Les fonctions d'introspection

• feature-exists($feature) - Returns whether a feature exists in the current Sass runtime.
• variable-exists($name) - Returns whether a variable with the given name exists in the current scope.
• global-variable-exists($name) - Returns whether a variable with the given name exists in the global scope.
• function-exists($name) - Returns whether a function with the given name exists.
• mixin-exists($name) - Returns whether a mixin with the given name exists.
• inspect($value) - Returns the string representation of a value as it would be represented in Sass.
• type-of($value) - Returns the type of a value.
• unit($number) - Returns the unit(s) associated with a number.
• unitless($number) - Returns whether a number has units.
• comparable($number1, $number2) - Returns whether two numbers can be added, subtracted, or compared.
• call($name, $args…) - Dynamically calls a Sass function.