🚀 go-pugleaf

I am still really confused about the use of the const qualifier.  I'd be
grateful if someone could point me at a clear demonstration of its use.

I have a function which takes a parameter that is a 2 dimensional array
which it will never modify.  A similar function takes the same parameter
type but does modify its contents.  To make it clear I thought I'd make
the former have a const qualified argument.  Except for a recently
patched IBM ANSI C compiler, all the ANSI C compilers here complain
about the following:

	extern void
	fn(const float colours[][3]);

	static float colours[][3] = { { 1.0, 0.0, 0.0 } };

	fn2(void)
	{
		fn(colours);
	}

The complaint is the parameter in the call to fn() does not match the
prototype.  The compilers seem much happier if the call is changed to:

		fn((const float (*)[3])colours);

Why should the cast be necessary?

The DEC complaint is at least amusing:

const.c:9:  error:  In this statement, the referenced type of the
pointer value "colours" is "array [3] of float", which is not compatible
with "array [3] of float".

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