Mathematica: How to clear the cache for a symbol, i.e. Unset pattern-free DownValues

Question

I'm a bad cacher: Sometimes, when no one is watching, I'll cache results without including the full context like so:

f[x_]:=f[x]=x+a;
a=2; f[1];
DownValues[f]

Out[2]= {HoldPattern[f[1]]:>3,HoldPattern[f[x_]]:>(f[x]=x+a)}

This leads to horribly subtle bugs, and, more importantly, to the need for clearing the cache when I change the context. One way of clearing the cache is to completely Clear the symbol and repeat the definitions, but this is not really a solution.

What I would really like is a method for clearing all pattern-free DownValues associated with a symbol.
For clarity, I'll include my present solution as an answer, but if fails on two counts

• It only clears DownValues with all-numeric arguments
• For aesthetical reasons, I'd like to avoid using Block to grab the DownValues.

Any ideas on how to improve ClearCache?

Answer 1

I've made similar functions in the past (but I can't remember where).

Does the following code do all that you need?

ClearCache[f_] := DownValues[f] = DeleteCases[DownValues[f], 
                                              _?(FreeQ[First[#], Pattern] &)]

This maybe should be extended to UpValues and SubValues. And the Head of f restricted to Symbol.