How to use the symbols +=, *=,-=

Question

These operands may be simple but the difficulty of finding explanations which are definitive and complete prompted me to ask. What are the character combinations containing an operand followed by an equal sign (such as *=, -=,+=, etc), what do they do and how are they useful (especially pertaining to non-numeric fields)?

Examples as well as definitions would be greatly appreciated.

Thanks

Answer 1

They are usually interpreted broadly as:

x += y    ===    x = x + y

(etc for your choice of operator)

however; some languages allow you to have a bespoke += operator*, or may interpret it differently in some scenarios; for example, in C# events, += and -= mean "subscribe via the add accessor" and "unsubscribe via the remove accessor" respectively.

Typically they are just space savers, but there can be semantic differences in some cases.

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*=where I mean: very different to just the + operator and assignment