sane-date-math: use Productions as objects
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@ -183,12 +183,12 @@ class ProductionContext(ParserContext):
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and then parse "all in one go", sealing away incomplete state, and converting
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the parsed tokens into actually useful abstractions (like signed numbers).
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"""
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def __init__(self, production_cls: type, grammar: ParserContext):
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self.production_cls = production_cls
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self.context = grammar
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def __init__(self, production: 'Production', context: ParserContext = None):
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self.production = production
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self.context = context if context is not None else production.grammar()
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def __repr__(self) -> str:
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return f"ProductionContext({self.production_cls.__name__!r}, {self.context!r})"
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return f"ProductionContext({self.production!r}, {self.context!r})"
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def __str__(self) -> str:
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return str(self.context)
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@ -209,23 +209,20 @@ class ProductionContext(ParserContext):
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def reduce(self) -> object:
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# XXX this ends up being a leaf -> root reduction,
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# which generally makes it harder to achieve detailed control when nesting.
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return self.production_cls.reduce(self.reduce_inner(self.context))
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return self.production.reduce(self.reduce_inner(self.context))
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class Production:
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"""
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non-generic, likely multi-token productions,
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specified in terms of other Productions and the above primitives
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"""
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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raise NotImplementedError()
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@classmethod
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def context(cls) -> ParserContext:
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return ProductionContext(cls, cls.grammar())
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def context(self) -> ParserContext:
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return ProductionContext(self)
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@classmethod
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def reduce(cls, inner: object) -> object:
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def reduce(self, inner: object) -> object:
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"""
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use to construct the outer types out of already-converted inner types.
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e.g. Number = Then([optional(Minus), Digits, optional(Suffix)])
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@ -236,25 +233,22 @@ class Production:
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class DigitProduction(Production):
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""" one digit token """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return WantToken(DIGITS)
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@staticmethod
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def reduce(inner: Token) -> int:
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def reduce(self, inner: Token) -> int:
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return int(inner.c)
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class IntProduction(Production):
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""" multi-digit integer """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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DigitProduction,
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optional(IntProduction),
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DigitProduction(),
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optional(IntProduction()),
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])
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@staticmethod
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def reduce(inner: list) -> int:
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def reduce(self, inner: list) -> int:
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# TODO: wrong associativity
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leading, trailing = inner
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if trailing is None:
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return leading
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@ -264,14 +258,13 @@ class IntProduction(Production):
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class DurationOrIntProduction(Production):
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# due to a lack of lookahead, we combine duration and int parsing into one production
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# because a duration shares a complete int as prefix
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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IntProduction,
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IntProduction(),
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optional(WantToken(Token('d'))),
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])
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def reduce(inner: list) -> 'Literal':
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def reduce(self, inner: list) -> 'Literal':
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value, suffix = inner
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if suffix is None:
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return Literal(value)
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@ -279,46 +272,41 @@ class DurationOrIntProduction(Production):
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return Literal(timedelta(value))
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class Whitespace(Production):
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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WantToken(SPACE),
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optional(Whitespace),
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optional(Whitespace()),
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])
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class ParenthesizedExpr(Production):
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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WantToken(OPEN_PAREN),
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Expr,
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Expr(),
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WantToken(CLOSE_PAREN),
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])
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def reduce(inner: list) -> object:
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def reduce(self, inner: list) -> 'AstItem':
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open, expr, close = inner
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return expr
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class IdentifierTail(Production):
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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WantToken(ALPHA_NUM_UNDER),
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optional(IdentifierTail),
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optional(IdentifierTail()),
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])
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class Identifier(Production):
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""" variable-style identifier, e.g. 'TODAY' """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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WantToken(ALPHA_UNDER),
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optional(IdentifierTail),
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optional(IdentifierTail()),
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])
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@staticmethod
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def reduce(inner: list) -> 'Literal':
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def reduce(self, inner: list) -> 'Literal':
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# fold the tokens into a string
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first, rest = inner
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head = first.c
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@ -329,46 +317,41 @@ class Identifier(Production):
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class UnaryExpr(Production):
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""" some expression which does not invoke any operators at the outermost level """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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optional(Whitespace),
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optional(Whitespace()),
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Choice([
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DurationOrIntProduction,
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Identifier,
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ParenthesizedExpr,
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DurationOrIntProduction(),
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Identifier(),
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ParenthesizedExpr(),
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]),
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optional(Whitespace),
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optional(Whitespace()),
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])
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@staticmethod
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def reduce(inner: list):
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def reduce(self, inner: list):
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# drop the whitespace
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leading, primary, trailing = inner
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return primary
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class ExprRHS(Production):
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""" right hand side of a binary operation """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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Choice([WantToken(ASTERISK), WantToken(PLUS), WantToken(MINUS)]),
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# remaining, is just another `Expr`, but we need to keep the fields expanded here to control precedence.
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UnaryExpr,
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Choice([ExprRHS, Empty()]),
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UnaryExpr(),
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Choice([ExprRHS(), Empty()]),
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])
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class Expr(Production):
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""" this is the top-level production """
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@staticmethod
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def grammar() -> ParserContext:
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def grammar(self) -> ParserContext:
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return Then([
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UnaryExpr,
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Choice([ExprRHS, Empty()])
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UnaryExpr(),
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Choice([ExprRHS(), Empty()])
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])
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@staticmethod
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def reduce(inner: list):
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def reduce(self, inner: list):
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lhs, rhs = inner
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if rhs is None: return lhs
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@ -378,11 +361,11 @@ class Expr(Production):
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# multiplication has high precedence and we grab the adjacent token ASAP
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lhs = MulOp(lhs, rhs)
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if rhs_next is not None:
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lhs = Expr.reduce([lhs, rhs_next])
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lhs = self.reduce([lhs, rhs_next])
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else:
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# reduce the rhs and *then* apply this operator
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if rhs_next is not None:
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rhs = Expr.reduce([rhs, rhs_next])
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rhs = self.reduce([rhs, rhs_next])
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if oper == PLUS:
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lhs = AddOp(lhs, rhs)
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@ -449,7 +432,7 @@ class MulOp(BinaryOp):
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def tokenize(stream: str) -> list:
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return [Token(char) for char in stream]
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def parse(ty: type, tokens: list) -> AstItem:
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def parse(ty: Production, tokens: list) -> AstItem:
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ctx = Then([ty, Empty()])
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for i, t in enumerate(tokens):
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result = ctx.feed(t)
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@ -466,7 +449,7 @@ def parse(ty: type, tokens: list) -> AstItem:
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def evaluate(expr: str) -> object:
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tok = tokenize(expr)
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expr = parse(Expr, tok)
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expr = parse(Expr(), tok)
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print(expr)
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env = dict(
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today=datetime.now()
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