Pointers are known to be a very difficult programming concept for beginners to understand and master .They are also a well-known cause of many programming bugs for both novice and experienced programmers. Pointers are cognitively difficult to understand in part because of the level of indirection that they introduce.
Ever came across a declaration like int * (* (*fp1) (int) ) [10]; or something similar that you couldn't fathom? Sometimes people get confused when more stars are thrown in. Below right-left rules are the key to read , which will allow you to interpret any C/C++ declaration accurately.
Right-Left Rules to follow for deciphering pointer declarations. These are particularly important for function pointers:-
1. Start with the name that will identify the pointer, which is known as the identifier.
2. Move to the right until you encounter a right-parentheses [symbol = ")" ] or reach the end. Do not stop if the () brackets are used to pass parameters to a function. Also do not stop on encountering brackets used with arrays: [ ].
3. Now go left of the identifier to continue deciphering the declaration. Keep going left until you find a left-parentheses [the symbol "(" ] or reach the end. Do not stop if the brackets are used to pass parameters to a function.
4. The whole interpretation should be a nice long sentence.
Here are a few examples to make the process clear:
1. int *ptr[4]
ptr is an array of size 4... [nothing more on the right]
...of pointers to an int. [nothing more to read]
2. int (*ptr) [4]
ptr is... [ the) indicates:"stop reading further to the right". Now read left.]
...a pointer to... [we encounter a ( . Now read further right.]
...an array of size 4... [nothing more on right]
...of type int. [nothing more on left]
3.
( * f1 ( ) ) ( )
1 2 3 4 5 6
f1 is a function…. [ we see a },character 5. Now read left]
[ The arguments in () at position 4 should be read as one character.
Do not stop at () that pass parameter to a function.]
…returning a pointer… [we see a (,character 1. now read right.]
…to a function… [nothing more on right]
…returning an int [not specified,but implicit]
4.
float ( * f1 ) ( )
1 2 3 4 5 6
f1 is … [we see a),character 5,so go left now]
…a pointer… [we see a (,character 2,so go right now]
…to a function… [nothing more on right,so go left now]
…returning a float. [nothing more on left]
5.
float * ( * f1 [5] ) ( )
1 2 3 4 5 6 7 8
f1 is an array of 5… [ we see character 7,so go left]
…pointers… [we see character 3,so go right]
…to a function… [nothing more on right, so go left]
…returning a pointer to float. [nothing more on left]
ref :