(lispref.info)Numbers


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Numbers
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   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 an exponential notation as well: thus, 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.
* Bitwise Operations
Logical and, or, not, shifting.
* Transcendental Functions
Trig, exponential and logarithmic functions.
* Random Numbers
Obtaining random integers, predictable or not.

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