Perl is an old but notable exception. + is purely for addition in the base language.
If you try to add two strings with it, they’ll be converted to numbers based on any number-like characters they have at their left hand ends, and, if warnings are enabled (and you should definitely do that), you’ll get runtime warnings about it if there’s even anything vaguely non-numeric about them.
e.g. “1”+“11” will get you 12 with no complaint, warnings or otherwise. Not even the string “12” either, although it’s hard to determine one from the other in Perl. It’s a need-to-know kind of thing. And you generally don’t.
“a”+“bb” gives 0 as the result because they’re not numbers and “1a”+“11bb” will give 12, but these latter two will give warnings. Two each, in fact, one for each dodgy parameter.
String concatenation is done with the dot operator instead. “1”.“11” gives “111”. This comes with it’s own minor problems, but at least + is safe.
That’s because Perl doesn’t do operator overloading in general. Even the equality operator is different for strings (eq instead of ==). As a language, it may look pretty weird and lack some modern features, but the underlying design is surprisingly intelligent and consistent in many ways.
Perl’s default bitwise operators do differentiate between numbers and strings that look like numbers in a way that addition doesn’t*, and the readline/glob operator <> does different things depending on what (if anything) is between the signs.
There’s also the whole overload pragma for objects, which doesn’t affect default data types, but if you’re sufficiently perverse, you can define a String class that uses ‘+’ like JavaScript.
* in 2015, they added new operators so that those and the original operators don’t overload and have only one specific purpose if the bitwisepragma Edit: feature is turned on. You might know all this already though.
Perl is an old but notable exception. + is purely for addition in the base language.
If you try to add two strings with it, they’ll be converted to numbers based on any number-like characters they have at their left hand ends, and, if warnings are enabled (and you should definitely do that), you’ll get runtime warnings about it if there’s even anything vaguely non-numeric about them.
e.g. “1”+“11” will get you 12 with no complaint, warnings or otherwise. Not even the string “12” either, although it’s hard to determine one from the other in Perl. It’s a need-to-know kind of thing. And you generally don’t.
“a”+“bb” gives 0 as the result because they’re not numbers and “1a”+“11bb” will give 12, but these latter two will give warnings. Two each, in fact, one for each dodgy parameter.
String concatenation is done with the dot operator instead. “1”.“11” gives “111”. This comes with it’s own minor problems, but at least + is safe.
That’s because Perl doesn’t do operator overloading in general. Even the equality operator is different for strings (
eqinstead of==). As a language, it may look pretty weird and lack some modern features, but the underlying design is surprisingly intelligent and consistent in many ways.Not strictly true.
Perl’s default bitwise operators do differentiate between numbers and strings that look like numbers in a way that addition doesn’t*, and the readline/glob operator
<>does different things depending on what (if anything) is between the signs.There’s also the whole
overloadpragma for objects, which doesn’t affect default data types, but if you’re sufficiently perverse, you can define a String class that uses ‘+’ like JavaScript.* in 2015, they added new operators so that those and the original operators don’t overload and have only one specific purpose if the
bitwisepragmaEdit: feature is turned on. You might know all this already though.