# module pyparsing.py
#
# Copyright (c) 2003-2019 Paul T. McGuire
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
# CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
# TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# flake8: noqa
from pyparsing import (
Literal,
Word,
Group,
Forward,
alphas,
alphanums,
Regex,
CaselessKeyword,
Suppress,
delimitedList,
)
import math
import operator
# map operator symbols to corresponding arithmetic operations
epsilon = 1e-12
opn = {
"+": operator.add,
"-": operator.sub,
"*": operator.mul,
"/": operator.truediv,
"^": operator.pow,
}
fn = {
"sin": math.sin,
"cos": math.cos,
"tan": math.tan,
"exp": math.exp,
"abs": abs,
"trunc": lambda a: int(a),
"round": round,
"sgn": lambda a: -1 if a < -epsilon else 1 if a > epsilon else 0,
}
exprStack = []
[docs]def push_first(toks):
exprStack.append(toks[0])
[docs]def push_unary_minus(toks):
for t in toks:
if t == "-":
exprStack.append("unary -")
else:
break
[docs]def BNF():
"""
expop :: '^'
multop :: '*' | '/'
addop :: '+' | '-'
integer :: ['+' | '-'] '0'..'9'+
atom :: PI | E | real | fn '(' expr ')' | '(' expr ')'
factor :: atom [ expop factor ]*
term :: factor [ multop factor ]*
expr :: term [ addop term ]*
"""
# use CaselessKeyword for e and pi, to avoid accidentally matching
# functions that start with 'e' or 'pi' (such as 'exp'); Keyword
# and CaselessKeyword only match whole words
e = CaselessKeyword("E")
pi = CaselessKeyword("PI")
# fnumber = Combine(Word("+-"+nums, nums) +
# Optional("." + Optional(Word(nums))) +
# Optional(e + Word("+-"+nums, nums)))
# or use provided pyparsing_common.number, but convert back to str:
# fnumber = ppc.number().addParseAction(lambda t: str(t[0]))
fnumber = Regex(r"[+-]?\d+(?:\.\d*)?(?:[eE][+-]?\d+)?")
ident = Word(alphas, alphanums + "_$")
plus, minus, mult, div = map(Literal, "+-*/")
lpar, rpar = map(Suppress, "()")
addop = plus | minus
multop = mult | div
expop = Literal("^")
expr = Forward()
expr_list = delimitedList(Group(expr))
# add parse action that replaces the function identifier with a (name, number of args) tuple
fn_call = (ident + lpar - Group(expr_list) + rpar).setParseAction(
lambda t: t.insert(0, (t.pop(0), len(t[0])))
)
atom = (
addop[...]
+ (
(fn_call | pi | e | fnumber | ident).setParseAction(push_first)
| Group(lpar + expr + rpar)
)
).setParseAction(push_unary_minus)
# by defining exponentiation as "atom [ ^ factor ]..." instead of "atom [ ^ atom ]...", we get right-to-left
# exponents, instead of left-to-right that is, 2^3^2 = 2^(3^2), not (2^3)^2.
factor = Forward()
factor <<= atom + (expop + factor).setParseAction(push_first)[...]
term = factor + (multop + factor).setParseAction(push_first)[...]
expr <<= term + (addop + term).setParseAction(push_first)[...]
bnf = expr
return bnf
[docs]def evaluate_stack(s, stats):
op, num_args = s.pop(), 0
if isinstance(op, tuple):
op, num_args = op
if op == "unary -":
return -evaluate_stack(s, stats)
if op in "+-*/^":
# note: operands are pushed onto the stack in reverse order
op2 = evaluate_stack(s, stats)
op1 = evaluate_stack(s, stats)
return opn[op](op1, op2)
elif op == "PI":
return math.pi # 3.1415926535
elif op == "E":
return math.e # 2.718281828
elif op == "mean":
return stats['mean']
elif op == "min":
return stats['min']
elif op == "max":
return stats['max']
elif op == "std":
return stats['std']
elif op in fn:
# note: args are pushed onto the stack in reverse order
args = reversed([evaluate_stack(s, stats) for _ in range(num_args)])
return fn[op](*args)
elif op[0].isalpha():
raise Exception("invalid identifier '%s'" % op)
else:
return float(op)
[docs]def eval_fx(fx, stats):
"""Given fx and stats ('min', 'max', 'mean', 'std') return the result"""
_ = BNF().parseString(fx, parseAll=True)
val = evaluate_stack(exprStack[:], stats)
return val