sequences.lib: indices
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8cfc644893
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@ -140,3 +140,13 @@ PRIVATE>
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: ?second ( seq -- second/f ) 1 swap ?nth ; inline
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: ?third ( seq -- third/f ) 2 swap ?nth ; inline
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: ?fourth ( seq -- fourth/f ) 3 swap ?nth ; inline
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! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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! List the positions of obj in seq
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: indices ( seq obj -- seq )
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>r dup length swap r>
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[ = [ ] [ drop f ] if ] curry
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2map
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[ ] subset ;
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