APL Interpreter – An implementation of APL, written in Haskell (2024)

APL Interpreter January 11, 2024 Why APL? APL is an array programming language. Its only data type is the (multidimensional) array. While this might seem like a huge limitation, the generality it provides leads to a syntax that is incredibly compact and expressive, which forces the programmer to approach problems at a higher level. I was first drawn to APL by the nature of its syntax: with the exception of user-defined variables, all built-in functions and operators are single unicode symbols. As a result, code looks like this. ⍝ My solution to day 7 of Advent of Code '23 c2n ← '23456789TJQKA' ∘ ⍳ classify ← ( 5 -≢ ⍤ ∪ ) , ( ⌈ / ( + /∘. = ⍨ )) , (( 5 ≡∪ ) × ( ⌈ / c2n)) h2n ← 13 ⊥ classify , ( ¯1 ∘ + c2n) hands bids ← ↓⍉↑ (( ' ' ∘ ≠ ) ⊆⊢ ) ¨ input bids ← ⍎ ¨ bids ⎕ ← + / ( ⍳≢ bids) × bids [ ⍋ h2n ¨ hands ] modes ← { ⍵ ≡ ⍬ : ⍬ ⋄ ∪ ⍵ ⌷ ⍨ ⊂ ( ⍸⌈ / =⊢ ) + /∘. = ⍨ ⍵ } change_joker ← { ( ⊃ 'A' , ⍨ modes (⍵ ~ 'J' )) @ ( ⍸ ⍵ = 'J' ) ⊢ ⍵ } c2n ← 'J23456789TQKA' ∘ ⍳ h2n ← 13 ⊥ (classify chan ... Read full article.