py: Add very simple but correct hashing for float and complex numbers.

dpgeorge · dpgeorge · commit 19f2e47d59b5 · 2017-04-04T11:57:21.000+10:00
Hashing of float and complex numbers that are exact (real) integers should
return the same integer hash value as hashing the corresponding integer
value.  Eg hash(1), hash(1.0) and hash(1+0j) should all be the same (this
is how Python is specified: if x==y then hash(x)==hash(y)).

This patch implements the simplest way of doing float/complex hashing by
just converting the value to int and returning that value.
diff --git a/py/obj.h b/py/obj.h
@@ -718,6 +718,7 @@ void mp_str_print_quoted(const mp_print_t *print, const byte *str_data, size_t s
 
 #if MICROPY_PY_BUILTINS_FLOAT
 // float
+static inline mp_int_t mp_float_hash(mp_float_t val) { return (mp_int_t)val; }
 mp_obj_t mp_obj_float_binary_op(mp_uint_t op, mp_float_t lhs_val, mp_obj_t rhs); // can return MP_OBJ_NULL if op not supported
 
 // complex
diff --git a/py/objcomplex.c b/py/objcomplex.c
@@ -117,6 +117,7 @@ STATIC mp_obj_t complex_unary_op(mp_uint_t op, mp_obj_t o_in) {
     mp_obj_complex_t *o = MP_OBJ_TO_PTR(o_in);
     switch (op) {
         case MP_UNARY_OP_BOOL: return mp_obj_new_bool(o->real != 0 || o->imag != 0);
+        case MP_UNARY_OP_HASH: return MP_OBJ_NEW_SMALL_INT(mp_float_hash(o->real) ^ mp_float_hash(o->imag));
         case MP_UNARY_OP_POSITIVE: return o_in;
         case MP_UNARY_OP_NEGATIVE: return mp_obj_new_complex(-o->real, -o->imag);
         default: return MP_OBJ_NULL; // op not supported
diff --git a/py/objfloat.c b/py/objfloat.c
@@ -106,6 +106,7 @@ STATIC mp_obj_t float_unary_op(mp_uint_t op, mp_obj_t o_in) {
     mp_float_t val = mp_obj_float_get(o_in);
     switch (op) {
         case MP_UNARY_OP_BOOL: return mp_obj_new_bool(val != 0);
+        case MP_UNARY_OP_HASH: return MP_OBJ_NEW_SMALL_INT(mp_float_hash(val));
         case MP_UNARY_OP_POSITIVE: return o_in;
         case MP_UNARY_OP_NEGATIVE: return mp_obj_new_float(-val);
         default: return MP_OBJ_NULL; // op not supported
