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"""
pint.facets.context.definitions
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
:copyright: 2022 by Pint Authors, see AUTHORS for more details.
:license: BSD, see LICENSE for more details.
"""
from __future__ import annotations
import numbers
import re
from dataclasses import dataclass
from typing import TYPE_CHECKING, Any, Callable, Dict, Tuple
from ...definitions import Definition
from ...errors import DefinitionSyntaxError
from ...util import ParserHelper, SourceIterator
from ..plain.definitions import UnitDefinition
if TYPE_CHECKING:
from ..plain.quantity import Quantity
_header_re = re.compile(
r"@context\s*(?P<defaults>\(.*\))?\s+(?P<name>\w+)\s*(=(?P<aliases>.*))*"
)
_varname_re = re.compile(r"[A-Za-z_][A-Za-z0-9_]*")
# TODO: Put back annotation when possible
# registry_cache: "UnitRegistry"
class Expression:
def __init__(self, eq):
self._eq = eq
def __call__(self, ureg, value: Any, **kwargs: Any):
return ureg.parse_expression(self._eq, value=value, **kwargs)
@dataclass(frozen=True)
class Relation:
bidirectional: True
src: ParserHelper
dst: ParserHelper
tranformation: Callable[..., Quantity[Any]]
@dataclass(frozen=True)
class ContextDefinition:
"""Definition of a Context
@context[(defaults)] <canonical name> [= <alias>] [= <alias>]
# units can be redefined within the context
<redefined unit> = <relation to another unit>
# can establish unidirectional relationships between dimensions
<dimension 1> -> <dimension 2>: <transformation function>
# can establish bidirectionl relationships between dimensions
<dimension 3> <-> <dimension 4>: <transformation function>
@end
Example::
@context(n=1) spectroscopy = sp
# n index of refraction of the medium.
[length] <-> [frequency]: speed_of_light / n / value
[frequency] -> [energy]: planck_constant * value
[energy] -> [frequency]: value / planck_constant
# allow wavenumber / kayser
[wavenumber] <-> [length]: 1 / value
@end
"""
name: str
aliases: Tuple[str, ...]
variables: Tuple[str, ...]
defaults: Dict[str, numbers.Number]
# Each element indicates: line number, is_bidirectional, src, dst, transformation func
relations: Tuple[Tuple[int, Relation], ...]
redefinitions: Tuple[Tuple[int, UnitDefinition], ...]
@staticmethod
def parse_definition(line, non_int_type) -> UnitDefinition:
definition = Definition.from_string(line, non_int_type)
if not isinstance(definition, UnitDefinition):
raise DefinitionSyntaxError(
"Expected <unit> = <converter>; got %s" % line.strip()
)
if definition.symbol != definition.name or definition.aliases:
raise DefinitionSyntaxError(
"Can't change a unit's symbol or aliases within a context"
)
if definition.is_base:
raise DefinitionSyntaxError("Can't define plain units within a context")
return definition
@classmethod
def from_lines(cls, lines, non_int_type=float) -> ContextDefinition:
lines = SourceIterator(lines)
lineno, header = next(lines)
try:
r = _header_re.search(header)
name = r.groupdict()["name"].strip()
aliases = r.groupdict()["aliases"]
if aliases:
aliases = tuple(a.strip() for a in r.groupdict()["aliases"].split("="))
else:
aliases = ()
defaults = r.groupdict()["defaults"]
except Exception as exc:
raise DefinitionSyntaxError(
"Could not parse the Context header '%s'" % header, lineno=lineno
) from exc
if defaults:
def to_num(val):
val = complex(val)
if not val.imag:
return val.real
return val
txt = defaults
try:
defaults = (part.split("=") for part in defaults.strip("()").split(","))
defaults = {str(k).strip(): to_num(v) for k, v in defaults}
except (ValueError, TypeError) as exc:
raise DefinitionSyntaxError(
f"Could not parse Context definition defaults: '{txt}'",
lineno=lineno,
) from exc
else:
defaults = {}
variables = set()
redefitions = []
relations = []
for lineno, line in lines:
try:
if "=" in line:
definition = cls.parse_definition(line, non_int_type)
redefitions.append((lineno, definition))
elif ":" in line:
rel, eq = line.split(":")
variables.update(_varname_re.findall(eq))
func = Expression(eq)
bidir = True
parts = rel.split("<->")
if len(parts) != 2:
bidir = False
parts = rel.split("->")
if len(parts) != 2:
raise Exception
src, dst = (
ParserHelper.from_string(s, non_int_type) for s in parts
)
relation = Relation(bidir, src, dst, func)
relations.append((lineno, relation))
else:
raise Exception
except Exception as exc:
raise DefinitionSyntaxError(
"Could not parse Context %s relation '%s': %s" % (name, line, exc),
lineno=lineno,
) from exc
if defaults:
missing_pars = defaults.keys() - set(variables)
if missing_pars:
raise DefinitionSyntaxError(
f"Context parameters {missing_pars} not found in any equation"
)
return cls(
name,
aliases,
tuple(variables),
defaults,
tuple(relations),
tuple(redefitions),
)
|
