Mini Shell
"""
babel.numbers
~~~~~~~~~~~~~
CLDR Plural support. See UTS #35.
:copyright: (c) 2013-2023 by the Babel Team.
:license: BSD, see LICENSE for more details.
"""
from __future__ import annotations
import decimal
import re
from collections.abc import Iterable, Mapping
from typing import TYPE_CHECKING, Any, Callable
if TYPE_CHECKING:
from typing_extensions import Literal
_plural_tags = ('zero', 'one', 'two', 'few', 'many', 'other')
_fallback_tag = 'other'
def extract_operands(source: float | decimal.Decimal) -> tuple[decimal.Decimal | int, int, int, int, int, int, Literal[0], Literal[0]]:
"""Extract operands from a decimal, a float or an int, according to `CLDR rules`_.
The result is a 8-tuple (n, i, v, w, f, t, c, e), where those symbols are as follows:
====== ===============================================================
Symbol Value
------ ---------------------------------------------------------------
n absolute value of the source number (integer and decimals).
i integer digits of n.
v number of visible fraction digits in n, with trailing zeros.
w number of visible fraction digits in n, without trailing zeros.
f visible fractional digits in n, with trailing zeros.
t visible fractional digits in n, without trailing zeros.
c compact decimal exponent value: exponent of the power of 10 used in compact decimal formatting.
e currently, synonym for ‘c’. however, may be redefined in the future.
====== ===============================================================
.. _`CLDR rules`: https://www.unicode.org/reports/tr35/tr35-61/tr35-numbers.html#Operands
:param source: A real number
:type source: int|float|decimal.Decimal
:return: A n-i-v-w-f-t-c-e tuple
:rtype: tuple[decimal.Decimal, int, int, int, int, int, int, int]
"""
n = abs(source)
i = int(n)
if isinstance(n, float):
if i == n:
n = i
else:
# Cast the `float` to a number via the string representation.
# This is required for Python 2.6 anyway (it will straight out fail to
# do the conversion otherwise), and it's highly unlikely that the user
# actually wants the lossless conversion behavior (quoting the Python
# documentation):
# > If value is a float, the binary floating point value is losslessly
# > converted to its exact decimal equivalent.
# > This conversion can often require 53 or more digits of precision.
# Should the user want that behavior, they can simply pass in a pre-
# converted `Decimal` instance of desired accuracy.
n = decimal.Decimal(str(n))
if isinstance(n, decimal.Decimal):
dec_tuple = n.as_tuple()
exp = dec_tuple.exponent
fraction_digits = dec_tuple.digits[exp:] if exp < 0 else ()
trailing = ''.join(str(d) for d in fraction_digits)
no_trailing = trailing.rstrip('0')
v = len(trailing)
w = len(no_trailing)
f = int(trailing or 0)
t = int(no_trailing or 0)
else:
v = w = f = t = 0
c = e = 0 # TODO: c and e are not supported
return n, i, v, w, f, t, c, e
class PluralRule:
"""Represents a set of language pluralization rules. The constructor
accepts a list of (tag, expr) tuples or a dict of `CLDR rules`_. The
resulting object is callable and accepts one parameter with a positive or
negative number (both integer and float) for the number that indicates the
plural form for a string and returns the tag for the format:
>>> rule = PluralRule({'one': 'n is 1'})
>>> rule(1)
'one'
>>> rule(2)
'other'
Currently the CLDR defines these tags: zero, one, two, few, many and
other where other is an implicit default. Rules should be mutually
exclusive; for a given numeric value, only one rule should apply (i.e.
the condition should only be true for one of the plural rule elements.
.. _`CLDR rules`: https://www.unicode.org/reports/tr35/tr35-33/tr35-numbers.html#Language_Plural_Rules
"""
__slots__ = ('abstract', '_func')
def __init__(self, rules: Mapping[str, str] | Iterable[tuple[str, str]]) -> None:
"""Initialize the rule instance.
:param rules: a list of ``(tag, expr)``) tuples with the rules
conforming to UTS #35 or a dict with the tags as keys
and expressions as values.
