lean4-htt/doc/examples/ICERM2022/notation.lean
2022-07-21 08:13:20 -04:00

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import Lean
def f (x y : Nat) := x * y + 1
infixl:65 " *' " => f
#check 2 *' 3
notation "unitTest " x => Prod.mk x ()
#check unitTest 42
notation "parenthesisTest " x => Nat.sub (x)
#check parenthesisTest 12
def Set (α : Type u) := α → Prop
def setOf {α : Type} (p : α → Prop) : Set α := p
notation "{ " x " | " p " }" => setOf (fun x => p)
#check { x | x ≤ 1 }
notation "cdotTest " "(" x ", " y ")" => Prod.map (· + 1) (1 + ·) (x, y)
#check cdotTest (13, 12)
notation "tupleFunctionTest " "(" x ", " y ")"=> Prod.map (Nat.add 1) (Nat.add 2) (x, y)
#check tupleFunctionTest (15, 12)
notation "diag " x => Prod.mk x x
#check diag 12
open Lean Meta PrettyPrinter Delaborator SubExpr in
@[delab app.Prod.mk] def delabDoubleRhsTest : Delab := do
let e ← getExpr
let #[_, _, x, y] := e.getAppArgs | failure
guard (← isDefEq x y)
let stx ← withAppArg delab
`(diag $stx)
#check diag 3
#check (3, 3)
#check (3, 4)
#check (2+1, 3)
#check (true, true)