Antoon Pardon wrote:
> On 5/09/19 15:30, Peter Otten wrote:
>> Can you provide some context?
>
> Sure I am researching the possibility of writing an easy to use
> lexing/parsing tool. The idea is to write your lexer/parser as
> follows:
>
> class Calculator(metaclass = ...):
> def __init__(self):
> self.names = set()
> self.table = {}
>
> @token(r'\d+')
> def NUMBER(self, st):
> return int(st)
>
> @token(r'\w+')
> def VAR(self, st):
> self.names.add(st)
> return st
>
> @production(r"VAR '=' NUMBER")
> def assign(self, prd):
> name = prd[0]
> val = prd[1]
> if name in self.names:
> self.table[name] = value
> else:
> raise CalcError("variable (%s) not available" % name)
>
> calc = Calculator()
> calc("a = 7")
>
> So the token en production decorators register a regex/prodcution with
> a specific method to be called in specific circumstances when parsing
> a string.
>
> So I need the lexing and parsing algorithms available to this class,
> either by adding methods to the class or by making a subclass of the
> class where they are implemented.
Ok, that looks like a nice interface to me, and I don't expect the metaclass
dance to make it harder to implement than necessary ;)
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