eval

Arithmetic expression evalutaion in C/C++.

Usage

double eval(const char *expr);

Returns the result of expr.

double eval_v(const char *expr, const EvalValues *values);

Returns the result of expr, with constants/variables from values.

int eval_assign(const char *expression, const EvalValue *values);

Performs assignment to a variable from values.

Format of expression: val = expr (whitespace does not matter), where val recieves the result of evaluating expr.

The values array

Example:

const EvalValue values[] = {
  EvalConst("pi", 3.14159),
  EvalConst("e", 2.71828),
  EvalVar("argc", &argc),
  EvalEnd
};

• EvalConst Creates a constant value
• EvalVar Uses the value of the pointed to variable
• EvalEnd Terminates the array

Features

• Operators: +, -, * and /
• Operator precedences
• Parentheses
• Variables and constants
• Assignment expressions
• Implicit multiplication with parentheses

Operator precedence disambiguation

By default an expression like 48 / 2(9 + 3) is interpreted as 48 / (2 * (9 + 3)). When compiling with -DEVAL_DISAMBIG_ALT, it gets changed to (48 / 2) * (9 + 3).