Essentials of Javascript - Cultural View

?: 55
echo $vehicle;
?>
'feet' );
Due to an unfortunate error in the language grammar, the implementation of ?: in PHP uses the incorrect
associativity when compared to other languages, and given a value of T for arg, the PHP equivalent of the above
example would yield the value horse instead of train as one would expect. To avoid this, nested parenthesis are
needed, as in this example:
(($arg == 'A') ? 'airplane' :
(($arg == 'T') ? 'train' :
(($arg == 'C') ? 'car' :
(($arg == 'H') ? 'horse' :
'feet'))));
This will produce the correct result of train being printed to the screen.
CFML (Railo only)
arg = "T";
vehicle = ( ( arg == 'B' ) ? 'bus' :
( arg == 'A' ) ? 'airplane' :
( arg == 'T' ) ? 'train' :
( arg == 'C' ) ? 'car' :
( arg == 'H' ) ? 'horse' :
#vehicle#
Result type
'feet' );
Clearly the type of the result of the ?: operator must be in some sense the type unification of the types of its second
and third operands. In C this is accomplished for numeric types by arithmetic promotion; since C does not have a
type hierarchy for pointer types, pointer operands may only be used if they are of the same type (ignoring type
qualifiers) or one is void or NULL. It is undefined behaviour to mix pointer and integral or incompatible pointer
types; thus
number = spell_out_numbers ? "forty-two" : 42;
will result in a compile-time error in most compilers.