Fix constexpr cmath floor of 1 returning 0 #1232

[yousseflakhal]

Problem

The boost::math::ccmath::floor function incorrectly returns 0.0 for 1.0 in a constexpr context.

Solution

• Fixed the implementation to correctly handle 1.0.
• Added test cases in ccmath_floor_test.cpp.

Linked Issue

Fixes #1232

[ckormanyos]

Thanks for pressing on with this.

I just approved this workflow run. We must approve workflow runs for first-time contributions @yousseflakhal.

Let's let this thing run through CI now.

Cc: @mborland and @jzmaddock

[mborland]

LGTM Thanks!