wow it works

src/ast.rs

@@ -0,0 +1,28 @@
+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()
+}