How Can I Evaluate Arithmetic Expressions from Strings in C Using ExprTk?

Evaluating Arithmetic Expressions from String in C

The task of evaluating simple arithmetic expressions from a string can be encountered in various programming contexts. While performing the evaluation, it's important to adhere to the mathematical order of operations, such as the precedence of multiplication over addition.

One widely recommended solution is to leverage the ExprTk library:

ExprTk Library

ExprTk is a lightweight C header-only library that simplifies the evaluation of mathematical expressions from strings. Here are its key benefits:

• Simplicity: It provides a straightforward interface with minimal dependencies.
• Functionality: It supports basic arithmetic operations ( , -, *, /) and parentheses.
• Control: Allows for dynamic modification of variable values within the expression.

Usage:

To utilize ExprTk, follow these steps:

1. Include "exprtk.hpp" in your source code.
2. Construct an ExprTk parser object.
3. Parse the expression string into the parser.
4. Evaluate the parsed expression to obtain the result.

Example:

#include <exprtk.hpp>
using namespace exprtk;

int main() {
  // Create a parser
  parser<double> parser;

  // Parse the expression string
  parser.compile("3*2+4*1+(4+9)*6");

  // Evaluate the expression
  double result = parser.value();

  // Output the result
  std::cout << result << std::endl;
}

This code will output the correct result: 87. ExprTk also allows for modifying variable values within the expression, providing flexibility and dynamic evaluation.

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