Spaces:
Runtime error
Runtime error
File size: 9,159 Bytes
96ee597 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 |
"""Copyright 2020 Mobvoi Inc. (authors: Fangjun Kuang)
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
Copyright PolyAI Limited.
"""
from dataclasses import dataclass, field
from typing import Dict, Generic, List, Optional, TypeVar, Union
Symbol = TypeVar('Symbol')
# Disable __repr__ otherwise it could freeze e.g. Jupyter.
@dataclass(repr=False)
class SymbolTable(Generic[Symbol]):
'''SymbolTable that maps symbol IDs, found on the FSA arcs to
actual objects. These objects can be arbitrary Python objects
that can serve as keys in a dictionary (i.e. they need to be
hashable and immutable).
The SymbolTable can only be read to/written from disk if the
symbols are strings.
'''
_id2sym: Dict[int, Symbol] = field(default_factory=dict)
'''Map an integer to a symbol.
'''
_sym2id: Dict[Symbol, int] = field(default_factory=dict)
'''Map a symbol to an integer.
'''
_next_available_id: int = 1
'''A helper internal field that helps adding new symbols
to the table efficiently.
'''
eps: Symbol = '<eps>'
'''Null symbol, always mapped to index 0.
'''
def __post_init__(self):
for idx, sym in self._id2sym.items():
assert self._sym2id[sym] == idx
assert idx >= 0
for sym, idx in self._sym2id.items():
assert idx >= 0
assert self._id2sym[idx] == sym
if 0 not in self._id2sym:
self._id2sym[0] = self.eps
self._sym2id[self.eps] = 0
else:
assert self._id2sym[0] == self.eps
assert self._sym2id[self.eps] == 0
self._next_available_id = max(self._id2sym) + 1
@staticmethod
def from_str(s: str) -> 'SymbolTable':
'''Build a symbol table from a string.
The string consists of lines. Every line has two fields separated
by space(s), tab(s) or both. The first field is the symbol and the
second the integer id of the symbol.
Args:
s:
The input string with the format described above.
Returns:
An instance of :class:`SymbolTable`.
'''
id2sym: Dict[int, str] = dict()
sym2id: Dict[str, int] = dict()
for line in s.split('\n'):
fields = line.split()
if len(fields) == 0:
continue # skip empty lines
assert len(fields) == 2, \
f'Expect a line with 2 fields. Given: {len(fields)}'
sym, idx = fields[0], int(fields[1])
assert sym not in sym2id, f'Duplicated symbol {sym}'
assert idx not in id2sym, f'Duplicated id {idx}'
id2sym[idx] = sym
sym2id[sym] = idx
eps = id2sym.get(0, '<eps>')
return SymbolTable(_id2sym=id2sym, _sym2id=sym2id, eps=eps)
@staticmethod
def from_file(filename: str) -> 'SymbolTable':
'''Build a symbol table from file.
Every line in the symbol table file has two fields separated by
space(s), tab(s) or both. The following is an example file:
.. code-block::
<eps> 0
a 1
b 2
c 3
Args:
filename:
Name of the symbol table file. Its format is documented above.
Returns:
An instance of :class:`SymbolTable`.
'''
with open(filename, 'r', encoding='utf-8') as f:
return SymbolTable.from_str(f.read().strip())
def to_str(self) -> str:
'''
Returns:
Return a string representation of this object. You can pass
it to the method ``from_str`` to recreate an identical object.
'''
s = ''
for idx, symbol in sorted(self._id2sym.items()):
s += f'{symbol} {idx}\n'
return s
def to_file(self, filename: str):
'''Serialize the SymbolTable to a file.
Every line in the symbol table file has two fields separated by
space(s), tab(s) or both. The following is an example file:
.. code-block::
<eps> 0
a 1
b 2
c 3
Args:
filename:
Name of the symbol table file. Its format is documented above.
'''
with open(filename, 'w') as f:
for idx, symbol in sorted(self._id2sym.items()):
print(symbol, idx, file=f)
def add(self, symbol: Symbol, index: Optional[int] = None) -> int:
'''Add a new symbol to the SymbolTable.
Args:
symbol:
The symbol to be added.
index:
Optional int id to which the symbol should be assigned.
If it is not available, a ValueError will be raised.
Returns:
The int id to which the symbol has been assigned.
'''
# Already in the table? Return its ID.
if symbol in self._sym2id:
return self._sym2id[symbol]
# Specific ID not provided - use next available.
if index is None:
index = self._next_available_id
# Specific ID provided but not available.
if index in self._id2sym:
raise ValueError(f"Cannot assign id '{index}' to '{symbol}' - "
f"already occupied by {self._id2sym[index]}")
self._sym2id[symbol] = index
self._id2sym[index] = symbol
# Update next available ID if needed
if self._next_available_id <= index:
self._next_available_id = index + 1
return index
def get(self, k: Union[int, Symbol]) -> Union[Symbol, int]:
'''Get a symbol for an id or get an id for a symbol
Args:
k:
If it is an id, it tries to find the symbol corresponding
to the id; if it is a symbol, it tries to find the id
corresponding to the symbol.
Returns:
An id or a symbol depending on the given `k`.
'''
if isinstance(k, int):
return self._id2sym[k]
else:
return self._sym2id[k]
def merge(self, other: 'SymbolTable') -> 'SymbolTable':
'''Create a union of two SymbolTables.
Raises an AssertionError if the same IDs are occupied by
different symbols.
Args:
other:
A symbol table to merge with ``self``.
Returns:
A new symbol table.
'''
self._check_compatible(other)
id2sym = {**self._id2sym, **other._id2sym}
sym2id = {**self._sym2id, **other._sym2id}
return SymbolTable(_id2sym=id2sym, _sym2id=sym2id, eps=self.eps)
def _check_compatible(self, other: 'SymbolTable') -> None:
# Epsilon compatibility
assert self.eps == other.eps, f'Mismatched epsilon symbol: ' \
f'{self.eps} != {other.eps}'
# IDs compatibility
common_ids = set(self._id2sym).intersection(other._id2sym)
for idx in common_ids:
assert self[idx] == other[idx], f'ID conflict for id: {idx}, ' \
f'self[idx] = "{self[idx]}", ' \
f'other[idx] = "{other[idx]}"'
# Symbols compatibility
common_symbols = set(self._sym2id).intersection(other._sym2id)
for sym in common_symbols:
assert self[sym] == other[sym], f'ID conflict for id: {sym}, ' \
f'self[sym] = "{self[sym]}", ' \
f'other[sym] = "{other[sym]}"'
def __getitem__(self, item: Union[int, Symbol]) -> Union[Symbol, int]:
return self.get(item)
def __contains__(self, item: Union[int, Symbol]) -> bool:
if isinstance(item, int):
return item in self._id2sym
else:
return item in self._sym2id
def __len__(self) -> int:
return len(self._id2sym)
def __eq__(self, other: 'SymbolTable') -> bool:
if len(self) != len(other):
return False
for s in self.symbols:
if self[s] != other[s]:
return False
return True
@property
def ids(self) -> List[int]:
'''Returns a list of integer IDs corresponding to the symbols.
'''
ans = list(self._id2sym.keys())
ans.sort()
return ans
@property
def symbols(self) -> List[Symbol]:
'''Returns a list of symbols (e.g., strings) corresponding to
the integer IDs.
'''
ans = list(self._sym2id.keys())
ans.sort()
return ans
|