Merge pull request #159 from chipaca/set_feats

Set features. As per #143.

py/map.c

@@ -132,28 +132,45 @@ void mp_set_init(mp_set_t *set, int n) {
     set->table = m_new0(mp_obj_t, set->alloc);
 }
 
-mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
-    int hash = mp_obj_hash(index);
-    assert(set->alloc); /* FIXME: if alloc is ever 0 when doing a lookup, this'll fail: */
-    int pos = hash % set->alloc;
+static void mp_set_rehash(mp_set_t *set) {
+    int old_alloc = set->alloc;
+    mp_obj_t *old_table = set->table;
+    set->alloc = get_doubling_prime_greater_or_equal_to(set->alloc + 1);
+    set->used = 0;
+    set->table = m_new0(mp_obj_t, set->alloc);
+    for (int i = 0; i < old_alloc; i++) {
+        if (old_table[i] != NULL) {
+            mp_set_lookup(set, old_table[i], true);
+        }
+    }
+    m_del(mp_obj_t, old_table, old_alloc);
+}
+
+mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, mp_map_lookup_kind_t lookup_kind) {
+    int hash;
+    int pos;
+    if (set->alloc == 0) {
+        if (lookup_kind & MP_MAP_LOOKUP_ADD_IF_NOT_FOUND) {
+            mp_set_rehash(set);
+        } else {
+            return NULL;
+        }
+    }
+    if (lookup_kind & MP_MAP_LOOKUP_FIRST) {
+        hash = 0;
+        pos = 0;
+    } else {
+        hash = mp_obj_hash(index);;
+        pos = hash % set->alloc;
+    }
     for (;;) {
         mp_obj_t elem = set->table[pos];
         if (elem == MP_OBJ_NULL) {
             // not in table
-            if (add_if_not_found) {
+            if (lookup_kind & MP_MAP_LOOKUP_ADD_IF_NOT_FOUND) {
                 if (set->used + 1 >= set->alloc) {
                     // not enough room in table, rehash it
-                    int old_alloc = set->alloc;
-                    mp_obj_t *old_table = set->table;
-                    set->alloc = get_doubling_prime_greater_or_equal_to(set->alloc + 1);
-                    set->used = 0;
-                    set->table = m_new(mp_obj_t, set->alloc);
-                    for (int i = 0; i < old_alloc; i++) {
-                        if (old_table[i] != NULL) {
-                            mp_set_lookup(set, old_table[i], true);
-                        }
-                    }
-                    m_del(mp_obj_t, old_table, old_alloc);
+                    mp_set_rehash(set);
                     // restart the search for the new element
                     pos = hash % set->alloc;
                 } else {
@@ -161,11 +178,17 @@ mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
                     set->table[pos] = index;
                     return index;
                 }
+            } else if (lookup_kind & MP_MAP_LOOKUP_FIRST) {
+                pos++;
             } else {
                 return MP_OBJ_NULL;
             }
-        } else if (mp_obj_equal(elem, index)) {
+        } else if (lookup_kind & MP_MAP_LOOKUP_FIRST || mp_obj_equal(elem, index)) {
             // found it
+            if (lookup_kind & MP_MAP_LOOKUP_REMOVE_IF_FOUND) {
+                set->used--;
+                set->table[pos] = NULL;
+            }
             return elem;
         } else {
             // not yet found, keep searching in this table
@@ -173,3 +196,13 @@ mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found) {
         }
     }
 }
+
+void mp_set_clear(mp_set_t *set) {
+    set->used = 0;
+    machine_uint_t a = set->alloc;
+    set->alloc = 0;
+    set->table = m_renew(mp_obj_t, set->table, a, set->alloc);
+    for (uint i=0; i<set->alloc; i++) {
+        set->table[i] = NULL;
+    }
+}

py/map.h

@@ -19,9 +19,10 @@ typedef struct _mp_set_t {
 } mp_set_t;
 
 typedef enum _mp_map_lookup_kind_t {
-    MP_MAP_LOOKUP,
-    MP_MAP_LOOKUP_ADD_IF_NOT_FOUND,
-    MP_MAP_LOOKUP_REMOVE_IF_FOUND,
+    MP_MAP_LOOKUP,                    // 0
+    MP_MAP_LOOKUP_ADD_IF_NOT_FOUND,   // 1
+    MP_MAP_LOOKUP_REMOVE_IF_FOUND,    // 2
+    MP_MAP_LOOKUP_FIRST = 4,
 } mp_map_lookup_kind_t;
 
 int get_doubling_prime_greater_or_equal_to(int x);
@@ -31,4 +32,5 @@ mp_map_elem_t* mp_map_lookup(mp_map_t *map, mp_obj_t index, mp_map_lookup_kind_t
 void mp_map_clear(mp_map_t *map);
 
 void mp_set_init(mp_set_t *set, int n);
-mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, bool add_if_not_found);
+mp_obj_t mp_set_lookup(mp_set_t *set, mp_obj_t index, mp_map_lookup_kind_t lookup_kind);
+void mp_set_clear(mp_set_t *set);

py/objset.c

 #include <stdlib.h>
 #include <stdint.h>
+#include <string.h>
 #include <assert.h>
 
