Make it possible to evaluate monadic actions when assigning record fields (<-)
It is currently not possible to build records from values resulting from monadic actions while still using the field-specifiers.
foo :: IO Int
- ..
data Bar = Bar {
barFoo :: Int
}
buildBar :: IO () buildBar = do
return Bar {
barFoo <- foo --Evaluate foo to get the Int-value }
I've found two possible ways of doing this:
- Using temporaries to evaluate the actions before assigning which doubles the number of lines: tmp <- foo return Bar {
barFoo = tmp
}
- Lifting the record constructor which prevents you from using field specifiers (and you really need field specifiers when dealing with larger records): liftM Bar foo
Trac metadata
Trac field | Value |
---|---|
Version | 6.6.1 |
Type | FeatureRequest |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | Compiler |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | Unknown |
Architecture | Unknown |