:raise RuleError: if the expression is malformed
"""
if isinstance(rules, Mapping):
rules = rules.items()
found = set()
self.abstract: list[tuple[str, Any]] = []
for key, expr in sorted(rules):
if key not in _plural_tags:
raise ValueError(f"unknown tag {key!r}")
elif key in found:
raise ValueError(f"tag {key!r} defined twice")
found.add(key)
ast = _Parser(expr).ast
if ast:
self.abstract.append((key, ast))
def __repr__(self) -> str:
rules = self.rules
args = ", ".join([f"{tag}: {rules[tag]}" for tag in _plural_tags if tag in rules])
return f"<{type(self).__name__} {args!r}>"
@classmethod
def parse(cls, rules: Mapping[str, str] | Iterable[tuple[str, str]] | PluralRule) -> PluralRule:
"""Create a `PluralRule` instance for the given rules. If the rules
are a `PluralRule` object, that object is returned.
:param rules: the rules as list or dict, or a `PluralRule` object
:raise RuleError: if the expression is malformed
"""
if isinstance(rules, PluralRule):
return rules
return cls(rules)
@property
def rules(self) -> Mapping[str, str]:
"""The `PluralRule` as a dict of unicode plural rules.
>>> rule = PluralRule({'one': 'n is 1'})
>>> rule.rules
{'one': 'n is 1'}
"""
_compile = _UnicodeCompiler().compile
return {tag: _compile(ast) for tag, ast in self.abstract}
@property
def tags(self) -> frozenset[str]:
"""A set of explicitly defined tags in this rule. The implicit default
``'other'`` rules is not part of this set unless there is an explicit
rule for it.
"""
return frozenset(i[0] for i in self.abstract)
def __getstate__(self) -> list[tuple[str, Any]]:
return self.abstract
def __setstate__(self, abstract: list[tuple[str, Any]]) -> None:
self.abstract = abstract
def __call__(self, n: float | decimal.Decimal) -> str:
if not hasattr(self, '_func'):
self._func = to_python(self)
return self._func(n)
def to_javascript(rule: Mapping[str, str] | Iterable[tuple[str, str]] | PluralRule) -> str:
"""Convert a list/dict of rules or a `PluralRule` object into a JavaScript
function. This function depends on no external library:
>>> to_javascript({'one': 'n is 1'})
"(function(n) { return (n == 1) ? 'one' : 'other'; })"
Implementation detail: The function generated will probably evaluate
expressions involved into range operations multiple times. This has the
advantage that external helper functions are not required and is not a
big performance hit for these simple calculations.
:param rule: the rules as list or dict, or a `PluralRule` object
:raise RuleError: if the expression is malformed
"""
to_js = _JavaScriptCompiler().compile
result = ['(function(n) { return ']
for tag, ast in PluralRule.parse(rule).abstract:
result.append(f"{to_js(ast)} ? {tag!r} : ")
result.append('%r; })' % _fallback_tag)
return ''.join(result)
def to_python(rule: Mapping[str, str] | Iterable[tuple[str, str]] | PluralRule) -> Callable[[float | decimal.Decimal], str]:
"""Convert a list/dict of rules or a `PluralRule` object into a regular
Python function. This is useful in situations where you need a real
function and don't are about the actual rule object:
>>> func = to_python({'one': 'n is 1', 'few': 'n in 2..4'})
>>> func(1)
'one'
>>> func(3)
'few'
>>> func = to_python({'one': 'n in 1,11', 'few': 'n in 3..10,13..19'})
>>> func(11)
'one'
>>> func(15)
'few'
:param rule: the rules as list or dict, or a `PluralRule` object
:raise RuleError: if the expression is malformed
"""
namespace = {
'IN': in_range_list,
'WITHIN': within_range_list,
'MOD': cldr_modulo,
'extract_operands': extract_operands,
}
to_python_func = _PythonCompiler().compile
result = [
'def evaluate(n):',
' n, i, v, w, f, t, c, e = extract_operands(n)',
]
for tag, ast in PluralRule.parse(rule).abstract:
# the str() call is to coerce the tag to the native string. It's
# a limited ascii restricted set of tags anyways so that is fine.
result.append(f" if ({to_python_func(ast)}): return {str(tag)!r}")
result.append(f" return {_fallback_tag!r}")
code = compile('\n'.join(result), '<rule>', 'exec')
eval(code, namespace)
return namespace['evaluate']
def to_gettext(rule: Mapping[str, str] | Iterable[tuple[str, str]] | PluralRule) -> str:
"""The plural rule as gettext expression. The gettext expression is
technically limited to integers and returns indices rather than tags.
