have another look at
https://hackage.haskell.org/packaggetCallStackgetCallStacke/base-4.16.0.0/do...
https://hackage.haskell.org/package/base-4.16.0.0/docs/GHC-Stack.html#v:call...
You need
```
let l = getCallStack callStack
print (length l)
```
the `getCallStack` does not return an "IO" value..
On Sun, Dec 12, 2021, 12:58 Michael Turner
The following prints 1, as you'd expect: ----------------- import GHC.Stack
foo :: HasCallStack => IO () foo = do print (length (getCallStack callStack))
main = foo ------------------- But when I make it this: ... l <- getCallStack callStack ; print (length l)
I get all this: ------------------------------------------ ... • Couldn't match type ‘[]’ with ‘IO’ Expected type: IO ([Char], SrcLoc) Actual type: [([Char], SrcLoc)] • In a stmt of a 'do' block: l <- getCallStack callStack In the expression: do l <- getCallStack callStack print (length l) In an equation for ‘foo’: foo = do l <- getCallStack callStack print (length l) | 5 | l <- getCallStack callStack ; | ^^^^^^^^^^^^^^^^^^^^^^ --------------------------------------------
What am I not seeing?
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