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"""
parsing utilities
"""
import token
from sympy import Basic, Float, Integer, Rational, Symbol, sqrt
from sympy.parsing.sympy_parser import auto_number, parse_expr, rationalize
from unyt._unit_lookup_table import inv_name_alternatives
from unyt.exceptions import UnitParseError
def _auto_positive_symbol(tokens, local_dict, global_dict):
"""
Inserts calls to ``Symbol`` for undefined variables.
Passes in positive=True as a keyword argument.
Adapted from sympy.sympy.parsing.sympy_parser.auto_symbol
"""
result = []
tokens.append((None, None)) # so zip traverses all tokens
for tok, nextTok in zip(tokens, tokens[1:]):
tokNum, tokVal = tok
nextTokNum, nextTokVal = nextTok
if tokNum == token.NAME:
name = tokVal
if name in global_dict:
obj = global_dict[name]
if isinstance(obj, (Basic, type)) or callable(obj):
result.append((token.NAME, name))
continue
# try to resolve known alternative unit name
try:
used_name = inv_name_alternatives[str(name)]
except KeyError:
# if we don't know this name it's a user-defined unit name
# so we should create a new symbol for it
used_name = str(name)
result.extend(
[
(token.NAME, "Symbol"),
(token.OP, "("),
(token.NAME, repr(used_name)),
(token.OP, ","),
(token.NAME, "positive"),
(token.OP, "="),
(token.NAME, "True"),
(token.OP, ")"),
]
)
else:
result.append((tokNum, tokVal))
return result
global_dict = {
"Symbol": Symbol,
"Integer": Integer,
"Float": Float,
"Rational": Rational,
"sqrt": sqrt,
}
unit_text_transform = (_auto_positive_symbol, auto_number, rationalize)
def parse_unyt_expr(unit_expr):
if not unit_expr:
# Bug catch...
# if unit_expr is an empty string, parse_expr fails hard...
unit_expr = "1"
# Avoid a parse error if someone uses the percent unit and the
# parser tries to interpret it as the modulo operator
unit_expr = unit_expr.replace("%", "percent")
unit_expr = unit_expr.replace("°", "deg")
try:
unit_expr = parse_expr(
unit_expr, global_dict=global_dict, transformations=unit_text_transform
)
except Exception as e:
msg = f"Unit expression '{unit_expr}' raised an error during parsing:\n{e!r}"
raise UnitParseError(msg)
return unit_expr
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