maybe — Logtalk APIs v3.47.0 documentation

object

# `maybe`

Types and predicates for type-checking and handling optional terms. Inspired by Haskell.

Author: Paulo Moura
Version: 0:7:0
Date: 2021-01-03
Compilation flags:
`static, context_switching_calls`
Provides:
type::type/1
type::check/2
arbitrary::arbitrary/1
arbitrary::arbitrary/2
Uses:
optional
optional(Optional)
random
type
Remarks:

> - Type-checking support: Defines type `maybe(Type)` for checking optional terms where the value hold by the optional term must be of the given type.

> - QuickCheck support: Defines clauses for the `arbitrary::arbitrary/1-2` predicates to allow generating random values for the `maybe(Type)` type.

Inherited public predicates:
(none)

- Public predicates

  - `cat/2`

- Protected predicates

- Private predicates

- Operators

## Public predicates

### `cat/2`

Returns the values stored in the non-empty optional terms.

Compilation flags:
`static`
Template:
`cat(Optionals,Values)`
Mode and number of proofs:
`cat(+list(optional),-list)` - `one`

## Protected predicates

(no local declarations; see entity ancestors if any)

## Private predicates

(no local declarations; see entity ancestors if any)

## Operators

(none)

See also

optional, optional(Optional), type, arbitrary