Re: A really wacky design decision

On Sat, 03 Oct 2009 11:57:36 -0400, fsb@thefsb.org (Tom Worster) wrote: >On 10/3/09 7:21 AM, "clancy_1@cybec.com.au" <clancy_1@cybec.com.au> wrote: > >> However there is one feature of PHP which, to my mind, is really bad design. >> How many of >> you can see anything wrong with the following procedure to search a list of >> names for a >> particular name? >> >> $i = 0; $j = count ($names); while ($i < $j) >> { if ($names[$i] == $target) { break; } >> ++$i; >> } >> >> As long as the names are conventional names, this procedure is probably safe >> to use. >> However if you allow the names to be general alphanumeric strings, it is not >> reliable. One >> of my programs recently broke down in one particular case, and when I >> eventually isolated >> the bug I discovered that it was matching '2260' to '226E1'. (The logic >> of >> this is: 226E1 >> = 226*10^1 = 2260). >> >> I agree that I was well aware of this trap, and that I should not have used a >> simple >> comparison, but it seems to me to be a bizarre design decision to assume that >> anything >> which can be converted to an integer, using any of the available notations, is >> in fact an >> integer, rather than making the default to simply treat it as a string. > >this is odd. > >i might think it ok for (2260 == '226E1') to be true since php would be >doing type juggling in a logical left-to-right manner: we start with an >integer 2260, next is the juggling comparison operator, then a string, so it >might reasonably try to convert the string to an integer and then compare. > >but with ('2260' == '226E1'), where both lhs and rhs are already of the same >time, it seems elliptical, to say the least, that php should search the >types to which it can convert the strings looking for one in which they are >equal. The order doesn't matter; 2260 == 226e1, and 226e1==2260. It looks as if (for comparisons) PHP's order of preference is Integer > Real > ?? > ?? > String. If you use '==' it will try to convert everything to integer, but if you use '===' it will try to render them in some standard format (so that 226e1 === 2.26e3), but will not convert real to integer. Despite which if you print them without specifying a format it will print them all as 2260. All very messy! Clancy