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Q&A

How to get a default value from an assoc in Factor programming language

+1
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To get a value from an assoc and provide a default value if the value does not exist, I am using the following definition:

:: at-def ( key assoc default -- value ) key assoc ?at [ drop default ] when ;

Is there a more specialized word to do this? (or a different class to use?)

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1 answer

+2
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: at-default ( default key assoc -- value/default )
    at* [ nip ] [ drop ] if ; inline

100 1 H{ { 1 2 } } at-default .
2

100 10 H{ { 1 2 } } at-default .
100

You can also just do this:

H{ { 1 2 } } 1 of [ 100 ] unless* .
2

H{ { 1 2 } } 10 of [ 100 ] unless* .
100


H{ { 1 2 } } 1 of 100 or .
2

H{ { 1 2 } } 10 of 100 or .
100
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