>>> to_gettext({'one': 'n is 1', 'two': 'n is 2'})
'nplurals=3; plural=((n == 1) ? 0 : (n == 2) ? 1 : 2);'
:param rule: the rules as list or dict, or a `PluralRule` object
:raise RuleError: if the expression is malformed
"""
rule = PluralRule.parse(rule)
used_tags = rule.tags | {_fallback_tag}
_compile = _GettextCompiler().compile
_get_index = [tag for tag in _plural_tags if tag in used_tags].index
result = [f"nplurals={len(used_tags)}; plural=("]
for tag, ast in rule.abstract:
result.append(f"{_compile(ast)} ? {_get_index(tag)} : ")
result.append(f"{_get_index(_fallback_tag)});")
return ''.join(result)
def in_range_list(num: float | decimal.Decimal, range_list: Iterable[Iterable[float | decimal.Decimal]]) -> bool:
"""Integer range list test. This is the callback for the "in" operator
of the UTS #35 pluralization rule language:
>>> in_range_list(1, [(1, 3)])
True
>>> in_range_list(3, [(1, 3)])
True
>>> in_range_list(3, [(1, 3), (5, 8)])
True
>>> in_range_list(1.2, [(1, 4)])
False
>>> in_range_list(10, [(1, 4)])
False
>>> in_range_list(10, [(1, 4), (6, 8)])
False
"""
return num == int(num) and within_range_list(num, range_list)
def within_range_list(num: float | decimal.Decimal, range_list: Iterable[Iterable[float | decimal.Decimal]]) -> bool:
"""Float range test. This is the callback for the "within" operator
of the UTS #35 pluralization rule language:
>>> within_range_list(1, [(1, 3)])
True
>>> within_range_list(1.0, [(1, 3)])
True
>>> within_range_list(1.2, [(1, 4)])
True
>>> within_range_list(8.8, [(1, 4), (7, 15)])
True
>>> within_range_list(10, [(1, 4)])
False
>>> within_range_list(10.5, [(1, 4), (20, 30)])
False
"""
return any(num >= min_ and num <= max_ for min_, max_ in range_list)
def cldr_modulo(a: float, b: float) -> float:
"""Javaish modulo. This modulo operator returns the value with the sign
of the dividend rather than the divisor like Python does:
>>> cldr_modulo(-3, 5)
-3
>>> cldr_modulo(-3, -5)
-3
>>> cldr_modulo(3, 5)
3
"""
reverse = 0
if a < 0:
a *= -1
reverse = 1
if b < 0:
b *= -1
rv = a % b
if reverse:
rv *= -1
return rv
class RuleError(Exception):
"""Raised if a rule is malformed."""
_VARS = {
'n', # absolute value of the source number.
'i', # integer digits of n.
'v', # number of visible fraction digits in n, with trailing zeros.*
'w', # number of visible fraction digits in n, without trailing zeros.*
'f', # visible fraction digits in n, with trailing zeros.*
't', # visible fraction digits in n, without trailing zeros.*
'c', # compact decimal exponent value: exponent of the power of 10 used in compact decimal formatting.
'e', # currently, synonym for `c`. however, may be redefined in the future.
}
_RULES: list[tuple[str | None, re.Pattern[str]]] = [
(None, re.compile(r'\s+', re.UNICODE)),
('word', re.compile(fr'\b(and|or|is|(?:with)?in|not|mod|[{"".join(_VARS)}])\b')),
('value', re.compile(r'\d+')),
('symbol', re.compile(r'%|,|!=|=')),
('ellipsis', re.compile(r'\.{2,3}|\u2026', re.UNICODE)) # U+2026: ELLIPSIS
]
def tokenize_rule(s: str) -> list[tuple[str, str]]:
s = s.split('@')[0]
result: list[tuple[str, str]] = []
pos = 0
end = len(s)
while pos < end:
for tok, rule in _RULES:
match = rule.match(s, pos)
if match is not None:
pos = match.end()
if tok:
result.append((tok, match.group()))
break
else:
raise RuleError('malformed CLDR pluralization rule. '
'Got unexpected %r' % s[pos])
return result[::-1]
def test_next_token(
tokens: list[tuple[str, str]],
type_: str,
value: str | None = None,
) -> list[tuple[str, str]] | bool:
return tokens and tokens[-1][0] == type_ and \
(value is None or tokens[-1][1] == value)
def skip_token(tokens: list[tuple[str, str]], type_: str, value: str | None = None):
if test_next_token(tokens, type_, value):
return tokens.pop()
def value_node(value: int) -> tuple[Literal['value'], tuple[int]]:
return 'value', (value, )
def ident_node(name: str) -> tuple[str, tuple[()]]:
return name, ()
def range_list_node(
range_list: Iterable[Iterable[float | decimal.Decimal]],
) -> tuple[Literal['range_list'], Iterable[Iterable[float | decimal.Decimal]]]:
return 'range_list', range_list
def negate(rv: tuple[Any, ...]) -> tuple[Literal['not'], tuple[tuple[Any, ...]]]:
return 'not', (rv,)
class _Parser:
"""Internal parser. This class can translate a single rule into an abstract
tree of tuples. It implements the following grammar::
condition = and_condition ('or' and_condition)*
('@integer' samples)?