 #include "nlr.h"
@@ -8,6 +9,7 @@
 #include "mpqstr.h"
 #include "obj.h"
 #include "runtime.h"
+#include "runtime0.h"
 #include "map.h"
 
 typedef struct _mp_obj_set_t {
@@ -15,8 +17,20 @@ typedef struct _mp_obj_set_t {
     mp_set_t set;
 } mp_obj_set_t;
 
+typedef struct _mp_obj_set_it_t {
+    mp_obj_base_t base;
+    mp_obj_set_t *set;
+    machine_uint_t cur;
+} mp_obj_set_it_t;
+
+static mp_obj_t set_it_iternext(mp_obj_t self_in);
+
 void set_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in) {
     mp_obj_set_t *self = self_in;
+    if (self->set.used == 0) {
+        print(env, "set()");
+        return;
+    }
     bool first = true;
     print(env, "{");
     for (int i = 0; i < self->set.alloc; i++) {
@@ -54,11 +68,382 @@ static mp_obj_t set_make_new(mp_obj_t type_in, int n_args, const mp_obj_t *args)
     }
 }
 
+const mp_obj_type_t set_it_type = {
+    { &mp_const_type },
+    "set_iterator",
+    .iternext = set_it_iternext,
+};
+
+static mp_obj_t set_it_iternext(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_it_type));
+    mp_obj_set_it_t *self = self_in;
+    machine_uint_t max = self->set->set.alloc;
+    mp_obj_t *table = self->set->set.table;
+
+    for (machine_uint_t i = self->cur; i < max; i++) {
+        if (table[i] != NULL) {
+            self->cur = i + 1;
+            return table[i];
+        }
+    }
+
+    return mp_const_stop_iteration;
+}
+
+static mp_obj_t set_getiter(mp_obj_t set_in) {
+    mp_obj_set_it_t *o = m_new_obj(mp_obj_set_it_t);
+    o->base.type = &set_it_type;
+    o->set = (mp_obj_set_t *)set_in;
+    o->cur = 0;
+    return o;
+}
+
+
+/******************************************************************************/
+/* set methods                                                                */
+
+static mp_obj_t set_add(mp_obj_t self_in, mp_obj_t item) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+    mp_set_lookup(&self->set, item, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_add_obj, set_add);
+
+static mp_obj_t set_clear(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+
+    mp_set_clear(&self->set);
+
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(set_clear_obj, set_clear);
+
+static mp_obj_t set_copy(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+
+    mp_obj_set_t *other = m_new_obj(mp_obj_set_t);
+    other->base.type = &set_type;
+    mp_set_init(&other->set, self->set.alloc - 1);
+    other->set.used = self->set.used;
+    memcpy(other->set.table, self->set.table, self->set.alloc * sizeof(mp_obj_t));
+
+    return other;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(set_copy_obj, set_copy);
+
+static mp_obj_t set_discard(mp_obj_t self_in, mp_obj_t item) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+    mp_set_lookup(&self->set, item, MP_MAP_LOOKUP_REMOVE_IF_FOUND);
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_discard_obj, set_discard);
+
+static mp_obj_t set_diff_int(int n_args, const mp_obj_t *args, bool update) {
+    assert(n_args > 0);
+    assert(MP_OBJ_IS_TYPE(args[0], &set_type));
+    mp_obj_set_t *self;
+    if (update) {
+        self = args[0];
+    } else {
+        self = set_copy(args[0]);
+    }
+
+
+    for (int i = 1; i < n_args; i++) {
+        mp_obj_t other = args[i];
+        if (self == other) {
+            set_clear(self);
+        } else {
+            mp_obj_t iter = rt_getiter(other);
+            mp_obj_t next;
+            while ((next = rt_iternext(iter)) != mp_const_stop_iteration) {
+                set_discard(self, next);
+            }
+        }
+    }
+
+    return self;
+}
+
+static mp_obj_t set_diff(int n_args, const mp_obj_t *args) {
+    return set_diff_int(n_args, args, false);
+}
+static MP_DEFINE_CONST_FUN_OBJ_VAR(set_diff_obj, 1, set_diff);
+
+static mp_obj_t set_diff_update(int n_args, const mp_obj_t *args) {
+    set_diff_int(n_args, args, true);
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_VAR(set_diff_update_obj, 1, set_diff_update);
+
+static mp_obj_t set_intersect_int(mp_obj_t self_in, mp_obj_t other, bool update) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    if (self_in == other) {
+        return update ? mp_const_none : set_copy(self_in);
+    }
+
+    mp_obj_set_t *self = self_in;
+    mp_obj_set_t *out = mp_obj_new_set(0, NULL);
+
+    mp_obj_t iter = rt_getiter(other);
