What does this pointer between parentheses mean?

Question

I'm having a problem to understand this line of code:

MyTable *t = (MyTable*)table;

Can someone explain what's happening on the right side of the equal sign?

score 2 · Answer 1 · answered Feb 21 '14 at 14:30

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The pointer (or whatever it is) table is casted to the type "pointer to MyTable".

answered Feb 21 '14 at 14:30

Vladimir F Героям слава

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score 1 · Answer 2 · edited May 23 '17 at 12:20

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(MyTable*) is not a pointer. It's a c-style cast to the type " pointer to MyTable" .

table is presumably a pointer which is being converted by the cast.

Please not that c-style casts are not always your best option in c++ when dealing with OO design.

See : this question for details.

Edit:

The language tag on this question was c++ at first.

edited May 23 '17 at 12:20

Community

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answered Feb 21 '14 at 14:31

OlivierLi

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Eric Postpischil · Answer 3 · 2014-02-21T14:50:43.203

The text in parentheses is not a pointer, it is a type name. MyTable * is a pointer to MyTable.

A type name in parentheses is a cast.

A cast performs a conversion.

The cast (MyTable *) converts a value to a pointer to MyTable.

There are rules for converting pointers that can be somewhat tricky, so conversions like this might or might not result in valid code. The code MyTable *t = (MyTable *) table; is probably valid code if one of the following is true:

table is already a pointer to a MyTable, either directly or by having been properly converted in various ways.
table points to (enough) space allocated with malloc or another memory-management routine.
table is equal to NULL.

The code is probably not valid if:

table points to some kind of object other than a MyTable.
table is not a pointer.

There are some other specialized situations that are valid, but I am omitting the details since they are specialized. (These include integers that have been converted from pointers and conversions between pointers to aggregates and pointers to their first elements.)

score 0 · Answer 4 · answered Feb 21 '14 at 14:30

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It is casting table to a type of "pointer to MyTable".

MyTable is a class or struct, probably. A pointer to MyTable is a type of it's own (MyTable*).

answered Feb 21 '14 at 14:30

noelicus

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Mithrandir · Answer 5 · 2014-02-21T14:36:55.670

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What is confusing you? Whatever table is, it is casted into a pointer to MyTable. This way, if the cast is possible, the assignment will be valid.

edited Feb 21 '14 at 14:36

answered Feb 21 '14 at 14:30

Mithrandir

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score 0 · Answer 6 · answered Feb 21 '14 at 16:42

MyTable t = (MyTable)table; Whenever this situation occurs think like this firstly on right: ()are evaluated first means table is converted to a pointer of type MyTable.look at following example

    when you say 
     float x;
     int y;
     x=y;//read below

when tou do x=y as type of y is int and you are assigning it to a float Here implici conversion is carried out which is

 x=(float)y;

Which is the way you are doing firstly table is converted to type MyTable* and then is assigned

What does this pointer between parentheses mean?

6 Answers6