modbuiltins: Implement round() to precision.

1 files changed, 5 insertions, 4 deletions

diff --git a/py/modbuiltins.c b/py/modbuiltins.c
index 16b0e320c..d0c6130d5 100644
--- a/py/modbuiltins.c
+++ b/py/modbuiltins.c
@@ -431,7 +431,6 @@ STATIC mp_obj_t mp_builtin_repr(mp_obj_t o_in) {
 MP_DEFINE_CONST_FUN_OBJ_1(mp_builtin_repr_obj, mp_builtin_repr);
 
 STATIC mp_obj_t mp_builtin_round(mp_uint_t n_args, const mp_obj_t *args) {
-    // TODO really support second arg
     mp_obj_t o_in = args[0];
     if (MP_OBJ_IS_INT(o_in)) {
         return o_in;
@@ -440,9 +439,11 @@ STATIC mp_obj_t mp_builtin_round(mp_uint_t n_args, const mp_obj_t *args) {
     mp_int_t num_dig = 0;
     if (n_args > 1) {
         num_dig = mp_obj_get_int(args[1]);
-        if (num_dig > 0) {
-            mp_not_implemented("round(..., N>0)");
-        }
+        mp_float_t val = mp_obj_get_float(o_in);
+        mp_float_t mult = MICROPY_FLOAT_C_FUN(pow)(10, num_dig);
+        // TODO may lead to overflow
+        mp_float_t rounded = MICROPY_FLOAT_C_FUN(round)(val * mult) / mult;
+        return mp_obj_new_float(rounded);
     }
     mp_float_t val = mp_obj_get_float(o_in);
     mp_float_t rounded = MICROPY_FLOAT_C_FUN(round)(val);