Chapter 3: Numbers

GNU Emacs supports two numeric data types: integers and floating point numbers. Integers are whole numbers such as -3, 0, 7, 13, and 511. Their values are exact. Floating point numbers are numbers with fractional parts, such as -4.5, 0.0, or 2.71828. They can also be expressed in exponential notation: 1.5e2 equals 150; in this example, `e2' stands for ten to the second power, and is multiplied by 1.5. Floating point values are not exact; they have a fixed, limited amount of precision.

Support for floating point numbers is a new feature in Emacs 19, and it is controlled by a separate compilation option, so you may encounter a site where Emacs does not support them.

Integer Basics Representation and range of integers.
Float Basics Representation and range of floating point.
Predicates on Numbers Testing for numbers.
Comparison of Numbers Equality and inequality predicates.
Numeric Conversions Converting float to integer and vice versa.
Arithmetic Operations How to add, subtract, multiply and divide.
Rounding Operations Explicitly rounding floating point numbers.
Bitwise Operations Logical and, or, not, shifting.
Math Functions Trig, exponential and logarithmic functions.
Random Numbers Obtaining random integers, predictable or not.

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