[Haskell-cafe] implicit call stacks and calling function
qdunkan at gmail.com
Mon Mar 7 23:36:03 UTC 2016
On Mon, Mar 7, 2016 at 11:46 AM, Eric Seidel <eric at seidel.io> wrote:
> The reason we provide the name of the callee is that the standard format
> for a stack trace is callee+pos :)
I guess it depends how you look at it. I'm used to caller + pos, e.g. in Java:
java.lang.RuntimeException: blah blah
Traceback (most recent call last):
File "t.py", line 2, in caller
def caller(): callee()
File "t.py", line 1, in callee
def callee(): 1/0
ZeroDivisionError: integer division or modulo by zero
The haskell version (reversed to match python) would be like:
File "Caller.hs", line 6, in callee
caller = callee 10
File "Caller.hs", line 9, in ?stack
callee _n = mapM_ print (Stack.getCallStack ?stack)
To me this seems off by one, line 6 is in 'caller', not 'callee'.
> You point about wanting the caller's name too is well-taken though. In
> most languages you can just look at the next item in the stack to grab
> the caller, but with HasCallStack there may be no next item... I doubt
> it would be hard to add the caller's name too, I'd be happy to look into
> it post-ICFP. Would you mind filing a ticket?
In it I suggested adding a Stack.getFrames :: [Stack.Frame], Frame
could then have callee and srcloc fields as per getCallStack's pairs,
and add a caller field. Just a suggestion.
Thanks so much!
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