67 lines
1.9 KiB
Rust
67 lines
1.9 KiB
Rust
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use egg::{RecExpr, Id};
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use crate::language::EquationLanguage;
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// there is already a Display implementation generated by define_langauge!
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// but we want an alternative string conversion
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pub fn print_term(expr: &RecExpr<EquationLanguage>) -> String {
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let root_id = Id::from(expr.as_ref().len()-1);
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print_term_inner(expr, root_id).0
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}
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// the second result is the precedence of the top level op: 1 = '+-', 2 = '*/', 3 = '^', 4 = primitive
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fn print_term_inner(expr: &RecExpr<EquationLanguage>, id: Id) -> (String, usize) {
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match &expr[id] {
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EquationLanguage::Num(c) => {
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(format!("{}", c), if c.denom == 1 { 4 } else { 2 })
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},
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EquationLanguage::Neg([a]) => {
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(print_unary(expr, *a, "-", 1), 1)
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},
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EquationLanguage::Add([a,b]) => {
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(print_binary(expr, *a, *b, "+", 1), 1)
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},
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EquationLanguage::Sub([a,b]) => {
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(print_binary(expr, *a, *b, "-", 1), 1)
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},
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EquationLanguage::Mul([a,b]) => {
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(print_binary(expr, *a, *b, "*", 2), 2)
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},
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EquationLanguage::Div([a,b]) => {
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(print_binary(expr, *a, *b, "/", 2), 2)
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},
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EquationLanguage::Power([a,b]) => {
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(print_binary(expr, *a, *b, "^", 3), 3)
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},
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_ => unimplemented!()
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}
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}
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fn print_unary(expr: &RecExpr<EquationLanguage>, a: Id, op: &str, precedence: usize) -> String {
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let (astr, aprec) = print_term_inner(expr, a);
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if aprec > precedence {
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format!("{}{}", op, astr)
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} else {
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format!("{}({})", op, astr)
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}
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}
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fn print_binary(expr: &RecExpr<EquationLanguage>, a: Id, b: Id, op: &str, precedence: usize) -> String {
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let (astr, aprec) = print_term_inner(expr, a);
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let (bstr, bprec) = print_term_inner(expr, b);
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if aprec > precedence {
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if bprec > precedence {
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format!("{} {} {}", astr, op, bstr)
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} else {
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format!("{} {} ({})", astr, op, bstr)
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}
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} else {
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if bprec > precedence {
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format!("({}) {} {}", astr, op, bstr)
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} else {
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format!("({}) {} ({})", astr, op, bstr)
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}
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}
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}
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