diff --git a/notebook/scratch.ipynb b/notebook/scratch.ipynb
index 10006e2..02ebec2 100644
--- a/notebook/scratch.ipynb
+++ b/notebook/scratch.ipynb
@@ -626,6 +626,34 @@
     " output [balanced RANK from 5d[highest 3 of 4d6]]\n",
     "}"
    ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 5,
+   "metadata": {},
+   "outputs": [
+    {
+     "data": {
+      "text/plain": [
+       "True"
+      ]
+     },
+     "execution_count": 5,
+     "metadata": {},
+     "output_type": "execute_result"
+    }
+   ],
+   "source": [
+    "class rand:\n",
+    "  pass\n",
+    "class Var:\n",
+    "  mytype = object()\n",
+    "  def __init__(self, value):\n",
+    "    self.value = value\n",
+    "  def __eq__(self, other):\n",
+    "    return self.value == other.value\n",
+    "Var(Var.mytype) == Var(Var.mytype)"
+   ]
   }
  ],
  "metadata": {
diff --git a/src/__init__.py b/src/__init__.py
index e66ccfe..81fc17f 100644
--- a/src/__init__.py
+++ b/src/__init__.py
@@ -1,8 +1,9 @@
-__version__ = '0.3.2'
+__version__ = '0.3.2.dev0'
 
 # core classes
 from .randvar import RV
 from .seq import Seq
+from .factory import get_seq
 
 # core functions
 from .roller import myrange
@@ -29,7 +30,7 @@
 
 __all__ = [
   'RV', 'Seq', 'anydice_casting', 'BlankRV', 'max_func_depth', 'output', 'roll', 'settings_set', 'myrange',
-  'roller', 'settings_reset', 'StringSeq',
+  'roller', 'settings_reset', 'StringSeq', 'get_seq',
   'absolute_X', 'X_contains_X', 'count_X_in_X', 'explode_X', 'highest_X_of_X', 'lowest_X_of_X', 'middle_X_of_X', 'highest_of_X_and_X', 'lowest_of_X_and_X', 'maximum_of_X', 'reverse_X', 'sort_X',
   'myMatmul', 'myLen', 'myInvert', 'myAnd', 'myOr'
 ]
diff --git a/src/blackrv.py b/src/blackrv.py
index 44f71eb..0736538 100644
--- a/src/blackrv.py
+++ b/src/blackrv.py
@@ -1,3 +1,4 @@
+# TODO rename file to blankrv.py
 from typing import Iterable
 
 from . import randvar as rv
diff --git a/src/factory.py b/src/factory.py
new file mode 100644
index 0000000..3806ec6
--- /dev/null
+++ b/src/factory.py
@@ -0,0 +1,24 @@
+from typing import Union
+
+from .typings import T_if, T_ifsr
+from . import randvar
+from . import seq
+from . import utils
+from . import blackrv
+from . import string_rvs
+
+
+T_ifsrt = Union[T_ifsr, str]
+
+
+def get_seq(*source: T_ifsrt) -> 'seq.Seq':
+  # check if string in values, if so, return StringSeq
+  flat = tuple(utils.flatten(source))
+  flat_rvs = [x for x in flat if isinstance(x, randvar.RV) and not isinstance(x, blackrv.BlankRV)]  # expand RVs
+  flat_rv_vals = [v for rv in flat_rvs for v in rv.vals]
+  flat_else: list[T_if] = [x for x in flat if not isinstance(x, (randvar.RV, blackrv.BlankRV))]
+  res = tuple(flat_else + flat_rv_vals)
+  if any(isinstance(x, (str, string_rvs.StringVal)) for x in res):
+    return string_rvs.StringSeq(res)
+  assert all(isinstance(x, (int, float)) for x in res), 'Seq must be made of numbers and RVs. Seq:' + str(res)
+  return seq.Seq(_INTERNAL_SEQ_VALUE=res)
diff --git a/src/parser/parse_and_exec.py b/src/parser/parse_and_exec.py
index 1c0601e..045f13a 100644
--- a/src/parser/parse_and_exec.py
+++ b/src/parser/parse_and_exec.py
@@ -46,7 +46,8 @@ def _get_lib():
   import random
   import functools
   from ..randvar import RV
-  from ..seq import Seq, get_seq
+  from ..seq import Seq
+  from ..factory import get_seq
   from ..settings import settings_set
   from ..decorators import anydice_casting, max_func_depth
   from ..output import output
diff --git a/src/seq.py b/src/seq.py
index 6b8f7c8..a463416 100644
--- a/src/seq.py
+++ b/src/seq.py
@@ -7,21 +7,8 @@
 from . import utils
 from . import blackrv
 
