DIP 1018--The Copy Constructor--Formal Review

[Walter Bright]

I agree with your point that C++ const can be used in a lot more places than D 
const. Absolutely true.

Missing from the post, however, is an explanation of what value C++ const 
semantics have. How does it:

1. make code easier to understand?
2. prevent common programming bugs?
3. help with multithreaded coding problems?
4. improve code generation?

I know technically what it does (after all, I implemented it), but its value 
escapes me.