[Haskell-cafe] let and fixed point operator

Andrew Coppin andrewcoppin at btinternet.com
Thu Aug 30 13:16:12 EDT 2007

OK, so it's only tangentally related, but... do you have *any idea* how 
many times I've written something like

  let x = (some complex function of x)
  in (some other complex function of x)

when in fact what I *meant* to do was type x' instead of x?!

It's really maddening to write 50,000 lines of code, eventually get it 
to compile, run it, and have the program lock up and start consuming so 
much virtual memory that the entire PC becomes unstable within seconds. 
(This isn't helped by the fact that Ctrl+C doesn't seem to make either 
GHCi or GHC-compiled programs halt...) Now you have 50,000 lines of 
otherwise untested code, and there's a bug within it *somewhere*... good 

Obviously you might very well have *meant* to write x = f x. But would 
it be possible to add some kind of optional compiler warning to find 
such assignments? It can be a nightmare trying to track down where you 
made the mistake...

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