design decision?
This question is related to
c
pointers
dereference
Structure in C
First you need to declare your structure:
struct mystruct{
char element_1,
char element_2
};
Instantiate C structure
Once you declared your structure , you can instantiate a variable that has as type your structure using either:
mystruct struct_example;
or :
mystruct* struct_example;
For the first use case you can access the varaiable eleemnet using the following syntax: struct_example.element_1 = 5;
For the second use case which is having a pointer to variable of type your structure, to be able to access the variable structure you need an arrow:
struct_example->element_1 = 5;
Beyond historical (good and already reported) reasons, there's is also a little problem with operators precedence: dot operator has higher priority than star operator, so if you have struct containing pointer to struct containing pointer to struct... These two are equivalent:
(*(*(*a).b).c).d
a->b->c->d
But the second is clearly more readable. Arrow operator has the highest priority (just as dot) and associates left to right. I think this is clearer than use dot operator both for pointers to struct and struct, because we know the type from the expression without have to look at the declaration, that could even be in another file.
C also does a good job at not making anything ambiguous.
Sure the dot could be overloaded to mean both things, but the arrow makes sure that the programmer knows that he's operating on a pointer, just like when the compiler won't let you mix two incompatible types.
Source: Stackoverflow.com