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The else clause in the above example is linked to the for statement, and not the inner if statement. Both Python's for and while loops support such an else clause, which is executed only if early exit of the loop has not occurred. Some languages support breaking out of nested loops; in theory circles, these are called multi-level breaks.
The most common deviation from structured programming is early exit from a function or loop. At the level of functions, this is a return statement. At the level of loops, this is a break statement (terminate the loop) or continue statement (terminate the current iteration, proceed with next iteration). In structured programming, these can be ...
Arithmetic if is an unstructured control statement, and is not used in structured programming. In practice it has been observed that most arithmetic IF statements reference the following statement with one or two of the labels. This was the only conditional control statement in the original implementation of Fortran on the IBM 704 computer. On ...
An alternative solution is to use the normal stack unwinding (variable deallocation) at function exit to unallocate resources, such as via destructors on local variables, or similar mechanisms such as Python's "with" statement. Some early implementations of languages such as the original Pascal and C restricted the types that can be returned by ...
Early BASICs (such as GW-BASIC) used the syntax WHILE/WEND.Modern BASICs such as PowerBASIC provide both WHILE/WEND and DO/LOOP structures, with syntax such as DO WHILE/LOOP, DO UNTIL/LOOP, DO/LOOP WHILE, DO/LOOP UNTIL, and DO/LOOP (without outer testing, but with a conditional EXIT LOOP somewhere inside the loop).
These are analogous to the use of a return statement in non-terminal position – not strictly structured, due to early exit, but a mild relaxation of the strictures of structured programming. In C, break and continue allow one to terminate a loop or continue to the next iteration, without requiring an extra while or if statement. In some ...
Short-circuit evaluation, minimal evaluation, or McCarthy evaluation (after John McCarthy) is the semantics of some Boolean operators in some programming languages in which the second argument is executed or evaluated only if the first argument does not suffice to determine the value of the expression: when the first argument of the AND function evaluates to false, the overall value must be ...
In methods that have a return value of type Task<T>, methods declared with async must have a return statement of type assignable to T instead of Task<T>; the compiler wraps the value in the Task<T> generic. It is also possible to await methods that have a return type of Task or Task<T> that are declared without async.