Switching between float and double precision at compile time

Question

Where should I look at if I want to switch between float and double precision at compile time. Its like, if user wants everything in float instead of double precision how I can maintain this flexibility? In other words, how should I define a variable that could be either float or double precision conditionally?

Answer 1

If it is OK to make the switch at compile time, a simple typedef would do:

#ifdef USE_DOUBLES
typedef double user_data_t;
#else
typedef float user_data_t;
#endif

Use user_data_t in your code, and set USE_DOUBLES if you want doubles at compile time:

g++ -DUSE_DOUBLES=1 myprogram.cpp

Answer 2

Without knowing exactly how you intent to use the data, it's hard to recommend the correct solution.

Have a look at the union date type.

http://msdn.microsoft.com/en-us/library/5dxy4b7b(v=VS.80).aspx

Templates would also be a viable option depending on the usage.

http://msdn.microsoft.com/en-us/library/y097fkab.aspx

Answer 3

I prefer not to have #defines in my code.

I would have two different headers with two different typedefs, and allow build options to choose which header is included.