dc.rs

dc.rs (also dc-ock, for the Open Computing Kit) is a reverse Polish notation (postfix) calculator, roughly akin to the unix "dc" command, written in Rust. It lacks many of the more advanced features of dc, but still has core mathematical operations needed for most simple usage.

In addition to the command-line utility, dc.rs provides library components for other programs to use, including the RPN evaluator, the types and utility functions for said types.

Building dc.rs

...is a little bit awkward, but it's not too bad.

To build dc.rs, you'll need cargo.You can build the library with cargo build --lib, or you can build the executable with cargo build --features bbin --bin dc-cli.

It's a bit weird because there are binary-only dependencies, but rust doesn't support them yet, so we hack around it by using the --features flag. This stops massive downloads of the binary dependencies when you build the library.

Examples

Conversion from string to CalcType:

fn main() {
  let x: CalcType = str_to_calc_type("1").unwrap(); // returns Val(1.)
  let y: CalcType = str_to_calc_type("+").unwrap(); // returns Addition
  let z: CalcType = str_to_calc_type("*").unwrap(); // returns Multiplication
  // and so on.
}

Evaluating expressions safely:

fn main() {
    let expr = "1 2 +";
    match safe_eval(expr) {
        Ok(x) => println!("{:?}", x), // prints [3.0]
        Err(e) => println!("{}", e),  // prints an error message
    }
}  

Evaluating expressions with stack persistence:

fn main() {
    let mut stack: VecDeque<f64> = VecDeque::new();
    stack.push_back(2.);
    stack.push_back(7.5);
    stack.push_back(3.5);

    stack = safe_eval_with_stack("+ +", stack).unwrap();
    println!("{:?}", stack);
}