Re: Shortcut logicals

[Martin Dowie <martin.dowie@btopenworld.com>]

Robert A Duff wrote:
> Sorry, I've no idea what the Fortran rules are.
> 
> In Ada, the above expression is syntactically illegal -- compile time
> error.  You can write:
> 
>     (cond1 and cond2) and then (cond3 and cond4)
> 
> or:
> 
>     ((cond1 and cond2) and then cond3) and cond4)
> 
> for example.
> 
> "and" is just a function call.  If you say "X and Y" then X and Y are
> both evaluated (in either order) and passed to the "and" function.  The
> predefined version of "and" returns True if both are True.  But "and
> then" is a short-circuit control form: if you say "X and then Y", X is
> evaluated first, and if it's True, you're done.  Otherwise (X is False)
> Y is evaluated.

Bob,

For clarity, I think you got the last bits a little wrong... If X is 
"True" then Y is evaluated otherwise (X is "False"), Y is not evaluated.

What you said would be right if it was an "or else" short-circuit form.

Cheers

-- Martin