Re: PiL3: typos

["Pierre Chapuis" <catwell@...>]

> Doesn't memoization become very difficult, if at all possible, if you
> don't have pure functions? Memoization works because you can assume that
> if a function is called with the same arguments then it will give the same
> results every time so we can remember the args -> result mapping. When you
> have side-effects and mutable data it becomes very difficult. Which I
> think makes it not very usable for Lua.

Automatic memoization à la Haskell is not possible,
but there is no reason why you could not have a way
to memoize those functions you *know* are pure. It
is an idiomatic way to do dynamic programming in Lua.

If course if you apply it to a function that is *not*
pure your program will be wrong. So the difference
with a pure functional language is that the compiler
will allow you to shoot yourself in the foot...

-- 
Pierre Chapuis