Monadic Left Shoe Underbar means

Nest

      ⊆ 'this'
┌────┐
│this│
└────┘
      ⊆ 'this' 'that'
┌────┬────┐
│this│that│
└────┴────┘

Dyadic Left Shoe Underbar means

Partition

      1 0 0 1 1 ⊆ 1 2 3 4 5
┌─┬───┐
│1│4 5│
└─┴───┘
       1 1 2 2 2⊆⍳5
┌───┬─────┐
│1 2│3 4 5│
└───┴─────┘
    ' ' (≠⊆⊢) ' many a  time'
┌────┬─┬────┐
│many│a│time│
└────┴─┴────┘

Language Elements