use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum Prim {
    Sin,
    Cos,
    Triple,  // 3 * x
    AddPair, // (a,b) -> a + b
    Input,   // переменная x
}

#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub enum ExprAst {
    Atom(Prim),
    Composition(Box<ExprAst>, Box<ExprAst>), // g ∘ f
    Junction(Box<ExprAst>, Box<ExprAst>),    // (f, g)
}

pub fn ast_input() -> ExprAst {
    ExprAst::Atom(Prim::Input)
}

pub fn hash_ast(e: &ExprAst) -> u64 {
    let mut h = DefaultHasher::new();
    e.hash(&mut h);
    h.finish()
}