Re: Production missing on page 9 of Compiler Construction

"pupeno@pupeno.com" <pupeno@pupeno.com> writes:




> E = T | A "+" T.
> T = F | T "*" F.
> F = V | "(" E ")".
> V = "a" | "b" | "c" | "d".
>
> A is being used on the right hand side without it being defined on the
> left hand side first. What am I missing?
>
> The only thing I can think of is that it is missing a production at
> first, like:
>
> A = E


Alternatively, you can simply replace the "A" by an "E". It has the
same effect as adding A = E, but it doesn't make the grammar larger.


In all likelyhood, Wirth originally used A for the German/Swiss word
"Ausdruck" (meaning "Expression") and changed it to E for "Expression"
but missed a spot.


Torben
[Thanks also to several other people who sent in similar messages. -John]

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