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This is for consistency with the `cmark` style. Now the blocks we still pretty-print ourselves will match the bulk of them that `cmark` produces.
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2.0 KiB
This transcript demonstrates that Unison forces actions in blocks to have a return type of ().
This works, as expected:
structural ability Stream a where emit : a -> ()
ex1 = do
Stream.emit 1
Stream.emit 2
42
Loading changes detected in scratch.u.
I found and typechecked these definitions in scratch.u. If you
do an `add` or `update`, here's how your codebase would
change:
⍟ These new definitions are ok to `add`:
structural ability Stream a
ex1 : '{Stream Nat} Nat
This does not typecheck, we've accidentally underapplied Stream.emit:
ex2 = do
Stream.emit
42
Loading changes detected in scratch.u.
I found a value of type: a ->{Stream a} Unit
where I expected to find: Unit
2 | Stream.emit
3 | 42
Hint: Actions within a block must have type Unit.
Use _ = <expr> to ignore a result.
We can explicitly ignore an unused result like so:
ex3 = do
_ = Stream.emit
()
Loading changes detected in scratch.u.
I found and typechecked these definitions in scratch.u. If you
do an `add` or `update`, here's how your codebase would
change:
⍟ These new definitions are ok to `add`:
ex3 : '()
Using a helper function like void also works fine:
void x = ()
ex4 =
void [1,2,3]
()
Loading changes detected in scratch.u.
I found and typechecked these definitions in scratch.u. If you
do an `add` or `update`, here's how your codebase would
change:
⍟ These new definitions are ok to `add`:
ex4 : ()
void : x -> ()
One more example:
ex4 =
[1,2,3] -- no good
()
Loading changes detected in scratch.u.
I found a value of type: [Nat]
where I expected to find: Unit
2 | [1,2,3] -- no good
3 | ()
from right here:
2 | [1,2,3] -- no good
Hint: Actions within a block must have type Unit.
Use _ = <expr> to ignore a result.