alt Hacker NewsAs I recall, C# supports this in a completely sensible way by distinguishing a[i,j] and a[i][j]. If I understand right, in C, a[i][j] means what C# would spell a[i,j], which does seem rather surprising and inconsistent
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simiones • today at 8:04 AM
In C, a[i][j] can mean either a[i,j] or a[i][j], depending on the type of a.
Not quite. As GP mentions, a[i][j] might mean either, depending on what the type of a is:
(a) If the type of a is “array of length N of pointer to (say) char” (declaration: char *a[N]), then a[i][j] means the jth char in the contiguous block pointed to by the ith pointer. In C#, this is what you get with an array of arrays.
(b) If the type of a is “array of length N of array of length M of char” (declaration: char a[N][M] — sic!), then a[i][j] means the jth element of the ith element, aka the (i*M+j)th char in the single contiguous memory block. In C#, this is what you get with a two-dimensional array.
The way this happens is a bit subtle:
(a) The value a, of type “array of size N of pointer to char”, first decays into “pointer to pointer to char”, then a[i] retrieves the ith “pointer to char” starting from it as a base, then in turn a[i][j] retrieves the jth “char” starting from that as a base.
(b) The value a, of type “array of length N of array of length M of char”, first decays into “pointer to array of length M of char” (sic!), then a[i] retrieves the ith “array of length M of char” starting from it as a base, which then decays into “pointer to char”, then a[i][j] retrieves the jth “char” starting from that as a base.
NB: There are no implicit references here, unlike in C#; in part (b), a is an N*M-byte chunk of memory and a[i] is an M-byte piece of it.