1. syntax error not flagged?
- Posted by Jim <futures8 at EARTHLINK.NET>
Oct 01, 2000
-
Last edited Oct 02, 2000
Maybe someone can explain the following, which contains a syntax error ... if
compare(a,b) then... , (should have been
equal(a,b) or compare(a,b) = 0) which is not flagged by the interpreter as an
error, and then results in the code
producing the wrong 'result'.
with trace
sequence a,b,c,result
a = "UP"
b = "DOWN"
c = "UP"
trace(1)
if compare(a,c) then
result = "right"
elsif compare(a,b) then
result = "wrong"
end if
puts(1,result&"\n")
Thanks,
Jim
2. Re: syntax error not flagged?
Jim wrote:
<snip>
> Maybe someone can explain the following, which contains a syntax error ...
if compare(a,b) then... , (should have been
> equal(a,b) or compare(a,b) = 0) which is not flagged by the interpreter as
an error, and then results in the code
> producing the wrong 'result'.
</snip>
It isn't flagged because it isn't a syntax error. Compare is a function
which takes two parameters and returns -1 if a is less than b, 0 if a is
equal to b, and +1 if a is greater than b. The if statement interprets 0 as
false and any non-zero atom as true. The usage above is equivalant to
if compare(a,b)!=0 then . . .
or
if not equal(a,b) then . . .
The problem is, of course, that the programmer probably didn't mean that.
But the interpreter can't assume that an unlikely but legal syntax is an
error. Perhaps a warning might be in order--but certainly not an error.
-- Mike Nelson