-T_ift = Union[T_if, str]
-
 
-def get_seq(*source: T_ifsr) -> 'Seq':
-  # check if string in values, if so, return StringSeq
-  flat = tuple(utils.flatten(source))
-  flat_rvs = [x for x in flat if isinstance(x, randvar.RV) and not isinstance(x, blackrv.BlankRV)]  # expand RVs
-  flat_rv_vals = [v for rv in flat_rvs for v in rv.vals]
-  flat_else: list[T_if] = [x for x in flat if not isinstance(x, (randvar.RV, blackrv.BlankRV))]
-  res = tuple(flat_else + flat_rv_vals)
-  if any(isinstance(x, str) for x in res):
-    from .string_rvs import StringSeq
-    return StringSeq(res)
-  assert all(isinstance(x, (int, float)) for x in flat_else), 'Seq must be made of numbers and RVs. Seq:' + str(flat_else)
-  return Seq(_INTERNAL_SEQ_VALUE=res)
+T_ift = Union[T_if, str]
 
 
 class Seq(Iterable):
diff --git a/src/string_rvs.py b/src/string_rvs.py
index 444f985..48097b1 100644
--- a/src/string_rvs.py
+++ b/src/string_rvs.py
@@ -1,26 +1,40 @@
 
-from typing import Union
+from typing import Union, Literal
 import operator as op
 
 from .typings import T_if
-from .seq import Seq
+from . import seq
 
 T_ift = Union[T_if, str, 'StringVal']
 
 
+_CONST_COEF = '_UNIQUE_STRING'
+
+
 class StringVal:
-  def __init__(self, keys: tuple[str, ...], pairs: dict[str, int]):
-    self.keys = keys
+  def __init__(self, keys: tuple[str, ...], pairs: dict[str, T_if]):
+    self.keys = tuple(sorted(keys))
     self.data = pairs
 
+  @staticmethod
+  def from_const(const: T_if):
+    return StringVal((_CONST_COEF, ), {_CONST_COEF: const})
+
+  @staticmethod
+  def from_str(s: str):
+    return StringVal((s, ), {s: 1})
+
+  @staticmethod
+  def from_paris(pairs: dict[str, T_if]):  # TODO rename to from_pairs
+    return StringVal(tuple(pairs.keys()), pairs)
+
   def __add__(self, other):
     if not isinstance(other, StringVal):
-      other = StringVal(('', ), {'': other})
+      other = StringVal.from_const(other)
     newdict = self.data.copy()
     for key, val in other.data.items():
       newdict[key] = newdict.get(key, 0) + val
-    keys = tuple(sorted(newdict.keys()))
-    return StringVal(keys, newdict)
+    return StringVal.from_paris(newdict)
 
   def __radd__(self, other):
     return self.__add__(other)
@@ -29,15 +43,15 @@ def __repr__(self):
     r = []
     last_coeff = ''
     for key in self.keys:
-      if key == '':  # empty string represents a number
-        last_coeff = '+' + str(self.data[key])
+      if key == _CONST_COEF:  # empty string represents a number
+        last_coeff = ' + ' + str(self.data[key])
         continue
       elif self.data[key] == 1:  # coefficient 1 is not shown
         n = key
       else:
         n = f'{self.data[key]}*{key}'
       r.append(n)
-    return '+'.join(r) + last_coeff
+    return ' + '.join(r) + last_coeff
 
   def __format__(self, format_spec):
     return f'{repr(self):{format_spec}}'
@@ -84,11 +98,14 @@ def __hash__(self):
     return hash((self.keys, tuple(self.data)))
 
