printing float as a hex number

[Kenshinofkin]

hello all

If a user enters a floatint point number like 10.1, I want to print out the hex number in floating point. The %X specifer allows for an int to be printed as a hex number and I heard you could do the samething with floating point numbers with casting and pointers but I can't seem to figure it out. Anyone have any ideas? Thanks

[guestgulkan]

I'm sure somewhere there is some archaic definition of a hexadecimal floating point specification.

However if you want a translation of a literal such as 10.1 (decimal) to A.1999999999 (hexadecimal) - that is stright forward enough, I remember the formula from myschool days.

But to be able to cast a floating point to a hexadecimal - I've never heard of such a thing in C/C++ - there is no such intrinsic C/C++ type as hexadecimal floating point. (in JAVA mayhaps).

[firedraco]

You could try analyzing the data in memory to see how they store it (i.e. integer part somewhere, decimal part somewhere else) and then try to do stuff with that...but I think that it would be easiest to just do the literal translation.

[Duthomhas]

Yeah, no sense in making it hard. Just split it into whole number + fractional + exponent parts and convert the individual parts to hex. Hence:

10.11e12 == 0xA.BeC

Looks funny, but that's exactly it.

[If you are confused about the fractional part, consider multiplying the decimal number by 10eN places (where N is your significant digits), then converting, then dividing by 16eM places (where 16N == 10M). N,M can be on bit-resolution.]

Hope this helps.

[guestgulkan]

How weird .

Noticed this morning that cout has a manipulator called hexfloat which works like we described above.

[Duthomhas]

Slick! I didn't know that was there...