# Licensed under a 3-clause BSD style license - see LICNSE.rst
# This module includes files automatically generated from ply (these end in
# _lextab.py and _parsetab.py). To generate these files, remove them from this
# folder, then build astropy and run the tests in-place:
#
# python setup.py build_ext --inplace
# pytest astropy/units
#
# You can then commit the changes to the re-generated _lextab.py and
# _parsetab.py files.
"""Handles the CDS string format for units."""
from __future__ import annotations
import re
from typing import TYPE_CHECKING
from astropy.units.utils import is_effectively_unity
from astropy.utils import classproperty, parsing
from astropy.utils.misc import did_you_mean
from .fits import FITS
from .generic import Generic
if TYPE_CHECKING:
from typing import ClassVar, Literal
import numpy as np
from astropy.extern.ply.lex import Lexer
from astropy.units import UnitBase
from astropy.utils.parsing import ThreadSafeParser
class CDS(FITS):
"""
Support the `Centre de Données astronomiques de Strasbourg
`_ `Standards for Astronomical
Catalogues 2.0 `_
format, and the `complete set of supported units
`_. This format is used
by VOTable up to version 1.2.
"""
_space: ClassVar[str] = "."
_times: ClassVar[str] = "x"
_scale_unit_separator: ClassVar[str] = ""
_tokens: ClassVar[tuple[str, ...]] = (
"PRODUCT",
"DIVISION",
"OPEN_PAREN",
"CLOSE_PAREN",
"OPEN_BRACKET",
"CLOSE_BRACKET",
"X",
"SIGN",
"UINT",
"UFLOAT",
"UNIT",
"DIMENSIONLESS",
)
@classproperty(lazy=True)
def _units(cls) -> dict[str, UnitBase]:
from astropy import units as u
from astropy.units import cds
return {k: v for k, v in cds.__dict__.items() if isinstance(v, u.UnitBase)}
@classproperty(lazy=True)
def _lexer(cls) -> Lexer:
tokens = cls._tokens
t_PRODUCT = r"\."
t_DIVISION = r"/"
t_OPEN_PAREN = r"\("
t_CLOSE_PAREN = r"\)"
t_OPEN_BRACKET = r"\["
t_CLOSE_BRACKET = r"\]"
# NOTE THE ORDERING OF THESE RULES IS IMPORTANT!!
# Regular expression rules for simple tokens
def t_UFLOAT(t):
r"((\d+\.?\d+)|(\.\d+))([eE][+-]?\d+)?"
if not re.search(r"[eE\.]", t.value):
t.type = "UINT"
t.value = int(t.value)
else:
t.value = float(t.value)
return t
def t_UINT(t):
r"\d+"
t.value = int(t.value)
return t
def t_SIGN(t):
r"[+-](?=\d)"
t.value = float(t.value + "1")
return t
def t_X(t): # multiplication for factor in front of unit
r"[x×]"
return t
# Most units are just combinations of letters with no numbers, but there
# are a few special ones (\h is Planch constant) and three that end in 0.
def t_UNIT(t):
r"%|°|\\h|(a|eps|mu)0|((?!\d)\w)+"
t.value = cls._get_unit(t)
return t
def t_DIMENSIONLESS(t):
r"---|-"
# These are separate from t_UNIT since they cannot have a prefactor.
t.value = cls._get_unit(t)
return t
t_ignore = ""
# Error handling rule
def t_error(t):
raise ValueError(f"Invalid character at col {t.lexpos}")
return parsing.lex(
lextab="cds_lextab", package="astropy/units", reflags=int(re.UNICODE)
)
@classproperty(lazy=True)
def _parser(cls) -> ThreadSafeParser:
"""
The grammar here is based on the description in the `Standards
for Astronomical Catalogues 2.0
`_, which is not
terribly precise. The exact grammar is here is based on the
YACC grammar in the `unity library `_.
