An expression can be thought of as as a combination of constants (integer, floating point, and string), functions (built in and user defined), and operators that create a single value when the expression is evaluated.
Integer Expressions are expressions that return a whole number.
Positive integer values may also be expressed in binary (base 2), octal (base 8), and hexadecimal (base 16). Precede binary values with 0b (0b1110 = 14), octal with 0o (0o177 = 127), and hexadecimal with 0x (0xff = 255).
Expressions that return a decimal number, even if it ends in .0, are known as floating point expressions.
|Floating Point Expressions|
Very large and small floating point numbers may also be represented in scientific E notation (added in version 0.9.9.46). http://en.wikipedia.org/wiki/Scientific_notation
|Scientific E Notation|
|E Notation||Decimal Number|
Regular Expressions are just normal strings but have a specific format used in searching and replacing text.