+    mp_obj_t next;
+    while ((next = rt_iternext(iter)) != mp_const_stop_iteration) {
+        if (mp_set_lookup(&self->set, next, MP_MAP_LOOKUP)) {
+            set_add(out, next);
+        }
+    }
+
+    if (update) {
+        m_del(mp_obj_t, self->set.table, self->set.alloc);
+        self->set.alloc = out->set.alloc;
+        self->set.used = out->set.used;
+        self->set.table = out->set.table;
+    }
+
+    return update ? mp_const_none : out;
+}
+
+static mp_obj_t set_intersect(mp_obj_t self_in, mp_obj_t other) {
+    return set_intersect_int(self_in, other, false);
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_intersect_obj, set_intersect);
+
+static mp_obj_t set_intersect_update(mp_obj_t self_in, mp_obj_t other) {
+    return set_intersect_int(self_in, other, true);
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_intersect_update_obj, set_intersect_update);
+
+static mp_obj_t set_isdisjoint(mp_obj_t self_in, mp_obj_t other) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+
+    mp_obj_t iter = rt_getiter(other);
+    mp_obj_t next;
+    while ((next = rt_iternext(iter)) != mp_const_stop_iteration) {
+        if (mp_set_lookup(&self->set, next, MP_MAP_LOOKUP)) {
+            return mp_const_false;
+        }
+    }
+    return mp_const_true;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_isdisjoint_obj, set_isdisjoint);
+
+static mp_obj_t set_issubset_internal(mp_obj_t self_in, mp_obj_t other_in, bool proper) {
+    mp_obj_set_t *self;
+    bool cleanup_self = false;
+    if (MP_OBJ_IS_TYPE(self_in, &set_type)) {
+        self = self_in;
+    } else {
+        self = set_make_new(NULL, 1, &self_in);
+        cleanup_self = true;
+    }
+
+    mp_obj_set_t *other;
+    bool cleanup_other = false;
+    if (MP_OBJ_IS_TYPE(other_in, &set_type)) {
+        other = other_in;
+    } else {
+        other = set_make_new(NULL, 1, &other_in);
+        cleanup_other = true;
+    }
+    bool out = true;
+    if (proper && self->set.used == other->set.used) {
+        out = false;
+    } else {
+        mp_obj_t iter = set_getiter(self);
+        mp_obj_t next;
+        while ((next = set_it_iternext(iter)) != mp_const_stop_iteration) {
+            if (!mp_set_lookup(&other->set, next, MP_MAP_LOOKUP)) {
+                out = false;
+                break;
+            }
+        }
+    }
+    if (cleanup_self) {
+        set_clear(self);
+    }
+    if (cleanup_other) {
+        set_clear(other);
+    }
+    return MP_BOOL(out);
+}
+static mp_obj_t set_issubset(mp_obj_t self_in, mp_obj_t other_in) {
+    return set_issubset_internal(self_in, other_in, false);
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_issubset_obj, set_issubset);
+
+static mp_obj_t set_issubset_proper(mp_obj_t self_in, mp_obj_t other_in) {
+    return set_issubset_internal(self_in, other_in, true);
+}
+
+static mp_obj_t set_issuperset(mp_obj_t self_in, mp_obj_t other_in) {
+    return set_issubset_internal(other_in, self_in, false);
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_issuperset_obj, set_issuperset);
+
+static mp_obj_t set_issuperset_proper(mp_obj_t self_in, mp_obj_t other_in) {
+    return set_issubset_internal(other_in, self_in, true);
+}
+
+static mp_obj_t set_equal(mp_obj_t self_in, mp_obj_t other_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+    if (!MP_OBJ_IS_TYPE(other_in, &set_type)) {
+        return mp_const_false;
+    }
+    mp_obj_set_t *other = other_in;
+    if (self->set.used != other->set.used) {
+        return mp_const_false;
+    }
+    return set_issubset(self_in, other_in);
+}
+
+static mp_obj_t set_pop(mp_obj_t self_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+
+    if (self->set.used == 0) {
+        nlr_jump(mp_obj_new_exception_msg(MP_QSTR_KeyError, "pop from an empty set"));
+    }
+    mp_obj_t obj = mp_set_lookup(&self->set, NULL,
+                         MP_MAP_LOOKUP_REMOVE_IF_FOUND | MP_MAP_LOOKUP_FIRST);
+    return obj;
+}
+static MP_DEFINE_CONST_FUN_OBJ_1(set_pop_obj, set_pop);
+
+static mp_obj_t set_remove(mp_obj_t self_in, mp_obj_t item) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+    if (mp_set_lookup(&self->set, item, MP_MAP_LOOKUP_REMOVE_IF_FOUND) == MP_OBJ_NULL) {
+        nlr_jump(mp_obj_new_exception(MP_QSTR_KeyError));
+    }
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_remove_obj, set_remove);
