C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
(Click here for a personal note from Marshall Cline.)
Section 29:
29.1 What is this "newbie section" all about?
29.2 Where do I start? Why do I feel so confused, so stupid?
29.3 Should I use void main() or int main()?
29.4 Should I use f(void) or f()?
29.5 What are the criteria for choosing between short / int / long data types?
29.6 What the heck is a const variable? Isn't that a contradiction in terms?
29.7 Why would I use a const variable / const identifier as opposed to #define?
29.8 Are you saying that the preprocessor is evil?
29.9 What is the "standard library"? What is included / excluded from it?
29.10 How should I lay out my code? When should I use spaces, tabs, and/or newlines in my code?
29.11 Is it okay if a lot of numbers appear in my code?
29.12 What's the point of the L, U and f suffixes on numeric literals?
29.13 I can understand the and (&&) and or (||) operators, but what's the purpose of the not (!) operator?
29.14 Is !(a < b) logically the same as a >= b?
29.15 What is this NaN thing?
29.16 Why is floating point so inaccurate? Why doesn't this print 0.43?
29.17 Why doesn't my floating-point comparison work?
29.18 Why is cos(x) != cos(y) even though x == y? (Or sine or tangent or log or just about any other floating point computation)
29.19 What is the type of an enumeration such as enum Color? Is it of type int?
29.20 If an enumeration type is distinct from any other type, what good is it? What can you do with it?
29.21 What other "newbie" guides are there for me?
[29.14] Is !(a < b) logically the same as a >= b?

No!

Despite what your grade school math teacher taught you, these equivalences don't always work in software, especially with floating point expressions or user-defined types.

Example: if a is a floating point NaN, then both a < b and a >= b will be false. That means !(a < b) will be true and a >= b will be false.

Example: if a is an object of class Foo that has overloaded operator< and operator>=, then it is up to the creator of class Foo if these operators will have opposite semantics. They probably should have opposite semantics, but that's up to whoever wrote class Foo.