switchcase

A switch statement is a control flow construct that selects one of several possible execution paths based on the value of an expression. It is commonly used as an alternative to long chains of if-else-if statements, providing a clear and potentially more efficient dispatch mechanism.

In languages such as C, C++, Java, and JavaScript, a typical switch statement follows this form: switch (expression) { case value1: statements; break; case value2: statements; break; ... default: statements; } The switch evaluates the expression and transfers control to the first matching case label. The break statements prevent fall-through to subsequent cases; omitting break can cause execution to continue into the following case.

Semantics and applicability vary by language. In C and C++, switch expressions are usually integral types or enums, and matching is by exact value. In JavaScript, switch uses strict comparison, and cases may be numbers or strings. Some languages support string switches, while others restrict cases to enumerated constants. Languages with pattern matching extend the switch idea to match on more complex conditions or structures.

Modern languages broaden switch with features such as pattern matching and switch expressions. Pattern matching switches can destructure values and route execution based on type or shape, as seen in Kotlin, Scala, and Rust. Some languages allow a switch to yield a value, enabling it to be used as an expression rather than a statement.

Advantages include potential performance optimizations for dense case labels and clearer dispatch logic. Drawbacks include fall-through bugs, reduced readability with many cases, and maintenance challenges when case values evolve. Alternatives include if-else chains, dispatch tables, and pattern-matching constructs.