@@ -0,0 +1,18 @@
+package ast
+
+func Find(node Node, fn func(node Node) bool) Node {
+v := &finder{fn: fn}
+Walk(&node, v)
+return v.node
+}
+
+type finder struct {
+node Node
+fn func(node Node) bool
+}
+
+func (f *finder) Visit(node *Node) {
+if f.fn(*node) {
+f.node = *node
+}
+}

@@ -0,0 +1,31 @@
+package ast_test
+
+import (
+"testing"
+
+".com/expr-lang/expr/internal/testify/require"
+
+".com/expr-lang/expr/ast"
+)
+
+func TestFind(t *testing.T) {
+left := &ast.IdentifierNode{
+Value: "a",
+}
+var root ast.Node = &ast.BinaryNode{
+Operator: "+",
+Left: left,
+Right: &ast.IdentifierNode{
+Value: "b",
+},
+}
+
+x := ast.Find(root, func(node ast.Node) bool {
+if n, ok := node.(*ast.IdentifierNode); ok {
+return n.Value == "a"
+}
+return false
+})
+
+require.Equal(t, left, x)
+}