local env = environment() local group = Const("group") local carrier = Const("carrier") local real = Const("real") local nat = Const("nat") env = add_decl(env, mk_var_decl("group", mk_sort(2))) env = add_decl(env, mk_var_decl("carrier", mk_arrow(group, Type))) env = add_decl(env, mk_var_decl("real", Type)) env = add_decl(env, mk_var_decl("nat", Type)) env = add_decl(env, mk_var_decl("real_group", group)) env = add_decl(env, mk_var_decl("nat_group", group)) local real_group = Const("real_group") local nat_group = Const("nat_group") local m = mk_metavar("m", mk_metavar("m_ty", mk_sort(mk_meta_univ("u")))) local cs = { mk_eq_cnstr(carrier(m), real) } local o = options({"unifier", "use_exceptions"}, false) print(o) assert(not unify(env, cs, o)()) function hint(c, ngen) local lhs = c:lhs() local rhs = c:rhs() local j = c:justification() if lhs:is_app() and lhs:fn() == carrier and lhs:arg():is_meta() then return {{ mk_eq_cnstr(lhs:arg(), nat_group, j) }, -- first possible solution { mk_eq_cnstr(lhs:arg(), real_group, j) }} else return nil end end function display_solutions(ss) local n = 0 for s in ss do print("solution: ") s:for_each_expr(function(n, v, j) print(" " .. tostring(n) .. " := " .. tostring(v)) end) s:for_each_level(function(n, v, j) print(" " .. tostring(n) .. " := " .. tostring(v)) end) n = n + 1 end end display_solutions(unify(env, cs, hint, o))