It would be cool if GHCi debugger could grab not only the free variables in the selected expression but, in one case, a bit more. The case is when we stop at a function definition the first time (when just entering it). In this case, the debugger should provide the bindings for the function arguments. If a function uses pattern matching or when there are multiple equations with different formal argument names then there may not be any suitable name for the for the actual argument value. Because of this, we introduce the function argument names like: _arg1, _arg2, ... _argN. Numbering starts from 1 for the first formal argument of a function.[[BR]] The special _argN names should be provided always, even when there is a unique name for the argument in the source code.

This request was discussed here: http://permalink.gmane.org/gmane.comp.lang.haskell.glasgow.user/17204