Type System

is-function

Description: Checks if a type is a function type.

Parameters:

  • Type: The type atom to be checked.

Return: True if the type is a function type, False otherwise.

Example:

!(is-function (-> Atom Atom)) ; Returns True
!(is-function Atom) ; Returns False

type-cast

Description: Attempts to cast an atom to a specific type within an atomspace context.

Parameters:

  • Atom: The atom to cast.

  • Type: The target type.

  • Space: The atomspace to use as context.

Return: The atom if casting is successful, or an Error atom if not.

Example:

(: type1 Type)
!(type-cast A type1 &self) ; A
!(type-cast 1 type1 &self) ; Error 1 BasType

match-types

Description: Checks if two types can be unified and returns one value if so, another - otherwise.

Parameters:

  • Type1: The first type.

  • Type2: The second type.

  • Then: Atom to be returned if types can be unified.

  • Else: Atom to be returned if types cannot be unified.

Return: Third or fourth argument

Example:

!(match-types Atom Atom "Matched!" "Didn't match") ; Returns "Matched!"
!(match-types Atom Number "Matched!" "Didn't match") ; Returns "Didn't match"

first-from-pair

Description: Gets a pair as a first argument and returns first atom from pair.

Parameters:

  • Pair: Pair.

Return: First atom from a pair.

Example:

!(first-from-pair (A B)) ; Returns A

match-type-or

Description: Checks if two types can be unified and returns result of OR operation between first argument and type checking result.

Parameters:

  • Folded: Boolean value

  • Next: First type.

  • Type: Second type.

Return: True or False

Example:

!(match-type-or True Number Number) ; Returns True
!(match-type-or False Number Number) ; Returns True
!(match-type-or True Number Bool) ; Returns True
!(match-type-or False Number Bool) ; Returns False