Partitioned Enclose
⊂
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Partitioned Enclose (⊂) is a dyadic function which splits its right argument into differently sized pieces as determined by the left argument.
Basic functionality
In the simplest case, and on a vector right argument, the corresponding element in the left argument indicates where divisions begin:
1 0 1 0 0 0 0⊂'HiEarth'
┌──┬─────┐
│Hi│Earth│
└──┴─────┘
Non-Boolean left argument
Almost all dialects restrict the left argument to provide only the above functionality. However, the left argument can be interpreted as a count of how many partitions begin with a particular position:
2 0 3 0 0 0 0⊂'HiEarth'
┌┬──┬┬┬─────┐
││Hi│││Earth│
└┴──┴┴┴─────┘
Short left argument
The dialects that support this extension also allow omission of trailing zeros, which is useful if the partitioning vector is generated by where's inverse:
⍸⍣¯1⊢1 1 3 3 3
2 0 3
2 0 3⊂'HiEarth'
┌┬──┬┬┬─────┐
││Hi│││Earth│
└┴──┴┴┴─────┘
Long left argument
Additional trailing empty divisions are created by adding an additional division count corresponding to the position beyond the end of the right argument:
1 0 1 0 0 0 0 1⊂'HiEarth'
┌──┬─────┬┐
│Hi│Earth││
└──┴─────┴┘
Split into lengths
This above extensions allow a simple definition of a split-into-lengths function:
Split←{⍵ ⊂⍨ ⍸⍣¯1 +\ ¯1↓1,⍺}
3 3 4 Split 'HowAreYou?'
┌───┬───┬────┐
│How│Are│You?│
└───┴───┴────┘