From cde8631f15db9941986f8d04534e52462a76094b Mon Sep 17 00:00:00 2001
From: Rachel Dowdall <rjdowdall@gmail.com>
Date: Sat, 22 Mar 2014 17:29:27 +0000
Subject: [PATCH] Fixed modulo operator on ints and mp ints to agree with
 python. Added intdivmod.c and tests/basics/modulo.py.

---
 py/compile.c           |  4 +++-
 py/objint_mpz.c        |  5 ++++-
 py/py.mk               |  1 +
 py/runtime.c           |  9 ++++++---
 tests/basics/modulo.py | 23 +++++++++++++++++++++++
 5 files changed, 37 insertions(+), 5 deletions(-)
 create mode 100644 tests/basics/modulo.py

diff --git a/py/compile.c b/py/compile.c
index bb688d5d8..4eab09423 100644
--- a/py/compile.c
+++ b/py/compile.c
@@ -15,6 +15,7 @@
 #include "obj.h"
 #include "compile.h"
 #include "runtime.h"
+#include "intdivmod.h"
 
 // TODO need to mangle __attr names
 
@@ -141,7 +142,8 @@ mp_parse_node_t fold_constants(mp_parse_node_t pn) {
                         ; // pass
                     } else if (MP_PARSE_NODE_IS_TOKEN_KIND(pns->nodes[1], MP_TOKEN_OP_PERCENT)) {
                         // XXX implement this properly as Python's % operator acts differently to C's
-                        pn = mp_parse_node_new_leaf(MP_PARSE_NODE_SMALL_INT, arg0 % arg1);
+                        //pn = mp_parse_node_new_leaf(MP_PARSE_NODE_SMALL_INT, arg0 % arg1);
+                        pn = mp_parse_node_new_leaf(MP_PARSE_NODE_SMALL_INT, python_modulo(arg0, arg1));
                     } else if (MP_PARSE_NODE_IS_TOKEN_KIND(pns->nodes[1], MP_TOKEN_OP_DBL_SLASH)) {
                         // XXX implement this properly as Python's // operator acts differently to C's
                         pn = mp_parse_node_new_leaf(MP_PARSE_NODE_SMALL_INT, arg0 / arg1);
diff --git a/py/objint_mpz.c b/py/objint_mpz.c
index 21e3202a9..9c7727ba4 100644
--- a/py/objint_mpz.c
+++ b/py/objint_mpz.c
@@ -102,10 +102,13 @@ mp_obj_t int_binary_op(int op, mp_obj_t lhs_in, mp_obj_t rhs_in) {
             }
             case RT_BINARY_OP_MODULO:
             case RT_BINARY_OP_INPLACE_MODULO: {
-                // TODO check that this operation matches the CPython operation
                 mpz_t quo; mpz_init_zero(&quo);
                 mpz_divmod_inpl(&quo, &res->mpz, zlhs, zrhs);
                 mpz_deinit(&quo);
+		// Check signs and do Python style modulo
+		if (zlhs->neg != zrhs->neg) {
+                    mpz_add_inpl(&res->mpz, &res->mpz, zrhs);
+                }
                 break;
             }
 
diff --git a/py/py.mk b/py/py.mk
index 081417681..add871632 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -78,6 +78,7 @@ PY_O_BASENAME = \
 	vm.o \
 	showbc.o \
 	repl.o \
+	intdivmod.o \
 
 # prepend the build destination prefix to the py object files
 PY_O = $(addprefix $(PY_BUILD)/, $(PY_O_BASENAME))
diff --git a/py/runtime.c b/py/runtime.c
index 1cc1c2e6b..95c3a4415 100644
--- a/py/runtime.c
+++ b/py/runtime.c
@@ -18,6 +18,7 @@
 #include "builtin.h"
 #include "objarray.h"
 #include "bc.h"
+#include "intdivmod.h"
 
 #if 0 // print debugging info
 #define DEBUG_PRINT (1)
@@ -666,10 +667,12 @@ mp_obj_t rt_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
                 case RT_BINARY_OP_INPLACE_TRUE_DIVIDE: return mp_obj_new_float((mp_float_t)lhs_val / (mp_float_t)rhs_val);
                 #endif
 
-                // TODO implement modulo as specified by Python
                 case RT_BINARY_OP_MODULO:
-                case RT_BINARY_OP_INPLACE_MODULO: lhs_val %= rhs_val; break;
-
+                case RT_BINARY_OP_INPLACE_MODULO:
+                {
+                    lhs_val = python_modulo(lhs_val, rhs_val);
+                    break;
+                }
                 case RT_BINARY_OP_POWER:
                 case RT_BINARY_OP_INPLACE_POWER:
                     if (rhs_val < 0) {
diff --git a/tests/basics/modulo.py b/tests/basics/modulo.py
new file mode 100644
index 000000000..ce7ed2578
--- /dev/null
+++ b/tests/basics/modulo.py
@@ -0,0 +1,23 @@
+# check modulo matches python definition
+
+print(123 % 7)
+print(-123 % 7)
+print(123 % -7)
+print(-123 % -7)
+
+a = 321
+b = 19
+
+print(a % b)
+print(a % -b)
+print(-a % b)
+print(-a % -b)
+
+
+a = 987654321987987987987987987987
+b = 19
+
+print(a % b)
+print(a % -b)
+print(-a % b)
+print(-a % -b)