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c++castingconstants

c++ const convert

Possible Duplicate:
why isnt it legal to convert (pointer to pointer to non-const) to a (pointer to pointer to a const)

I have a function:

bool isCirclePolygonIntersection(const Point*, const int*, const Point*,
                                 const Point**, const int*);

and I'm trying to call it like this:

isCirclePolygonIntersection(p, &r, poly_coord, poly, &poly_size)

where poly defined like this:

Point** poly = new Point*[poly_size];

and there is a compiler error when I'm trying to compile it:

error C2664: 'isCirclePolygonIntersection' : cannot convert parameter 4 from 'Point **' to 'const Point **'
1>          Conversion loses qualifiers

from what I've learned is that you cannot give const argument to function when a function expects a non const argument, but it's fine otherwise. Does anyone knows what is the problem?? Thanks.

Solution

  • Parashift has a great explanation on why this is prohibited:

    http://www.parashift.com/c++-faq-lite/const-correctness.html#faq-18.17