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syntaxebnfmodula-2

Shortest REPEAT statement Modula-2

I'm doing a homework assignment in which I have been provided a snippet of text titled "EBNF Description of Modula-2's Syntax" and the question asks:

"Give an example of the shortest REPEAT statement in Modula-2. ('Shortest' means fewest number of lexemes.)"

I apologies for not being able to provide the text, it is on a page that is password protected, however the text is as the title says. Basically this is what I came up with and I want to know if this works.

The EBNF description of REPEAT and it's following statements is as such:

RepeatStatement = `REPEAT` StatementSequence `UNTIL` Expression.

StatementSequence = Statement {“;” Statement}.

Statement = [Assignment | ProcedureCall | IfStatement | CaseStatement | 
             WhileStatement | RepeatStatement | LoopStatement | 
             ForStatement | WithStatement | `EXIT`

So by this description could I simply say:

REPEAT EXIT.

and be done? or do I absolutely have to use the UNTIL and/or the full StatementSequence EBNF description?

TL;DR is the rest of the EBNF statement void if I just say EXIT?

Solution

  • Well, the EBNF is pretty clear:

    RepeatStatement = `REPEAT` StatementSequence `UNTIL` Expression.

    So you must have a REPEAT keyword, a statement sequence (which can be just EXIT), the UNTIL keyword and an expression. Only those four parts together make up a valid repeat statement ...

    So I guess something like this would be the shortest you can be:

    REPEAT EXIT UNTIL TRUE