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`.
75 lines
1.1 KiB
Text
75 lines
1.1 KiB
Text
import Lean.Data.PersistentArray
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def check (x : IO Nat) (expected : IO Nat) : IO Unit := do
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unless (← x) == (← expected) do
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throw $ IO.userError "unexpected result"
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def f1 (xs : Lean.PArray Nat) (top : Nat) : IO Nat := do
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let mut sum := 0
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for x in xs do
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if x % 2 == 0 then
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IO.println s!"x: {x}"
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sum := sum + x
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if sum > top then
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return sum
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IO.println s!"sum: {sum}"
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return sum
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/--
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info: x: 2
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x: 4
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x: 10
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---
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info: 16
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-/
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#guard_msgs in
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#eval f1 [1, 2, 3, 4, 5, 10, 20].toPArray' 10
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/--
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info: x: 2
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x: 4
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x: 10
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-/
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#guard_msgs in
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#eval check (f1 [1, 2, 3, 4, 5, 10, 20].toPArray' 10) (pure 16)
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def f2 (xs : Lean.PArray Nat) (top : Nat) : IO Nat := do
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let mut sum := 0
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for x in xs do
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if x % 2 == 0 then
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IO.println s!"x: {x}"
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sum := sum + x
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if sum > top then
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break
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IO.println s!"sum: {sum}"
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return sum
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/--
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info: x: 100
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x: 98
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x: 96
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x: 94
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x: 92
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x: 90
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x: 88
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x: 86
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x: 84
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x: 82
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x: 80
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x: 78
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x: 100
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x: 98
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x: 96
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x: 94
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x: 92
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x: 90
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x: 88
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x: 86
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x: 84
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x: 82
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x: 80
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x: 78
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sum: 1068
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-/
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#guard_msgs in
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#eval check (f1 (List.iota 100).toPArray' 1000) (f2 (List.iota 100).toPArray' 1000)
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