Corona688 -
Thanks for replay. Not what I have asked, but appreciate attention!

'Spare'=='Sparse', thank for correction and sorry for misspelling.
Regarding the >>enum E_TYPE {1,4,2};<< I actually mean to have an ability to define an association like: typedef enum E_TYPE {1=0,4=1,2=2} E_TP; (Agree, looks ugly, but why not?)
So use it like " int a = (E_TP)4;" and get a==1.
Would be usefull

Unfortunately, your code is not appliable to my intention.

First:
to have an element the loop should be used: I would like to avoid run a loop on any info-by-key request!
Whith loop my task could be done absolutely simple:

Code:

  struct { int key,val; }INF[] = {{10,5},{20,4},{40,8}};
  int get_val(int key) {
    int i;
    for(i; i<(sizeof(INF)/sizeof(INF[0]);i++) 
       if (INF[i].key==key) return INF[i].val;
  }

That it! No any smart structure with the conditions static members, no any extra complication with pointing to internal member-array, no any dynamic allocations.
(BTW, in your example it is completely unneeded: assign values in declaration and define 'p' as sized array, if you use '16' in function.)

Second: My 'big point' is to define a data construction and avoid as possible any run-time functionality to get a value (except some initialization on beginning)


I'l try to explain again:

I have in a header file an INF array of structures with two integers .
I would like to construct a way to access second value by the first one.
And I'd like to do it WITHOUT any loop through whole INF array!

Also, I going to be able to make changes in the header file without touching the source code when I need add, change or remove a pair in the INF array.

If it would be not integer 'key', I would implement it with 'enum', having a reference-array, that by enumerated values (by default - the same as an array is indexed) would return the INF array index for member with 'key'-label (the enumeration element). By that I would heve the val-value!
That array would be initialized on beginning by one time loop through the INF array and assigning the INF index to the REF-array element with the index==enumerated value of the first INF int: key!
(Hope, now I have better explained what I am looking for?)