c - Does it make sense to compare which one of two points to two entries of an array is bigger? -

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in c, have array int a[20]. have 2 pointers int *pi , int *pj pointing 2 entries a[i] , a[j] respectively. don't know i , j. know if i > j or j<i or i==j.

my thought comparing pi , pjbased on pi = + i , pj=a+j. wonder if correct i > j if , if pi>pj, , i == j if , if pi==pj? thanks!

yes, < , > operators on pointers defined work in way.

and pointers don't point same object or past end of it, behavior of < , > undefined. == , != defined, though.

reference: n1570 6.5.8, paragraph 5:

when 2 pointers compared, result depends on relative locations in address space of objects pointed to. if 2 pointers object types both point same object, or both point 1 past last element of same array object, compare equal. if objects pointed members of same aggregate object, pointers structure members declared later compare greater pointers members declared earlier in structure, , pointers array elements larger subscript values compare greater pointers elements of same array lower subscript values. pointers members of same union object compare equal. if expression p points element of array object , expression q points last element of same array object, pointer expression q+1 compares greater p. in other cases, behavior undefined.


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