rust-expression 0.3.1

use rust_expression::{Area, Calculator, Graph, Value};

use linefeed::{Interface, ReadResult};

use std::io;
use std::sync::Arc;

fn draw(graph: &Graph) {
    const WIDTH: usize = 60;
    const HEIGHT: usize = 25;

    let area = Area::new(-100., -100., 100., 100.);
    let screen = Area::new(0., 0., WIDTH as f64, HEIGHT as f64);
    let plot = graph.plot(&area, &screen);

    match plot {
        Ok(plot) => {
            let mut chart = vec![vec![' '; WIDTH]; HEIGHT];

            for w in 0..WIDTH {
                let h = plot.points[w];
                if let Some(h) = h {
                    chart[HEIGHT - (h as usize)][w] = '*';
                }
            }

            for line in chart {
                let mut s = String::with_capacity(WIDTH as usize);
                for ch in line {
                    s.push(ch);
                }
                println!("{}", s);
            }
        }
        Err(err) => println!("{:?}", err),
    }
}

fn main() -> io::Result<()> {
    let interface = Arc::new(Interface::new("Calc")?);

    println!("This is the rust-expression repl program.");
    println!("Press Ctrl-D or \"quit\" to exit.");
    println!("");

    interface.set_prompt("% > ")?;

    let mut calc = Calculator::new();

    while let ReadResult::Input(line) = interface.read_line()? {
        if !line.trim().is_empty() {
            interface.add_history_unique(line.clone());
        }

        if "quit" == line {
            break;
        }

        match calc.execute(&line) {
            Ok(Value::Number(num)) => println!("{:}", num),
            Ok(Value::Void) => (),
            Ok(Value::Solved { variable, value }) => println!("{:} = {:}", variable, value),
            Ok(Value::Graph(graph)) => draw(&graph),
            Err(err) => println!("Error: {:}", err),
        }
    }

    println!("Goodbye.");

    Ok(())
}