From: Nick Woolley <nickwoolley@...>
Date: 2005-05-04T08:07:49+09:00
Subject: Re: Typo-checking instead of static typing

Ben Giddings wrote:
> My open question is then: how do you find typos and brainos in seldom-run 
> code in a dynamic language like Ruby?

At the risk of being jeered: I have found perl's 'use strict' with 'my' 
declarations have helped keep my feet unshot in the past.  It won't get 
everything, but misspelt variables won't pop into existance behind your 
back.  Conversely, javascript has always spent me to deadline hell with 
just this sort diabolical mischief (grr).

I've always wondered why ruby doesn't have somthing similar. Presumably 
there's some flaw/objection to the idea of having this?  But! surely 
this is exactly what Ben is asking for?

Also, conceivably, couldn't (optional) implicit run-time checks be added 
which match the declared 'type' of an assignee variable to the current 
type of the assigned object?  No type inference, just a little extra 
runtime overhead (which could be switched off).  And/or similar optional 
preconditions on method arguments?

e.g.

   Fruit var1 = Banana.new  # ok
   Flesh var2 = Sausage.new # ok
   Object var3 = Hamster.new # no checks on this var
   var3 = var2 # so, Sausages are okay here
   var3 = var1 # so are Bananas
   var1 = var2 # but not here, cos Sausages aren't Fruit - bang!
   var4 = 0 # var4 isn't predeclared - bang!

Um, this seems so obvious I am expecting someone to reveal my 
cluelessness imminently.

Nick