 
-class StringSeq(Seq):
+class StringSeq(seq.Seq):
   def __init__(self, source: tuple[T_ift, ...]):
     # do not call super().__init__ here
     source_lst: list[T_ift] = list(source)
     for i, x in enumerate(source_lst):
       if isinstance(x, str):
-        source_lst[i] = StringVal((x, ), {x: 1})
+        source_lst[i] = StringVal.from_str(x)
     self._seq: tuple[T_ift, ...] = tuple(source_lst)
+
+  def __iter__(self):
+    return iter(self._seq)
diff --git a/test/stringvar_test.py b/test/stringvar_test.py
new file mode 100644
index 0000000..b7e824c
--- /dev/null
+++ b/test/stringvar_test.py
@@ -0,0 +1,94 @@
+from typing import Iterable
+import pytest
+
+from dice_calc import settings_reset, get_seq, roll, RV
+from dice_calc.string_rvs import StringVal
+
+
+@pytest.fixture(autouse=True)
+def settings_reset_fixture():
+  settings_reset()
+
+
+def test_init():
+  a = StringVal(('a', 'b'), {'a': 1, 'b': 2})
+  b = StringVal(('a', 'b'), {'a': 1, 'b': 2})
+  c = StringVal(('b', 'a'), {'b': 2, 'a': 1})
+  d = StringVal(('a', 'b', 'c'), {'a': 1, 'b': 2, 'c': 3})
+  assert a == b
+  assert a == c
+  assert b == c
+  assert a != d
+  assert b != d
+  assert c != d
+
+
+def test_format():
+  a = StringVal(('a', 'b'), {'a': 1, 'b': 2})
+  assert f'{a}' == 'a + 2*b'
+
+
+def test_compare():
+  a = StringVal(('a', 'b'), {'a': 1, 'b': 2})
+  b = StringVal(('b', 'a'), {'b': 2, 'a': 1})
+  c = StringVal(('b', 'a'), {'b': 1, 'a': 1})
+  assert a == b
+  assert a <= b
+  assert a >= b
+  assert not (a < b)
+  assert not (a > b)
+  assert not (a != b)
+
+  assert a > c
+  assert a >= c
+  assert not (a < c)
+  assert not (a <= c)
+  assert not (a == c)
+  assert a != c
+
+
+def test_hash():
+  a = StringVal(('a', 'b'), {'a': 1, 'b': 2})
+  c = StringVal(('b', 'a'), {'b': 1, 'a': 1})
+  d = StringVal(('a', 'b', 'c'), {'a': 1, 'b': 2, 'c': 3})
+  assert hash(a) != hash(c)
+  assert hash(a) != hash(d)
+  assert hash(c) != hash(d)
+  assert hash(a) == hash(a)
+  assert hash(c) == hash(c)
+  assert hash(d) == hash(d)
+
+
+def test_get_seq():
+  a = get_seq('a', 'b')
+  b = get_seq('a', 'b')
+  c = get_seq(1, 2)
+  d = get_seq(1, 2)
+  e = get_seq(1, 2, 'a', 'b')
+  assert a == b
+  assert c == d
+  assert a != c
+  assert a != e
+  assert c != e
+  assert isinstance(a, Iterable), 'get_seq must return an iterable'
+  assert a == get_seq(a)
+  assert e == get_seq(e)
+
+
+def test_roll():
+  a = get_seq(roll(1, 2), 'fire', 'water')  # {1d2, "water", "fire"}
+  b = roll(2, a)  # 2dA
+  vp = [
+    (2, 1),
+    (3, 2),
+    (4, 1),
+    ((StringVal.from_str('fire') + StringVal.from_const(1)), 2),
+    ((StringVal.from_str('fire') + StringVal.from_const(2)), 2),
+    ((StringVal.from_str('water') + StringVal.from_const(1)), 2),
+    ((StringVal.from_str('water') + StringVal.from_const(2)), 2),
+    ((StringVal.from_str('fire') + StringVal.from_str('water')), 2),
+    ((StringVal.from_str('water') + StringVal.from_str('water')), 1),
+    ((StringVal.from_str('fire') + StringVal.from_str('fire')), 1),
+  ]
+  # assert not sum(b.probs)
+  assert RV.dices_are_equal(b, RV(vals=[x[0] for x in vp], probs=[x[1] for x in vp]))