45 lines
803 B
Text
45 lines
803 B
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{Pkey}
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access a key in an event stream@section{related}
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Classes/Penvir
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@section{categories}
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Streams-Patterns-Events>Patterns>Data Sharing
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@section{description}
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Pkey simplifies backward access to values in an event being processed by link::Classes/Pbind:: or another event pattern.
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@section{ClassMethods}
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@section{method}
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new
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@section{argument}
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key
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The name of the event variable to read from.
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@section{Examples}
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@racketblock[
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// \b should thus take twice the value of \a in each event:
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p = Pbind(\a, Pwhite(1, 10, inf), \b, Pkey(\a) * 2).asStream;
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p.next(()) // for Pbind, must pass in a default event even if empty
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( 'a': 10, 'b': 20 )
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( 'a': 2, 'b': 4 )
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( 'a': 5, 'b': 10 )
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( 'a': 4, 'b': 8 )
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( 'a': 2, 'b': 4 )
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::
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]
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