fdd5aec172
This refactors and improves the `#eval` command, introducing some new
features.
* Now evaluated results can be represented using `ToExpr` and pretty
printing. This means **hoverable output**. If `ToExpr` fails, it then
tries `Repr` and then `ToString`. The `eval.pp` option controls whether
or not to try `ToExpr`.
* There is now **auto-derivation** of `Repr` instances, enabled with the
`pp.derive.repr` option (default to **true**). For example:
```lean
inductive Baz
| a | b
#eval Baz.a
-- Baz.a
```
It simply does `deriving instance Repr for Baz` when there's no way to
represent `Baz`. If core Lean gets `ToExpr` derive handlers, they could
be used here as well.
* The option `eval.type` controls whether or not to include the type in
the output. For now the default is false.
* Now things like `#eval do return 2` work. It tries using
`CommandElabM`, `TermElabM`, or `IO` when the monad is unknown.
* Now there is no longer `Lean.Eval` or `Lean.MetaEval`. These each used
to be responsible for both adapting monads and printing results. The
concerns have been split into two. (1) The `MonadEval` class is
responsible for adapting monads for evaluation (it is similar to
`MonadLift`, but instances are allowed to use default data when
initializing state) and (2) finding a way to represent results is
handled separately.
* Error messages about failed instance synthesis are now more precise.
Once it detects that a `MonadEval` class applies, then the error message
will be specific about missing `ToExpr`/`Repr`/`ToString` instances.
* Fixes a bug where `Repr`/`ToString` instances can't be found by
unfolding types "under the monad". For example, this works now:
```lean
def Foo := List Nat
def Foo.mk (l : List Nat) : Foo := l
#eval show Lean.CoreM Foo from do return Foo.mk [1,2,3]
```
* Elaboration errors now abort evaluation. This eliminates some
not-so-relevant error messages.
* Now evaluating a value of type `m Unit` never prints a blank message.
* Fixes bugs where evaluating `MetaM` and `CoreM` wouldn't collect log
messages.
The `run_cmd`, `run_elab`, and `run_meta` commands are now frontends for
`#eval`.
99 lines
1.8 KiB
Text
99 lines
1.8 KiB
Text
def f (v : Nat) : StateRefT Nat IO Nat := do
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IO.println "hello"
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modify fun s => s - v
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get
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def g : IO Nat :=
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f 5 |>.run' 20
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/--
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info: hello
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---
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info: 15
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-/
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#guard_msgs in
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#eval (f 5).run' 20
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/--
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info: hello
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---
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info: 95
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-/
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#guard_msgs in
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#eval (do set 100; f 5 : StateRefT Nat IO Nat).run' 0
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def f2 : ReaderT Nat (StateRefT Nat IO) Nat := do
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let v ← read
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IO.println $ "context " ++ toString v
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modify fun s => s + v
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get
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/--
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info: context 10
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---
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info: 30
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-/
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#guard_msgs in
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#eval (f2.run 10).run' 20
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def f3 : StateT String (StateRefT Nat IO) Nat := do
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let s ← get
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let n ← getThe Nat
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set $ s ++ ", " ++ toString n
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let s ← get
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IO.println s
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set (n+1)
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getThe Nat
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/--
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info: test, 10
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---
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info: 11
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-/
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#guard_msgs in
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#eval (f3.run' "test").run' 10
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structure Label {β : Type} (v : β) (α : Type) :=
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(val : α)
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class HasGetAt {β : Type} (v : β) (α : outParam Type) (m : Type → Type) :=
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(getAt : m α)
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instance monadState.hasGetAt (β : Type) (v : β) (α : Type) (m : Type → Type) [Monad m] [MonadStateOf (Label v α) m] : HasGetAt v α m :=
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{ getAt := do let a ← getThe (Label v α); pure a.val }
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export HasGetAt (getAt)
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abbrev M := StateRefT (Label 0 Nat) $ StateRefT (Label 1 Nat) $ StateRefT (Label 2 Nat) IO
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def f4 : M Nat := do
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let a0 : Nat ← getAt 0
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let a1 ← getAt 1
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let a2 ← getAt 2
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IO.println $ "state0 " ++ toString a0
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IO.println $ "state1 " ++ toString a1
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IO.println $ "state1 " ++ toString a2
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pure (a0 + a1 + a2)
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/--
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info: state0 10
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state1 20
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state1 30
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---
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info: 60
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-/
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#guard_msgs in
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#eval f4.run' ⟨10⟩ |>.run' ⟨20⟩ |>.run' ⟨30⟩
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abbrev S (ω : Type) := StateRefT Nat $ StateRefT String $ ST ω
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def f5 {ω} : S ω Unit := do
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let s ← getThe String
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modify fun n => n + s.length
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pure ()
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def f5Pure (n : Nat) (s : String) :=
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runST fun _ => f5.run n |>.run s
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/-- info: (((), 21), "hello world") -/
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#guard_msgs in
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#eval f5Pure 10 "hello world"
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