the C++ test case (w = 86.7, h = 1.7) was problematic because the orer of operations affected the result. removed.

In Rust, there is a distinction between to_ascii_lowercase and to_lowercase.
to_ascii_lowercase is specifically designed for ASCII characters, while to_lowercase is used for Unicode characters.
to_lowercase function should be used for general case conversion of characters, including non-ASCII characters.
This is due to the fact that Rust doesn't simplify for you the strings.
"hello world" has obviously 11 characters, but it is not always 8 bit each, hence, the necessity for different methods based on the type.
I'm studying rust, and maybe my explanation it is not 100% correct. The free microsoft course for Rust explains very well strings, but the rust doc go deep inside the problem: https://doc.rust-lang.org/std/primitive.char.html

But there's no harm in doing that.

I've asked my friends, who did same things. I think that just lack of understanding, like "I return 'num' but result of equation is hung in the air... Somewhere".

just return health > 0;
true and false part is just waste

just seeing it now i thought const int will not be able to store in an int

Why those casts to integer?

Amazing... ;-) :-D

I can not count, MAX_CHARS_PER_LINE should be 14 and not 15 characters.
What a waste of memory ;-)

I think counting with a max line of 14 characters (10 * 10 = 100\n) and this 10 times it should rather calloc 140 + 1 for the terminating \0. About this + 1 I am still not sure.

This will crash when a and/or b is 0.

No it's not good. The comment just tells what the code is already saying.

It is redundant, pointless and in a larger context could get out-of-date soon.

Way better is to say why something happens instead of what is happening.