Type

Type[ expr ] returns the type of an expression, typically to check it in a condition.

Usages

`Type[ expr ] == type`

Type is mostly used in a comparison, to check what kind of expression a script variable holds. Compare with one of the type names below, or with the name of an operation or function, such as Plus, Sqrt or List.

Type name	Matches	Example	out
`NaturalNumber`	integers, also negative ones	`Type[-3] == NaturalNumber`	`True`
`FloatingPointNumber`	decimal numbers and integers, and constants such as `Pi`	`Type[2.5] == FloatingPointNumber`	`True`
`SimpleFraction`	fractions of two integers	`Type[1/2] == SimpleFraction`	`True`
`Constant`	all of the above, and `True` and `False`	`Type[Pi] == Constant`	`True`
`Boolean`	`True` and `False`	`Type[True] == Boolean`	`True`
`Variable`	variables without a value	`Type[y] == Variable`	`True`
`Mapping`	mappings such as `x -> x^2`	`Type[x -> x^2] == Mapping`	`True`
`Unit`	units such as `'m'`	`Type['m'] == Unit`	`True`
`List`, `Plus`, `Sqrt`, ...	expressions with that outer operation	`Type[x+1] == Plus`	`True`

Example	in	out
A script variable with value `π` is a constant.	`x := Pi r := Type[x] == Constant`	`r = True`
A decimal number is not a natural number.	`Type[2.5] == NaturalNumber`	`False`
A decimal number is not a simple fraction.	`Type[0.5] == SimpleFraction`	`False`
A root is not a constant type: its type is `Sqrt`.	`Type[Sqrt[2]] == Constant`	`False`

`Type[ expr ]`

On its own, Type[ expr ] returns the internal type name.

Example	in	out
An integer.	`Type[ 35 ]`	`TypeConstantNaturalNumber`
A decimal number.	`Type[ 2.5 ]`	`TypeConstantReal`
A sum.	`Type[ x + 1 ]`	`Plus`
A quantity.	`Type[ Quantity[3,'m'] ]`	`Quantity`

Details

Use == to compare types. Type[x+1] <> Plus is not evaluated in a script; use it as a condition in If, or use <<>>.
Type takes exactly one argument: Type[1, 2] is left unevaluated.

See also: EqualsEval, If, Strict