"""
tokens = cls._tokens
def p_main(p):
"""
main : factor combined_units
| combined_units
| DIMENSIONLESS
| OPEN_BRACKET combined_units CLOSE_BRACKET
| OPEN_BRACKET DIMENSIONLESS CLOSE_BRACKET
| factor
"""
from astropy.units import dex
from astropy.units.core import CompositeUnit, Unit
if len(p) == 3:
p[0] = CompositeUnit(p[1] * p[2].scale, p[2].bases, p[2].powers)
elif len(p) == 4:
p[0] = dex(p[2])
else:
p[0] = Unit(p[1])
def p_combined_units(p):
"""
combined_units : product_of_units
| division_of_units
"""
p[0] = p[1]
def p_product_of_units(p):
"""
product_of_units : unit_expression PRODUCT combined_units
| unit_expression
"""
if len(p) == 4:
p[0] = p[1] * p[3]
else:
p[0] = p[1]
def p_division_of_units(p):
"""
division_of_units : DIVISION unit_expression
| combined_units DIVISION unit_expression
"""
if len(p) == 3:
p[0] = p[2] ** -1
else:
p[0] = p[1] / p[3]
def p_unit_expression(p):
"""
unit_expression : unit_with_power
| OPEN_PAREN combined_units CLOSE_PAREN
"""
if len(p) == 2:
p[0] = p[1]
else:
p[0] = p[2]
def p_factor(p):
"""
factor : signed_float X UINT signed_int
| UINT X UINT signed_int
| UINT signed_int
| UINT
| signed_float
"""
if len(p) == 5:
if p[3] != 10:
raise ValueError("Only base ten exponents are allowed in CDS")
p[0] = p[1] * 10.0 ** p[4]
elif len(p) == 3:
if p[1] != 10:
raise ValueError("Only base ten exponents are allowed in CDS")
p[0] = 10.0 ** p[2]
elif len(p) == 2:
p[0] = p[1]
def p_unit_with_power(p):
"""
unit_with_power : UNIT numeric_power
| UNIT
"""
if len(p) == 2:
p[0] = p[1]
else:
p[0] = p[1] ** p[2]
def p_numeric_power(p):
"""
numeric_power : sign UINT
"""
p[0] = p[1] * p[2]
def p_sign(p):
"""
sign : SIGN
|
"""
if len(p) == 2:
p[0] = p[1]
else:
p[0] = 1.0
def p_signed_int(p):
"""
signed_int : SIGN UINT
"""
p[0] = p[1] * p[2]
def p_signed_float(p):
"""
signed_float : sign UINT
| sign UFLOAT
"""
p[0] = p[1] * p[2]
def p_error(p):
raise ValueError()
return parsing.yacc(tabmodule="cds_parsetab", package="astropy/units")
@classmethod
def _parse_unit(cls, unit: str, detailed_exception: bool = True) -> UnitBase:
if unit not in cls._units:
if detailed_exception:
raise ValueError(
f"Unit '{unit}' not supported by the CDS SAC standard. "
f"{did_you_mean(unit, cls._units)}"
)
else:
raise ValueError()
return cls._units[unit]
@classmethod
def parse(cls, s: str, debug: bool = False) -> UnitBase:
if " " in s:
raise ValueError("CDS unit must not contain whitespace")
if not isinstance(s, str):
s = s.decode("ascii")
return cls._do_parse(s, debug)
@classmethod
def _format_mantissa(cls, m: str) -> str:
return "" if m == "1" else m
@classmethod
def _format_superscript(cls, number: str) -> str:
return number if number.startswith("-") else "+" + number
@classmethod
def format_exponential_notation(
cls, val: float | np.number, format_spec: str = ".8g"
) -> str:
return super(Generic, cls).format_exponential_notation(val, format_spec)
@classmethod
def to_string(
cls, unit: UnitBase, fraction: bool | Literal["inline"] = False
) -> str:
# Remove units that aren't known to the format
unit = cls._decompose_to_known_units(unit)
if not unit.bases:
if unit.scale == 1:
return "---"
elif is_effectively_unity(unit.scale * 100.0):
return "%"
return cls._to_string(unit, fraction=fraction)