I've thought about this awhile and I simply can't think of an easy way to solve a problem. I am learning Standard ML in my free time and saw an elegant solution to a certain problem. The problem is: given a set of coins, figure out how to use the coins to make change for a given amount.

The ML solution is clean and elegant due to the use of exceptions. I cannot imagine a simple clean way to do this in Perl, but an openly soliciting such.

here is the ML solution if you are curious 


exception Change

fun change _ 0 = nil
  | change nil _ = raise Change
  | change (coin::coins) amt =
    if coin > amt then
       change coins amt
    else
       (coin :: change (coin::coins) (amt-coin))
       handle Change => change coins amt

[download]

A sample call to this might be: 

change [5,2] 16

[download]

ML has a TCL look to it, but it is a strongly typed language with an aggressively optimizing compiler that Dominus gave an interesting talk about --- if you do go read these slides, don't miss the part where ML detects an infinite loop by it's static rigorous type checking.

In reply to pathsearch/backtracking in Perl - how to solve a problem apparently requiring it? (comparison of Perl with Standard ML) by metaperl

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