assignment: left-to-right or right-to-left evaluation?

[Andrei Alexandrescu]

Consider:

uint fun();
int gun();
...
int[] a = new int[5];
a[fun] = gun;
Which should be evaluated first, fun() or gun()? It's a rather arbitrary 
decision. C/C++ don't even define an order. Python chooses 
left-to-right, EXCEPT for assignment, which is right-hand side first. 
Lisp and C# choose consistent left-to-right. I don't like exceptions and 
I'd like everything to be left-to-right. However, this leads to some odd 
cases. Consider this example in TDPL:

import std.stdio, std.string;

void main() {
  uint[string] dic;
  foreach (line; stdin.byLine) {
    string[] words = split(strip(line));
    foreach (word; words) {
      if (word in dic) continue; // nothing to do
      uint newID = dic.length;
      dic[word] = newID;
      writeln(newID, '\t', word);
    }
  }
}

If we want to get rid of newID, we'd write:

      writeln(dic.length, '\t', word);
      dic[word] = dic.length;

by the Python rule, and

      writeln(dic.length, '\t', word);
      dic[word] = dic.length - 1;

by the C# rule.

What's best?


Andrei