Re: Best language for implementing compilers?

On 2019-03-10, George Neuner <gneuner2@comcast.net> wrote:
> On Sat, 9 Mar 2019 01:47:38 -0500 (EST), mertesthomas@gmail.com wrote:
>
>>For parsing I don't think that pattern matching leads to correct
>>results in all cases. I have seen too much buggy attempts to do
>>parsing with pattern matching.
>
> You have seen the approach of bad patterns - you have not seen that
> patterns are a bad approach.
>
> I also have seen some poor attempts made using pattern matching - when
> the patterns are too general, or don't cover 100% the intended cases -
> there will be unintended matches. Pattern matching is only as


Sometimes unintended matches are better; you can deal with the
over-match easily later in the pipeline.


Lisp is a good example: any possible tree shape, containing any symbols,
can be scanned into a tree. Then macros and operators check for invalid
syntax.


In C, any combination of type specifiers and qualifiers can occur in a
declaration. For instance the simple grammar will match
"long char unsigned short int double".


Enforcing the permissible combinations is a constraint check.


The valid combinations can occur in any order: unsigned long int, int
long unsigned, ...


It would be a fool's errand to write phrase structure rules to match the
valid combinations and not match invalid ones.

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