('@decimal' samples)?
and_condition = relation ('and' relation)*
relation = is_relation | in_relation | within_relation
is_relation = expr 'is' ('not')? value
in_relation = expr (('not')? 'in' | '=' | '!=') range_list
within_relation = expr ('not')? 'within' range_list
expr = operand (('mod' | '%') value)?
operand = 'n' | 'i' | 'f' | 't' | 'v' | 'w'
range_list = (range | value) (',' range_list)*
value = digit+
digit = 0|1|2|3|4|5|6|7|8|9
range = value'..'value
samples = sampleRange (',' sampleRange)* (',' ('…'|'...'))?
sampleRange = decimalValue '~' decimalValue
decimalValue = value ('.' value)?
- Whitespace can occur between or around any of the above tokens.
- Rules should be mutually exclusive; for a given numeric value, only one
rule should apply (i.e. the condition should only be true for one of
the plural rule elements).
- The in and within relations can take comma-separated lists, such as:
'n in 3,5,7..15'.
- Samples are ignored.
The translator parses the expression on instantiation into an attribute
called `ast`.
"""
def __init__(self, string):
self.tokens = tokenize_rule(string)
if not self.tokens:
# If the pattern is only samples, it's entirely possible
# no stream of tokens whatsoever is generated.
self.ast = None
return
self.ast = self.condition()
if self.tokens:
raise RuleError(f"Expected end of rule, got {self.tokens[-1][1]!r}")
def expect(self, type_, value=None, term=None):
token = skip_token(self.tokens, type_, value)
if token is not None:
return token
if term is None:
term = repr(value is None and type_ or value)
if not self.tokens:
raise RuleError(f"expected {term} but end of rule reached")
raise RuleError(f"expected {term} but got {self.tokens[-1][1]!r}")
def condition(self):
op = self.and_condition()
while skip_token(self.tokens, 'word', 'or'):
op = 'or', (op, self.and_condition())
return op
def and_condition(self):
op = self.relation()
while skip_token(self.tokens, 'word', 'and'):
op = 'and', (op, self.relation())
return op
def relation(self):
left = self.expr()
if skip_token(self.tokens, 'word', 'is'):
return skip_token(self.tokens, 'word', 'not') and 'isnot' or 'is', \
(left, self.value())
negated = skip_token(self.tokens, 'word', 'not')
method = 'in'
if skip_token(self.tokens, 'word', 'within'):
method = 'within'
else:
if not skip_token(self.tokens, 'word', 'in'):
if negated:
raise RuleError('Cannot negate operator based rules.')
return self.newfangled_relation(left)
rv = 'relation', (method, left, self.range_list())
return negate(rv) if negated else rv
def newfangled_relation(self, left):
if skip_token(self.tokens, 'symbol', '='):
negated = False
elif skip_token(self.tokens, 'symbol', '!='):
negated = True
else:
raise RuleError('Expected "=" or "!=" or legacy relation')
rv = 'relation', ('in', left, self.range_list())
return negate(rv) if negated else rv
def range_or_value(self):
left = self.value()
if skip_token(self.tokens, 'ellipsis'):
return left, self.value()
else:
return left, left
def range_list(self):
range_list = [self.range_or_value()]
while skip_token(self.tokens, 'symbol', ','):
range_list.append(self.range_or_value())
return range_list_node(range_list)
def expr(self):
word = skip_token(self.tokens, 'word')
if word is None or word[1] not in _VARS:
raise RuleError('Expected identifier variable')
name = word[1]
if skip_token(self.tokens, 'word', 'mod'):
return 'mod', ((name, ()), self.value())
elif skip_token(self.tokens, 'symbol', '%'):
return 'mod', ((name, ()), self.value())
return ident_node(name)
def value(self):
return value_node(int(self.expect('value')[1]))
def _binary_compiler(tmpl):
"""Compiler factory for the `_Compiler`."""
