"Strong typing vs. strong testing"

TheFlyingDutchman zzbbaadd at aol.com
Thu Sep 30 12:14:47 CEST 2010


>
> > "in C I can have a function maximum(int a, int b) that will always
> > work. Never blow up, and never give an invalid answer. "
>
> > Dynamic typed languages like Python fail in this case on "Never blows
> > up".
>
> How do you define "Never blows up"?

Never has execution halt.

I think a key reason in the big rise in the popularity of interpreted
languages is that when execution halts, they normally give a call
stack and usually a good reason for why things couldn't continue. As
opposed to compiled languages which present you with a blank screen
and force you to - fire up a debugger, or much much worse, look at a
core dump - to try and discern all the information the interpreter
presents to you immediately.

>
> Personally, I'd consider maximum(8589934592, 1) returning 1 as a blow
> up, and of the worst kind since it passes silently.

If I had to choose between "blow up" or "invalid answer" I would pick
"invalid answer".

In this example RG is passing a long literal greater than INT_MAX to a
function that takes an int and the compiler apparently didn't give a
warning about the change in value as it created the cast to an int,
even with the option -Wall (all warnings). I think it's legitmate to
consider that an option for a warning/error on this condition should
be available. As far the compiler generating code that checks for a
change in value at runtime when a number is cast to a smaller data
type, I think that's also a legitimate request for a C compiler option
(in addition to other runtime check options like array subscript out
of bounds).




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