+
+static mp_obj_t set_symmetric_difference_update(mp_obj_t self_in, mp_obj_t other_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = self_in;
+    mp_obj_t iter = rt_getiter(other_in);
+    mp_obj_t next;
+    while ((next = rt_iternext(iter)) != mp_const_stop_iteration) {
+        mp_set_lookup(&self->set, next, MP_MAP_LOOKUP_REMOVE_IF_FOUND | MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
+    }
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_symmetric_difference_update_obj, set_symmetric_difference_update);
+
+static mp_obj_t set_symmetric_difference(mp_obj_t self_in, mp_obj_t other_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    self_in = set_copy(self_in);
+    set_symmetric_difference_update(self_in, other_in);
+    return self_in;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_symmetric_difference_obj, set_symmetric_difference);
+
+static void set_update_int(mp_obj_set_t *self, mp_obj_t other_in) {
+    mp_obj_t iter = rt_getiter(other_in);
+    mp_obj_t next;
+    while ((next = rt_iternext(iter)) != mp_const_stop_iteration) {
+        mp_set_lookup(&self->set, next, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
+    }
+}
+
+static mp_obj_t set_update(int n_args, const mp_obj_t *args) {
+    assert(n_args > 0);
+    assert(MP_OBJ_IS_TYPE(args[0], &set_type));
+
+    for (int i = 1; i < n_args; i++) {
+        set_update_int(args[0], args[i]);
+    }
+
+    return mp_const_none;
+}
+static MP_DEFINE_CONST_FUN_OBJ_VAR(set_update_obj, 1, set_update);
+
+static mp_obj_t set_union(mp_obj_t self_in, mp_obj_t other_in) {
+    assert(MP_OBJ_IS_TYPE(self_in, &set_type));
+    mp_obj_set_t *self = set_copy(self_in);
+    set_update_int(self, other_in);
+    return self;
+}
+static MP_DEFINE_CONST_FUN_OBJ_2(set_union_obj, set_union);
+
+
+static mp_obj_t set_binary_op(int op, mp_obj_t lhs, mp_obj_t rhs) {
+    mp_obj_t args[] = {lhs, rhs};
+    switch (op) {
+    case RT_BINARY_OP_OR:
+        return set_union(lhs, rhs);
+    case RT_BINARY_OP_XOR:
+        return set_symmetric_difference(lhs, rhs);
+    case RT_BINARY_OP_AND:
+        return set_intersect(lhs, rhs);
+    case RT_BINARY_OP_SUBTRACT:
+        return set_diff(2, args);
+    case RT_BINARY_OP_INPLACE_OR:
+        return set_union(lhs, rhs);
+    case RT_BINARY_OP_INPLACE_XOR:
+        return set_symmetric_difference(lhs, rhs);
+    case RT_BINARY_OP_INPLACE_AND:
+        return set_intersect(lhs, rhs);
+    case RT_BINARY_OP_INPLACE_SUBTRACT:
+        return set_diff(2, args);
+    case RT_COMPARE_OP_LESS:
+        return set_issubset_proper(lhs, rhs);
+    case RT_COMPARE_OP_MORE:
+        return set_issuperset_proper(lhs, rhs);
+    case RT_COMPARE_OP_EQUAL:
+        return set_equal(lhs, rhs);
+    case RT_COMPARE_OP_LESS_EQUAL:
+        return set_issubset(lhs, rhs);
+    case RT_COMPARE_OP_MORE_EQUAL:
+        return set_issuperset(lhs, rhs);
+    case RT_COMPARE_OP_NOT_EQUAL:
+        return MP_BOOL(set_equal(lhs, rhs) == mp_const_false);
+    default:
+        // op not supported
+        return NULL;
+    }
+}
+
+/******************************************************************************/
+/* set constructors & public C API                                            */
+
+
+static const mp_method_t set_type_methods[] = {
+    { "add", &set_add_obj },
+    { "clear", &set_clear_obj },
+    { "copy", &set_copy_obj },
+    { "discard", &set_discard_obj },
+    { "difference", &set_diff_obj },
+    { "difference_update", &set_diff_update_obj },
+    { "intersection", &set_intersect_obj },
+    { "intersection_update", &set_intersect_update_obj },
+    { "isdisjoint", &set_isdisjoint_obj },
+    { "issubset", &set_issubset_obj },
+    { "issuperset", &set_issuperset_obj },
+    { "pop", &set_pop_obj },
+    { "remove", &set_remove_obj },
+    { "symmetric_difference", &set_symmetric_difference_obj },
+    { "symmetric_difference_update", &set_symmetric_difference_update_obj },
+    { "union", &set_union_obj },
+    { "update", &set_update_obj },
+    { NULL, NULL }, // end-of-list sentinel
+};
+
 const mp_obj_type_t set_type = {
     { &mp_const_type },
     "set",
     .print = set_print,
     .make_new = set_make_new,
+    .binary_op = set_binary_op,
+    .getiter = set_getiter,
+    .methods = set_type_methods,
 };
 
