object

# `maybe`

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

Author: Paulo Moura
Version: 0.5
Date: 2019/1/24
Compilation flags:
`static, context_switching_calls`
Provides:
type::type/1
type::check/2
arbitrary::arbitrary/1
arbitrary::arbitrary/2

## Public interface

### `cat/2`

Returns the terms stored in the non-empty references.

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

## Protected interface

(see related entities)

## Private predicates

(see related entities)

## Operators

(none)

## Remarks

- Type maybe(Type): Allows type-checking optional term references where 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.

See also

optional, optional(Reference), type, arbitrary