Initialize a variable statically (at compile time)

Question

1) I have many constants in my C algo. 2) my code works both with a floating point and with a fixed point.

Right now, these constants are initialized by the float2fixed function, in which it does nothing at a floating point, but finds its representation with a fixed point at a fixed point. For example, 0.5f remains equal to 0.5f if it works with a floating point, while it uses the pow () procedure and becomes 32768 if it works at a fixed point, and the fixed-point representation is Qx.16.

This is easy to maintain, but it takes a long time to calculate these constants at a fixed point (pow is a floating-point function). In C ++, I would use some metaprogramming, so the compiler calculates these values ​​at compile time, so there is no hit at run time. But in C, this is not possible. Or that? Does anyone know such a trick? Is any compiler smart enough for this?

Waiting for any answers.

A

Answer 1

Instead of using (unsigned)(x*pow(2,16))to convert your fixed point, write it as(unsigned)(0.5f * (1 << 16))

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Answer 2

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const double somename = 3.14159;

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const fixedpoint_t somename = { ...whatever is needed... };

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datafile.c:   datafile.constants converter
        converter datafile.constants > datafile.c

Answer 3

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Answer 4

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