Does float type coercion always yield the same result as static_cast? [duplicate]

Question

Dear fellow stackoverflowers,

Is there some kind of guarantee that coercing a float type to a "wider" one, always yields the same result as performing the according static_cast?

Here an example:

float f = <any float>; double a = f; double b = static_cast<double>(f); // does this always hold? EXPECT_TRUE(a==b);

Thank you for the information.

This is explicitely not true for NaNs. As NaNs are defined to not equal anything including themselves. But thats not really what your question is asking so just adding as a comment. — Mike Vine
– Mike Vine, Commented Apr 23, 2019 at 12:09
gcc will create the same assembler instruction out of it: godbolt.org/z/i7K_vw — mch
– mch, Commented Apr 23, 2019 at 12:12
Note that double can hold any value of float if represented according to IEEE 754. There is therefore no loss of precision (no rounding, etc.). — Daniel Langr
– Daniel Langr, Commented Apr 23, 2019 at 12:17

eerorika · Accepted Answer · 2019-04-23 12:13:34Z

Does float type coercion always yield the same result as static_cast?

It seems that by type coercion, you refer to implicit conversion. The answer is yes: If there is an implicit conversion from one type to another, then static cast performs that same conversion.

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