loop

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loopstatement

Syntax   A loopStatement is:

 loop
  statementsAndDeclarations
 end loop

Description   A loop statement causes the statements (and declarations) in it to be repeatedly executed. This continues until terminated by one of its enclosed exit statements (or by an enclosed return or result statement).

Example   Output on separate lines: Happy, Happy, Happy, etc.

        loop
            put "Happy"
        end loop

Example   Read words up to the word Stop.

        var word : string
        loop
            get word
            exit when word = "Stop"
        end loop

Details   A loop statement can contain more than one exit, or none at all (in which case it is an infinite loop). When the exit when is at the beginning of the loop, the loop works like Pascal's do while; when at the end, the loop works like Pascal's repeat until.

Just preceding the statements and declarations, you are allowed to write an "invariant clause" of the form:

        invariant trueFalseExpn
This clause is equivalent to: assert trueFalseExpn.

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