Operators for Strings

In general you cannot perform mathematical operations on Strings, even if the strings look like numbers. The following are illegal (if we know that fred has type String)

By the way, can you tell by looking at those expressions whether fred is an integer or a string? Nope. The only way to tell the type of a variable is to look at the place where it is declared.

Interestingly, the + operator does work with Strings, although it does not do exactly what you might expect. For Strings, the + operator represents concatenation, which means joining up the two operands by linking them end-to-end. So "Hello, " + "world." yields the string "Hello, world." and fred + "ism" adds the suffix ism to the end of whatever fred is, which is often handy for naming new forms of bigotry.