Re: Compiling expressions

glen herrmannsfeldt <>
Sat, 29 Dec 2012 23:33:36 +0000 (UTC)

          From comp.compilers

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Compiling expressions (James Harris) (2012-12-29)
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Re: Compiling expressions (James Harris) (2013-01-02)
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From: glen herrmannsfeldt <>
Newsgroups: comp.compilers
Date: Sat, 29 Dec 2012 23:33:36 +0000 (UTC)
Organization: NNTP Server
References: 12-12-035
Keywords: parse
Posted-Date: 30 Dec 2012 16:37:55 EST

James Harris <> wrote:

> Compiling expressions is turning out to be more 'interesting' than I
> anticipated! My requirements I believe to be fairly generic but they
> seem not to be supported by standard algorithms so it's not as simple
> as it might be. I thought I would post here as much out of interest as
> anything. I'm not after a prebuilt solution but would be interested to
> hear from other folks who have had similar issues to address. The
> requirements are:

> 1. Hand-written, not the output of a parser generator.

An interesting requirement.

I can understand need for speed, size, and such, and maybe one
of those requires a hand-written (hand optimized) parser.

If you are so restricted, do you allow your parser to be written
in a high-level language? To be compiled by a non-handwritten

> 2. Efficient and without backtracking.

Seems reasonable to me, though the languages has to allow for it.

> 3. Precedences (and possibly associativities) defined in tables.

Tables most easily generated automatically, by a parser generator?

> 4. Output to be a tree structure.

> 5. Parenthesised subexpressions allowed.

> 6. Some operator families are *not* to associate with each other.
> See below.

So you generate an error when such occurs. The usual problem is
to make the error message good enough that one can figure out
what happened.

> 7. Monadic prefix, dyadic infix and monadic postfix operators are all
> allowed.

> 8. Prefix and infix operators can use some same symbols (e.g. minus
> sign).

> Infix and postfix operators use distinct symbols. For example, if a
> certain symbol were used as a postfix operator it could not also be
> used as an infix operator.


-- glen

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