Add missing std:: namespace

[dimitry-ishenko]

There are a number of small functions throughout the course that are referred to in global namespace, for example:

• fmin, fmax
• sqrt
• fabs
• sin, cos, tan
• rand

Two of them -- sqrt and fabs -- are pulled into global namespace with the using directive inside rtweekend.h, but others -- aren't. Two possible solutions:

1. Prefix all functions with std:: namespace (preferred).
2. Pull missing functions into global namespace (poor practice).

[hollasch]

I'm inclined to just pull them in to the global namespace, but agree that the approach should be consistent.

[hollasch]

@dimitry-ishenko — please create a PR adding yourself to the books/acknowledgments.md.html file, with optional hotlink.

[hollasch]

Given the fact that the standard library names above are all three or four letters in length, I think I'm just going to go with an explicit prefix. This also helps readers to get a hint about functions they do and don't need to have implemented.

[hollasch]

Ugh. All right, guess I'm going to be inconsistent. It's too painful with std::make_shared and std::shared_ptr, as that causes new line wraps all over the place, plus the fact that these two names are highly unlikely for anyone to collide with in their own implementations. Everything else will get the std:: prefix though.

[hollasch]

By the way, one thing that I'm currently puzzled by is that dropping the using statements does not cause unprefixed functions to generate errors. I'm not sure why.

[dimitry-ishenko]

By the way, one thing that I'm currently puzzled by is that dropping the using statements does not cause unprefixed functions to generate errors. I'm not sure why.

Some of these functions also exist in C. And, since most C++ compilers are also C compilers, they pull in those C headers and "re-declare" (with using) the functions inside std:: namespace. Side effect of this is that the functions end up being leaked into the global namespace.

[hollasch]

Also log, atan2.

[dimitry-ishenko]

@dimitry-ishenko — please create a PR adding yourself to the books/acknowledgments.md.html file, with optional hotlink.

@hollasch I am gonna be famous now... 😊