DOC: undefined type of idouble + double

[Thomas Kuehne]

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Don Clugston schrieb am 2006-03-02:
> Thomas Kuehne wrote:
>> 
>> http://www.digitalmars.com/d/type.html
>> "Usual Arithmetic Conversions" doesn't list any of the following
>> conversions:
>> 
>> float -> cfloat
>> ifloat -> cfloat
>> double -> cdouble
>> idouble -> cdouble
>> real -> creal
>> ireal -> creal
>> 
>> http://www.digitalmars.com/d/float.html
>> "Complex and Imaginary types" documents the conversions above:
>>> There is no particular complex literal syntax, just add a real and
>>> imaginary type.
>> 
>> DMD-0.148 allows the promotion to complex types.
>
> It does, but it shouldn't.
> Adding a real and an imaginary type to form a complex is does not have 
> to involve implicit promotion to complex. In fact, it can't, because 
> then you get problems with the sign of zero.

Exactly what would be the problems besides implementation bugs?

> You need to treat "real op 
> ireal" as a special case, which return a creal. Such bugs exist 
> currently with constant folding of complex numbers.
>
> import std.math;
> import std.stdio;
>
> void main()
> {
>      real n = -0.0;          // OK
>      const real m = -0.0;    // OK
>
>      creal c = -0.0 + 3i;   // BUG: this is +0.0 + 3i
>      creal d = n + 3i;      // OK:  this is -0.0 + 3i
>      creal e = m + 3i;      // BUG: this is +0.0 + 3i
>
>      // should print "11111" actually prints "11010".
>      writefln(signbit(n), signbit(m),
> 	signbit(c.re), signbit(d.re), signbit(e.re));
> }

[snip]

Added to DStress as:
http://dstress.kuehne.cn/run/c/cdouble_07_A.d
http://dstress.kuehne.cn/run/c/cdouble_07_B.d
http://dstress.kuehne.cn/run/c/cdouble_07_C.d
http://dstress.kuehne.cn/run/c/cdouble_07_D.d
http://dstress.kuehne.cn/run/c/cdouble_08_A.d
http://dstress.kuehne.cn/run/c/cdouble_08_B.d
http://dstress.kuehne.cn/run/c/cdouble_08_C.d
http://dstress.kuehne.cn/run/c/cdouble_08_D.d
http://dstress.kuehne.cn/run/c/cdouble_09_A.d
http://dstress.kuehne.cn/run/c/cdouble_09_B.d
http://dstress.kuehne.cn/run/c/cdouble_09_C.d
http://dstress.kuehne.cn/run/c/cdouble_09_D.d
http://dstress.kuehne.cn/run/c/cfloat_07_A.d
http://dstress.kuehne.cn/run/c/cfloat_07_B.d
http://dstress.kuehne.cn/run/c/cfloat_07_C.d
http://dstress.kuehne.cn/run/c/cfloat_07_D.d
http://dstress.kuehne.cn/run/c/cfloat_08_A.d
http://dstress.kuehne.cn/run/c/cfloat_08_B.d
http://dstress.kuehne.cn/run/c/cfloat_08_C.d
http://dstress.kuehne.cn/run/c/cfloat_08_D.d
http://dstress.kuehne.cn/run/c/cfloat_09_A.d
http://dstress.kuehne.cn/run/c/cfloat_09_B.d
http://dstress.kuehne.cn/run/c/cfloat_09_C.d
http://dstress.kuehne.cn/run/c/cfloat_09_D.d
http://dstress.kuehne.cn/run/c/creal_32_A.d
http://dstress.kuehne.cn/run/c/creal_32_B.d
http://dstress.kuehne.cn/run/c/creal_32_C.d
http://dstress.kuehne.cn/run/c/creal_32_D.d
http://dstress.kuehne.cn/run/c/creal_33_A.d
http://dstress.kuehne.cn/run/c/creal_33_B.d
http://dstress.kuehne.cn/run/c/creal_33_C.d
http://dstress.kuehne.cn/run/c/creal_33_D.d
http://dstress.kuehne.cn/run/c/creal_34_A.d
http://dstress.kuehne.cn/run/c/creal_34_B.d
http://dstress.kuehne.cn/run/c/creal_34_C.d
http://dstress.kuehne.cn/run/c/creal_34_D.d

Thomas


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