[Issue 3520] std.numeric.CustomFloat horribly broken

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http://d.puremagic.com/issues/show_bug.cgi?id=3520


Rob Jacques <sandford at jhu.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sandford at jhu.edu
           Severity|normal                      |regression


--- Comment #3 from Rob Jacques <sandford at jhu.edu> 2010-04-08 09:30:55 PDT ---
There seems to be an additional problem with custom float. In DMD 2.039 and
2.042 it doesn't compile. I've developed a hack/patch around this issue.

For example:
CustomFloat!(1, 5, 10) temp;

Error: this for signfractionexponent needs to be type CustomFloat not type
CustomFloat!(1,5,10)
Error: struct std.numeric.CustomFloat!(1,5,10).CustomFloat member
signfractionexponent is not accessible
Error: template instance std.numeric.CustomFloat!(1,5,10) error instantiating

I've been able to reduce the code to a test case

struct CustomFloat(
    bool signBit,       
    uint fractionBits,  
    uint exponentBits,
//    uint bias = (1u << (exponentBits - 1)) - 1    // This is the problem
    CustomFloatFlags flags = CustomFloatFlags.all
    )
{

    float foo;
    float bar() { return foo;}
    F get(F)() { return 1; }
}

however, when I try this as independent test case, the bug isn't reproduced. 

As a quick patch I've move bias from a template parameter to the struct body as
an enum:

struct CustomFloat(
    bool signBit,       // allocate a sign bit? (true for float)
    uint fractionBits,  // fraction bits (23 for float)
    uint exponentBits,
//    uint bias = (1u << (exponentBits - 1)) - 1
    CustomFloatFlags flags = CustomFloatFlags.all)
{
    enum bias = (1u << (exponentBits - 1)) - 1;
...

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