evaluate.py

import numpy as np

opn = {
    "+": np.add,
    "-": np.subtract,
    "*": np.multiply,
    "/": np.divide,
    "^": np.power,
    "==": np.equal,
    "!=": np.not_equal,
    ">=": np.greater_equal,
    "<=": np.less_equal,
    ">": np.greater,
    "<": np.less,
}


fn = {
    "sin": np.sin,
    "cos": np.cos,
    "log": np.log,
    "abs": np.abs,
    "clip": np.clip,
}


def evaluate_stack(s, arrays):
    op, num_args = s.pop(), 0
    if isinstance(op, tuple):
        op, num_args = op
    if op == "unary -":
        return -evaluate_stack(s, arrays)
    elif op == "NaN":
        return np.nan
    if op in "+-*/^":
        # note: operands are pushed onto the stack in reverse order
        op2 = evaluate_stack(s, arrays)
        op1 = evaluate_stack(s, arrays)
        return opn[op](op1, op2)
    if op == "==" or op == "!=" or op == ">=" or op == "<=" or op == ">" or op == "<":
        op2 = evaluate_stack(s, arrays)
        op1 = evaluate_stack(s, arrays)
        return opn[op](op1, op2)
    elif op in fn:
        # note: args are pushed onto the stack in reverse order
        args = reversed([evaluate_stack(s, arrays) for _ in range(num_args)])
        return fn[op](*args)
    else:
        return float(op)

def evaluate(expression, context_dict):
    exprStack[:] = []
    try:
        results = BNF().parseString(expression, parseAll=True)
        return evaluate_stack(exprStack[:], context_dict)
    except ParseException as pe:
        print(s, "failed parse:", str(pe))
    except Exception as e:
        print(s, "failed eval:", str(e), exprStack)