4d7b7dd8e6
This PR generalizes the `while` syntax in `do` blocks so that the condition can be any `doIfCond`, the same condition form already accepted by `if`. As a result, `while let pat := e do …` and `while let pat ← e do …` are now supported in addition to `while cond do …` and `while h : cond do …`. The previously separate `doWhile` and `doWhileH` parsers and their accompanying macros are unified into a single `doWhile` parser whose macro delegates to the existing `doIf` desugaring.
118 lines
1.7 KiB
Text
118 lines
1.7 KiB
Text
def test2 : IO Unit := do
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let mut i := 0
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repeat
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println! "{i}"
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i := i + 1
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until i >= 10
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println! "test2 done {i}"
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/--
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info: 0
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1
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2
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3
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4
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5
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6
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7
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8
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9
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test2 done 10
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-/
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#guard_msgs in
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#eval test2
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def test3 : IO Unit := do
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let mut i := 0
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repeat
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println! "{i}"
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if i > 10 && i % 3 == 0 then break
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i := i + 1
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println! "test3 done {i}"
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/--
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info: 0
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1
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2
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3
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4
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5
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6
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7
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10
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11
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12
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test3 done 12
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-/
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#guard_msgs in
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#eval test3
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-- `while let pat := e do ...` exits when the pattern fails to match.
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def testWhileLet : IO Unit := do
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let mut xs := [0, 1, 2, 3]
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while let x :: rest := xs do
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println! "{x}"
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xs := rest
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println! "done {xs.length}"
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/--
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info: 0
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1
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2
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3
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done 0
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-/
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#guard_msgs in
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#eval testWhileLet
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-- `while let pat ← e do ...` evaluates the bind on each iteration.
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def testWhileLetBind : IO Unit := do
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let mut xs := [0, 1, 2, 3]
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while let some x ← pure xs.head? do
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println! "{x}"
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xs := xs.tail
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println! "done"
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/--
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info: 0
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1
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2
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3
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done
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-/
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#guard_msgs in
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#eval testWhileLetBind
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-- Pops entries from an `IO.Ref`-backed list to show that the bound expression
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-- in `while let pat ← e do ...` is re-evaluated each iteration.
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def testWhileLetBindRef : IO Unit := do
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let r ← IO.mkRef [0, 1, 2, 3]
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while let x :: rest ← r.get do
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println! "{x}"
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r.set rest
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println! "done {(← r.get).length}"
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/--
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info: 0
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1
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2
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3
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done 0
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-/
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#guard_msgs in
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#eval testWhileLetBindRef
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-- Unified `while` keeps supporting the `while h : cond do ...` form.
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def testWhileH (xs : Array Nat) : Nat := Id.run do
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let mut i := 0
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let mut sum := 0
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while h : i < xs.size do
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sum := sum + xs[i]
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i := i + 1
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return sum
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/-- info: 6 -/
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#guard_msgs in
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#eval testWhileH #[1, 2, 3]
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