 mp_obj_t mp_obj_new_set(int n_args, mp_obj_t *items) {
@@ -66,7 +451,7 @@ mp_obj_t mp_obj_new_set(int n_args, mp_obj_t *items) {
     o->base.type = &set_type;
     mp_set_init(&o->set, n_args);
     for (int i = 0; i < n_args; i++) {
-        mp_set_lookup(&o->set, items[i], true);
+        mp_set_lookup(&o->set, items[i], MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
     }
     return o;
 }
@@ -74,5 +459,5 @@ mp_obj_t mp_obj_new_set(int n_args, mp_obj_t *items) {
 void mp_obj_set_store(mp_obj_t self_in, mp_obj_t item) {
     assert(MP_OBJ_IS_TYPE(self_in, &set_type));
     mp_obj_set_t *self = self_in;
-    mp_set_lookup(&self->set, item, true);
+    mp_set_lookup(&self->set, item, MP_MAP_LOOKUP_ADD_IF_NOT_FOUND);
 }

tests/basics/tests/set_add.py

+s = {1, 2, 3, 4}
+print(s.add(5))
+l = list(s)
+l.sort()
+print(l)

tests/basics/tests/set_binop.py

+def r(s):
+    l = list(s)
+    l.sort()
+    return l
+sets = [set(), {1}, {1, 2}, {1, 2, 3}, {2, 3}, {2, 3, 5}, {5}, {7}]
+for s in sets:
+    for t in sets:
+        print(s, '|', t, '=', r(s | t))
+        print(s, '^', t, '=', r(s ^ t))
+        print(s, '&', t, '=', r(s & t))
+        print(s, '-', t, '=', r(s - t))
+        u = s.copy()
+        u |= t
+        print(s, "|=", t, '-->', r(u))
+        u = s.copy()
+        u ^= t
+        print(s, "^=", t, '-->', r(u))
+        u = s.copy()
+        u &= t
+        print(s, "&=", t, "-->", r(u))
+        u = s.copy()
+        u -= t
+        print(s, "-=", t, "-->", r(u))
+
+        print(s, '==', t, '=', s == t)
+        print(s, '!=', t, '=', s != t)
+        print(s, '>', t, '=', s > t)
+        print(s, '>=', t, '=', s >= t)
+        print(s, '<', t, '=', s < t)
+        print(s, '<=', t, '=', s <= t)

tests/basics/tests/set_clear.py

+s = {1, 2, 3, 4}
+print(s.clear())
+print(list(s))

tests/basics/tests/set_copy.py

+s = {1, 2, 3, 4}
+t = s.copy()
+s.add(5)
+t.add(7)
+for i in s, t:
+    l = list(i)
+    l.sort()
+    print(l)

tests/basics/tests/set_difference.py

+def report(s):
+    l = list(s)
+    l.sort()
+    print(l)
+
+l = [1, 2, 3, 4]
+s = set(l)
+outs = [s.difference(),
+        s.difference({1}),
+        s.difference({1}, [1, 2]),
+        s.difference({1}, {1, 2}, {2, 3})]