OpenEuphoria

Re: atom() ambiguity

• Posted by "Graeme." <hmi at POWERUP.COM.AU> Jun 20, 1998
• 720 views

As I go to send this message, I see a couple
of you have already said this, but here's
my stab at it anyway.



At 10:44 AM 6/19/98 -0400, Alan wrote:

>Maybe if atom(line) then is a shorthand, but I don't think it is a good one
>because it is ambiguous.


"if atom(a) then" translates to "if atom(a)!=0 then"

It works because of the way the if..then
statement works. If..then accepts a numeric
input and branches around (skips) the enclosed
code if that input is zero.

Numeric input? Yes.
All comparisons are equated to a
numeric result, 1 for true and 0 for
false. The comparison (3=5) has a
value of 0 as three obviously does
not equal five.

You can assign the result of a comparison
to a variable;

integer comp

comp=(6=3)
print(1,comp)

The output is 0 (false)

-----------------

integer comp

comp=(5>3)+(6!=4)+(2<9)
print(1,comp)

The output is 3 (true+true+true)

-----------------

integer comp

comp=1/(2>5)

The output is division by zero (false) error

-----------------

sequence comp

comp=({3,6,8,4}>6)
print(1,comp)

The output is {0,0,1,0} (false,false,true,false)

-----------------


So, if you put "if atom(line)=1 then" in
your program, the comparison (atom(line)=1)
will be evaluated to a one or a zero and that
value will be passed to the if..then statement.
But, as you have a 1 or a 0 returned from the
type check anyway, it hardly seems worth the
effort.



Graeme.








----------------------------------------------------