Struct rust_expression::Calculator

pub struct Calculator { /* fields omitted */ }

Calculator

See it in action on https://msuesskraut.github.io/calc/index.html. Further examples are in Calculator::execute.

Implementations

impl Calculator

pub fn new() -> Self

constructs an calculator without any known variables

pub fn execute(&mut self, line: &str) -> Result<Option<f64>, Error>

Executes a command line. 3 kinds of statements are supported:

• Expression:

  use rust_expression::Calculator;
  let mut c = Calculator::new();
  assert_eq!(Ok(Some(3.0)), c.execute("1 + 2"));

• Variable assignments:

  assert_eq!(Ok(None), c.execute("a := 6"));
  assert_eq!(Ok(Some(36.0)), c.execute("a ^ 2"));

• Solving linear expressions:

  assert_eq!(Ok(Some(4.0)), c.execute("solve 3 * x - 2 = x + a for x"));

• Function definition:

  assert_eq!(Ok(None), c.execute("fun(x, y) := y - x"));
  assert_eq!(Ok(Some(20.0)), c.execute("fun(1 + 2, 3 * 9) - 4"));

Trait Implementations

impl Debug for Calculator

pub fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Calculator

pub fn default() -> Calculator

Returns the "default value" for a type.