:print and :sprint sometimes fully evaluates strings
Not too confident in my terminology but :sprinting a string that has been evaluated down to its spine seems to fully evaluate the string:
Prelude> let a = map (Debug.Trace.trace "!!!") "abc"
Prelude> a `seq` ()
()
Prelude> :sprint a
a = _ : _ -- looks fine
Prelude> length a
3
Prelude> :sprint a
a = "!!! -- strange!
a!!!
b!!!
c"What I expect to see is a = [_,_,_]. :print behaves similarly. Since neither :print nor :sprint is supposed to force any evaluation this seems like a bug. At least it can make debugging quite confusing if you're not aware of it!
Trac metadata
| Trac field | Value |
|---|---|
| Version | 7.6.3 |
| Type | Bug |
| TypeOfFailure | OtherFailure |
| Priority | normal |
| Resolution | Unresolved |
| Component | GHCi |
| Test case | |
| Differential revisions | |
| BlockedBy | |
| Related | |
| Blocking | |
| CC | hvr |
| Operating system | |
| Architecture |