Dyalog APL idioms


                   {} {⍺} {⍵} {⍺⍵}
 ⍴⍴⍵ ≢⍴⍵           {0} {0}¨           +/∧\⍵  +/∧\' '=⍵  ∧\' '=⍵
 0=≡⍵ 1=≡⍵ 1=≡,⍵
 0=⍴⍵ 0∊⍴⍵ ~0∊⍴⍵                 x,←⍵ x⍪←⍵
 0=⍴⍴⍵              ,/⍵ ⍪/⍵      x↓⍨←⍺        {⍵[⍋⍵ ]} {⍵[⍒⍵ ]}
 0=⊃⍴⍵ 0≠⊃⍴⍵                                  {⍵[⍋⍵;]} {⍵[⍒⍵;]}
                 ⊣/⍵ ⊢/⍵ ⊣⌿⍵ ⊢⌿⍵              {(⊂⍒⍵)⌷⍵} {(⊂⍋⍵)⌷⍵}
⍺/⍳⍵ ⍺/⍳⍴⍵       ⊃⌽⍺ ⊃⌽,⍵
                                  ~∘' '¨↓⍵
  ⍺⊃¨⊂⍵       ⎕AV⍳⍵               {(+/∨\' '≠⌽⍵)↑¨↓⍵}
  ⊃∘⍴¨⍵                *○⍵        {(∨\' '≠⍵)/⍵}         {(↓⍺)⍳↓⍵}
           ↓⍉↑⍵        ⌊0.5+⍵     {(+/∧\' '=⍵)↓⍵}