I have two questions about using the Double data type and the operations in the Floating typeclass on a computer that uses IEEE floating point numbers. I notice that the Floating class only provides "log" (presumably log base 'e') and "logBase" (which, in the latest source that I see for GHC is defined as "log y / log x"). However, in C, the "math.h" library provides specific "log2" and "log10" functions, for extra precision. A test on IEEE computers (x86 and x86-64), shows that for a range of 64-bit "double" values, the answers in C do differ (in the last bit) if you use "log2(x)" and "log10(x)" versus "log (x) / log(2)" and "log(x) / log(10)". I am under the restriction that I need to write Haskell programs using Double which mimic existing C/C++ programs or generated data sets, and get the same answers. (It's silly, but take it as a given requirement.) If the C programs are using "log2", then I need "log2" in the Haskell, or else I run the risk of not producing the same answers. My first thought is to import "log2" and "log10" through the FFI. I was wondering if anyone on Haskell-Cafe has already done this and/or has a better suggestion about how to get specialized "log2" and "log10" (among the many specialized functions that the "math.h" library provides, for better precision -- for now, I'm just concerned with "log2" and "log10"). My second question is how to get at the IEEE bit representation for a Double. I am already checking "isIEEE n" in my source code (and "floatRadix n == 2"). So I know that I am operating on hardware that implements floating point numbers by the IEEE standard. I would like to get at the 64 bits of a Double. Again, I can convert to a CDouble and use the FFI to wrap a C function which casts the "double" to a 64-bit number and returns it. But I'm wondering if there's not a better way to do this natively in Haskell/GHC (perhaps some crazy use of the Storable typeclass?). Or if someone has already tackled this problem with FFI, that would be interesting to know. Thanks. Jacob