case>quot ( default assoc -- quot )
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Vocabulary
combinators

Inputs

default	a quotation
assoc	a sequence of pairs of quotations

Outputs

quot	a quotation

Word description
Creates a quotation that when called, has the same effect as applying case to assoc.

This word uses three strategies:

•	If the assoc only has a few keys, a linear search is generated.
•	If the assoc has a large number of keys which form a contiguous range of integers, a direct dispatch is generated using the dispatch word together with a bounds check.
•	Otherwise, an open-coded hashtable dispatch is generated.

Definition

USING: accessors assocs combinators.private kernel math
sequences words ;

IN: combinators

: case>quot ( default assoc -- quot )
    dup keys {
        { [ dup empty? ] [ 2drop ] }
        {
            [ dup [ length 4 <= ] [ [ word? ] any? ] bi or ]
            [ drop linear-case-quot ]
        }
        {
            [ dup contiguous-range? ]
            [ drop dispatch-case-quot ]
        }
        { [ dup [ wrapper? ] none? ] [ drop hash-case-quot ] }
        {
            [ dup [ wrapper? ] all? ]
            [
                drop [ [ wrapped>> ] dip ] assoc-map
                hash-case-quot
            ]
        }
        [ drop linear-case-quot ]
    } cond ;