src/main/java/com/basistech/tclre/Compiler.java
private void optst(Subre t) {
        if (t == null) {
            return;
        }

    /* recurse through children */
        if (t.left != null) {
            optst(t.left);
        }
        if (t.right != null) {
            optst(t.right);
        }
    }
private void optst(Subre t) {
        if (t == null) {
            return;
        }

    /* recurse through children */
        if (t.left != null) {
            optst(t.left);
        }
        if (t.right != null) {
            optst(t.right);
        }
    }
optst - optimize a subRE subtree