_[_]else_

Grammatical restrictions:

Argument Position Prohibited Expression
Argument 1 current fiber

Definitions:

map, any, []→any
Source: /avail/Avail/Foundation/Early Maps
Categories: Maps, Queries
If key is a key of aMap, then answer its associated value. Otherwise, invoke else and answer its return value.
Position Name Type Description
Parameters
1 aMap map A map.
2 key any A key.
3 default []→any A function that answers the
Returns any
atom, atom, []→any
Source: /avail/Avail/Foundation/Atoms
Categories: Atoms, Queries
Answer the value associated with the property key of anAtom. If no such property exists, then answer the result of applying else.
Position Name Type Description
Parameters
1 anAtom atom An atom.
2 key atom The property key.
3 else []→any The function to apply if key is not a property of anAtom.
Returns any Either the requested property value or the result of applying else.
tuple, integer, []→any
Source: /avail/Avail/Foundation/Early Tuples
Categories: Tuples, Queries
If index is a valid subscript for aTuple, then answer the corresponding element. Otherwise, answer the result obtained by applying else.
Position Name Type Description
Parameters
1 aTuple tuple A tuple.
2 index integer An integer.
3 else []→any The function to apply if index is not a valid subscript into aTuple.
Returns any The index -th element of aTuple, or the result of applying else (if index is invalid).

Semantic restrictions:

map meta, any meta, []→any's type
Source: /avail/Avail/Foundation/Early Maps
Type Description
Parameter Types
map meta
any meta
[]→any's type
tuple meta, integer's type, (function accepting <> and returning any)'s type
Source: /avail/Avail/Foundation/Early Tuples
Type Description
Parameter Types
tuple meta
integer's type
(function accepting <> and returning any)'s type