global_variable_exists($name) Check whether a variable with the given name exists in the global scope (at the top level of

quote($string) Add quotes to a string if the string isn’t quoted, or returns the same string if it is.

abs($number) Returns the absolute value of a number.

length($list) Return the length of a list. This can return the number of pairs in a map as

opacity($color) Returns the alpha component (opacity) of a color. This is 1 unless otherwise specified.

hsl($hue, $saturation, $lightness) Creates a Color from hue, saturation, and lightness values

simple_selectors($selector) Returns the simple

selector_replace($selector, $original, $replacement) Replaces all instances of $original with $replacement

str_slice($string, $start-at, $end-at:-1) Extracts a substring from $string. The substring will begin at index

function_exists($name) Check whether a function with the given name exists.