const arrays in prototypes

[Karl Heuer]

>In article <2781 at sunset.MATH.UCLA.EDU> pmontgom at euphemia.math.ucla.edu (Peter Montgomery) writes:
>>Suppose instead that I am passing an array argument.

You can't.  So I'll assume you meant "suppose I am passing a pointer and using
the pointer-argument syntax that resembles an array declaration."

>>How do I specify that the pointer to the array will not be altered within
>>the subroutine?

You can't.  Use the equivalent pointer syntax instead, then put the const
keyword in the right place.

>>For example, 
>>	void DISALLOW(const int mat[2][2]) {...}

The misdeclaration "int mat[2][2]" is silently converted to "int (*mat)[2]",
so what you want is
	void DISALLOW(int (*const mat)[2]) {...}
or, if you intend both the pointer and the data to be non-modifiable,
	void DISALLOW(int const (*const mat)[2]) {...}
(the first "const" may also appear before the type).

In article <1356 at crabcake> zhu at crabcake.cs.jhu.edu (Benjamin Zhu) writes:
>Use the following prototype instead:
>	void DISALLOW(const int ** const mat)

Sorry, that's not equivalent.  You've changed the semantics of his function.

Karl W. Z. Heuer (karl at ima.ima.isc.com or harvard!ima!karl), The Walking Lint