calculator.rs

use gui::{
    widget::{Toggle, Button, Label, List},
    layout::Direction,
    event::Click,
    Window, Widget,
};

fn main() {
    enum Op {
        Add,
        Sub,
        Mul,
        Div,
    }

    struct Data {
        screen: String,
        second: f64,
        op: Option<Op>,
    }

    impl Data {
        fn start_op(&mut self, op: Op) {
            self.second = std::mem::take(&mut self.screen).parse().unwrap();
            self.op = Some(op);
        }

        fn calc(&mut self) {
            let screen = self.screen.parse().unwrap_or(0.0);
            self.screen = match self.op.take() {
                Some(Op::Add) => self.second + screen,
                Some(Op::Sub) => self.second - screen,
                Some(Op::Mul) => self.second * screen,
                Some(Op::Div) => self.second / screen,
                None => return,
            }.to_string();
        }
    }

    let num_button = |n: &'static str| Button::<Data>::default_state()
        .containing(Label::<Data>::with_state(n).padded(16.0))
        .on(Click, move |ctx| ctx.data.screen.push_str(&n))
        .padded(8.0);

    let ui = List::<Data>::vertical()
        .push(Button::<Data>::default_state()
            .containing(Label::<Data>::bind_state(|d| &mut d.screen).padded(16.0))
            .padded(8.0))
        .push(List::<Data>::horizontal()
            .push(num_button("1"))
            .push(num_button("2"))
            .push(num_button("3"))
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("+").padded(16.0))
                .on(Click, |ctx| ctx.data.start_op(Op::Add))
                .padded(8.0)))
        .push(List::<Data>::horizontal()
            .push(num_button("4"))
            .push(num_button("5"))
            .push(num_button("6"))
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("-").padded(16.0))
                .on(Click, |ctx| ctx.data.start_op(Op::Sub))
                .padded(8.0)))
        .push(List::<Data>::horizontal()
            .push(num_button("7"))
            .push(num_button("8"))
            .push(num_button("9"))
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("*").padded(16.0))
                .on(Click, |ctx| ctx.data.start_op(Op::Mul))
                .padded(8.0)))
        .push(List::<Data>::horizontal()
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("C").padded(16.0))
                .on(Click, |ctx| ctx.data.screen.clear())
                .padded(8.0))
            .push(num_button("0"))
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("=").padded(16.0))
                .on(Click, |ctx| ctx.data.calc())
                .padded(8.0))
            .push(Button::<Data>::default_state()
                .containing(Label::<Data>::with_state("/").padded(16.0))
                .on(Click, |ctx| ctx.data.start_op(Op::Div))
                .padded(8.0)))
        .padded(8.0);

    Window::new(ui)
        .run(Data {
            screen: String::new(),
            second: 0.0,
            op: None,
        })
}