dayan 0.0.1

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Documentation 
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use super::*;

impl Display for ExpressionTree {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            ExpressionTree::Number(v) => f.write_fmt(format_args!("{}", v))?,
            ExpressionTree::Letter(v) => f.write_fmt(format_args!("{}", v))?,
            ExpressionTree::Sum { add } => {
                for (i, term) in add.iter().enumerate() {
                    if i != 0 {
                        f.write_str(" + ")?;
                    }
                    Display::fmt(term, f)?;
                }
            }
            ExpressionTree::Product { mul } => {
                for (i, term) in mul.iter().enumerate() {
                    if i != 0 {
                        f.write_str(" × ")?;
                    }
                    Display::fmt(term, f)?;
                }
            }
            ExpressionTree::Sup { base: head, rest } => {
                Display::fmt(head, f)?;
                f.write_char('^')?;
                write_bracketed(f, rest)?
            }
            // a_{b_c}
            ExpressionTree::Subscript { base, rest } => {
                Display::fmt(base, f)?;
                f.write_char('_')?;
                write_bracketed(f, rest)?
            }
            ExpressionTree::Function { body } => {

                Display::fmt(body, f)?;

            }
        }
        Ok(())
    }
}

impl Display for FunctionExpression {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        f.write_char(self.name)?;
        for term in &self.sup {
            f.write_char('^')?;
            write_bracketed(f, term)?
        }
        for term in &self.sub {
            f.write_char('_')?;
            write_bracketed(f, term)?
        }
        f.write_char('(')?;
        for (i, term) in self.args.iter().enumerate() {
            if i != 0 {
                f.write_str(", ")?;
            }
            Display::fmt(term, f)?;
        }
        f.write_char(')')
    }
}

fn write_bracketed(f: &mut Formatter<'_>, rest: &ExpressionTree) -> std::fmt::Result {
    if rest.is_digit() {
        Display::fmt(rest, f)
    }
    else {
        f.write_str("{")?;
        Display::fmt(rest, f)?;
        f.write_char('}')
    }
}