return lambda self, left, right: tmpl % (self.compile(left), self.compile(right))
def _unary_compiler(tmpl):
"""Compiler factory for the `_Compiler`."""
return lambda self, x: tmpl % self.compile(x)
compile_zero = lambda x: '0'
class _Compiler:
"""The compilers are able to transform the expressions into multiple
output formats.
"""
def compile(self, arg):
op, args = arg
return getattr(self, f"compile_{op}")(*args)
compile_n = lambda x: 'n'
compile_i = lambda x: 'i'
compile_v = lambda x: 'v'
compile_w = lambda x: 'w'
compile_f = lambda x: 'f'
compile_t = lambda x: 't'
compile_c = lambda x: 'c'
compile_e = lambda x: 'e'
compile_value = lambda x, v: str(v)
compile_and = _binary_compiler('(%s && %s)')
compile_or = _binary_compiler('(%s || %s)')
compile_not = _unary_compiler('(!%s)')
compile_mod = _binary_compiler('(%s %% %s)')
compile_is = _binary_compiler('(%s == %s)')
compile_isnot = _binary_compiler('(%s != %s)')
def compile_relation(self, method, expr, range_list):
raise NotImplementedError()
class _PythonCompiler(_Compiler):
"""Compiles an expression to Python."""
compile_and = _binary_compiler('(%s and %s)')
compile_or = _binary_compiler('(%s or %s)')
compile_not = _unary_compiler('(not %s)')
compile_mod = _binary_compiler('MOD(%s, %s)')
def compile_relation(self, method, expr, range_list):
ranges = ",".join([f"({self.compile(a)}, {self.compile(b)})" for (a, b) in range_list[1]])
return f"{method.upper()}({self.compile(expr)}, [{ranges}])"
class _GettextCompiler(_Compiler):
"""Compile into a gettext plural expression."""
compile_i = _Compiler.compile_n
compile_v = compile_zero
compile_w = compile_zero
compile_f = compile_zero
compile_t = compile_zero
def compile_relation(self, method, expr, range_list):
rv = []
expr = self.compile(expr)
for item in range_list[1]:
if item[0] == item[1]:
rv.append(f"({expr} == {self.compile(item[0])})")
else:
min, max = map(self.compile, item)
rv.append(f"({expr} >= {min} && {expr} <= {max})")
return f"({' || '.join(rv)})"
class _JavaScriptCompiler(_GettextCompiler):
"""Compiles the expression to plain of JavaScript."""
# XXX: presently javascript does not support any of the
# fraction support and basically only deals with integers.
compile_i = lambda x: 'parseInt(n, 10)'
compile_v = compile_zero
compile_w = compile_zero
compile_f = compile_zero
compile_t = compile_zero
def compile_relation(self, method, expr, range_list):
code = _GettextCompiler.compile_relation(
self, method, expr, range_list)
if method == 'in':
expr = self.compile(expr)
code = f"(parseInt({expr}, 10) == {expr} && {code})"
return code
class _UnicodeCompiler(_Compiler):
"""Returns a unicode pluralization rule again."""
# XXX: this currently spits out the old syntax instead of the new
# one. We can change that, but it will break a whole bunch of stuff
# for users I suppose.
compile_is = _binary_compiler('%s is %s')
compile_isnot = _binary_compiler('%s is not %s')
compile_and = _binary_compiler('%s and %s')
compile_or = _binary_compiler('%s or %s')
compile_mod = _binary_compiler('%s mod %s')
def compile_not(self, relation):
return self.compile_relation(*relation[1], negated=True)
def compile_relation(self, method, expr, range_list, negated=False):
ranges = []
for item in range_list[1]:
if item[0] == item[1]:
ranges.append(self.compile(item[0]))
else:
ranges.append(f"{self.compile(item[0])}..{self.compile(item[1])}")
return f"{self.compile(expr)}{' not' if negated else ''} {method} {','.join(ranges)}"
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