2.10 User extension
defloop
, you invoke it with the same syntax that is used for iterating over sequences: {for
|as
} var [type-spec]being
{each
|the
} loop-method-name
[in
|of
]
[preposition expression]*
You use the following syntax to invoke loop methods defined withdefine-loop-method
:
{for
|as
} var [type-spec]being
{each
|the
} loop-method-name
preposition
expression
[preposition expression]+
The var argument takes on the value of each element in the data structure expression by using the loop method specified by the loop-method-name argument. The data type of var can be specified by the type-spec argument.
For the purposes of readability, the loop keywordeach
should follow the loop keywordbeing
when the reference to the elements in the data structure is singular. The loop keywordthe
is used afterbeing
when a plural reference to the elements of the data structure is made in the loop method. These keywords are syntactically equivalent; you can useeach
with plural references andthe
with singular references without signaling an error.
Iteration stops when there are no more elements in the specified expression that can be referenced in the way defined by the specified loop method.
Each loop method defined withdefine-loop-method
has a set of allowable prepositions, though most loop methods support the prepositionsof
andin
. For the purposes of parsing loop methods, the loop keywordusing
is treated as a preposition.
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