Inkling types

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Inkling is a statically typed language, which means that each variable, constant, and parameter must have a well-defined type.

Primitives

  • number: an arithmetical value.
  • string: a sequence of one or more unicode characters.

Collections

  • Array: a non-zero-length array of same-typed values.
  • Structure: a collection of typed fields with unique names.

Inkling uses structural typing to determine equivalency between types. If the shape of the types matches, the types are considered equivalent. For example, the following types are equivalent, even though they have different names, because they are both type number:

type Type1 number
type Type2 number

User-defined types

Use the type statement to create custom types. Custom types can be used anywhere a type literal would be used.

type Height number

type Coordinate {X: number, Y: number}

type TicTacToeValue number<Blank=0, X=1, O=2>

type TicTacToeBoard TicTacToeValue[3][3]

Implicit casting

The Inkling compiler validates that values assigned to variables and parameters are compatible with the assigned type. Compatibility does not require an exact type match, it only requires:

  • the change from one type to the other has no loss of precision.
  • the value is not converted to an enumeration.

Important

The Inkling compiler always assumes the result of a mathematical operation is a number. As a result, the compiler cannot statically evaluate mathematical operations that use variables.

Assigning a number to an enumerated constraint like number<1, 2> is not allowed because the compiler cannot verify that the result belongs to the enumerated set.

Casting to a range constraint like number<1 .. 2> is allowed, but the compiler will warn that the result may be rounded to fit within the range.

For more information on range and enumeration constraints, see the Number type.

Examples of valid assignments

The following example works because the value of OneOrTwo is guaranteed to fit within the range assigned to ZeroTo100.

var OneOrTwo: number<1, 2> = 1 + 1  # Enumerated constraint
var ZeroTo100: number<0..100> = 20  # Range constraint

ZeroTo100 = OneOrTwo

The following example also works, but generates a warning that the assignment may require rounding. The compiler cannot evaluate the value of 1 + OneOrTwo statically to ensure it results in a valid range value for ZeroTo2.

var OneOrTwo: number<1, 2>  = 1 + 1
var ZeroTo2: number<0 .. 2> = 1 + OneOrTwo

Examples of invalid assignments

The following example generates a compiler error. The value of ZeroTo100 may exceed the permitted values of the range type of ZeroTo50.


var ZeroTo50: number<0..50> = 50
var ZeroTo100: number<0..100> = 20

ZeroTo50 = ZeroTo100

For more details about casting compatibility, see the relevant type documentation.