egraphs-good · saulshanabrook · Aug 10, 2023 · Aug 10, 2023 · Aug 10, 2023
diff --git a/docs/changelog.md b/docs/changelog.md
@@ -21,6 +21,7 @@ _This project uses semantic versioning. Before 1.0.0, this means that every brea
   - Upgraded `egg-smol` dependency ([changes](https://github.com/saulshanabrook/egg-smol/compare/353c4387640019bd2066991ee0488dc6d5c54168...2ac80cb1162c61baef295d8e6d00351bfe84883f))
 
 - Add support for functions which mutates their args, like `__setitem__` [#35](https://github.com/metadsl/egglog-python/pull/35)
+- Makes conversions transitive [#38](https://github.com/metadsl/egglog-python/pull/38)
 
 ## 0.5.1 (2023-07-18)
 

diff --git a/docs/reference/egglog-translation.md b/docs/reference/egglog-translation.md
@@ -255,6 +255,8 @@ Math(2) + 30 + "x"
 Math(2) + Math(i64(30)) + Math.var(String("x"))
 ```
 
+Regstering a conversion from A to B will also register all transitively reachable conversions from A to B.
+
 ### Declarations
 
 In egglog, the `(declare ...)` command is syntactic sugar for a nullary function. In Python, these can be declare either as class variables or with the toplevel `egraph.constant` function:

diff --git a/docs/tutorials/array-api.ipynb b/docs/tutorials/array-api.ipynb
diff --git a/python/egglog/exp/array_api.py b/python/egglog/exp/array_api.py
@@ -1,5 +1,3 @@
-# mypy: disable-error-code=empty-body
-
 from __future__ import annotations
 
 import itertools
@@ -13,6 +11,9 @@
 # Pretend that exprs are numbers b/c scikit learn does isinstance checks
 from egglog.runtime import RuntimeExpr
 
+# mypy: disable-error-code=empty-body
+
+
 numbers.Integral.register(RuntimeExpr)
 
 egraph = EGraph()
@@ -111,7 +112,6 @@ def isdtype(dtype: DType, kind: IsDtypeKind) -> Bool:
     ...
 
 
-converter(np.dtype, IsDtypeKind, lambda x: IsDtypeKind.dtype(convert(x, DType)))
 converter(DType, IsDtypeKind, lambda x: IsDtypeKind.dtype(x))
 converter(str, IsDtypeKind, lambda x: IsDtypeKind.string(x))
 converter(
@@ -286,23 +286,108 @@ def _tuple_int(ti: TupleInt, ti2: TupleInt, i: Int, i2: Int, k: i64):
     ]
 
 
-# HANDLED_FUNCTIONS = {}
+@egraph.class_
+class OptionalInt(Expr):
+    none: ClassVar[OptionalInt]
+
+    @classmethod
+    def some(cls, value: Int) -> OptionalInt:
+        ...
+
+
+converter(type(None), OptionalInt, lambda x: OptionalInt.none)
+converter(Int, OptionalInt, OptionalInt.some)
 
 
 @egraph.class_
-class IndexKey(Expr):
+class Slice(Expr):
+    def __init__(self, start: OptionalInt, stop: OptionalInt, step: OptionalInt) -> None:
+        ...
+
+
+converter(
+    slice,
+    Slice,
+    lambda x: Slice(convert(x.start, OptionalInt), convert(x.stop, OptionalInt), convert(x.step, OptionalInt)),
+)
+
+
+@egraph.class_
+class MultiAxisIndexKeyItem(Expr):
+    ELLIPSIS: ClassVar[MultiAxisIndexKeyItem]
+    NONE: ClassVar[MultiAxisIndexKeyItem]
+
     @classmethod
-    def tuple_int(cls, ti: TupleInt) -> IndexKey:
+    def int(cls, i: Int) -> MultiAxisIndexKeyItem:
         ...
 
+    @classmethod
+    def slice(cls, slice: Slice) -> MultiAxisIndexKeyItem:
+        ...
+
+
+converter(type(...), MultiAxisIndexKeyItem, lambda x: MultiAxisIndexKeyItem.ELLIPSIS)
+converter(type(None), MultiAxisIndexKeyItem, lambda x: MultiAxisIndexKeyItem.NONE)
+converter(Int, MultiAxisIndexKeyItem, MultiAxisIndexKeyItem.int)
+converter(Slice, MultiAxisIndexKeyItem, MultiAxisIndexKeyItem.slice)
+
+
+@egraph.class_
+class MultiAxisIndexKey(Expr):
+    def __init__(self, item: MultiAxisIndexKeyItem) -> None:
+        ...
+
+    EMPTY: ClassVar[MultiAxisIndexKey]
+
+    def __add__(self, other: MultiAxisIndexKey) -> MultiAxisIndexKey:
+        ...
+
+
+converter(
+    tuple,
+    MultiAxisIndexKey,
+    lambda x: MultiAxisIndexKey(convert(x[0], MultiAxisIndexKeyItem)) + convert(x[1:], MultiAxisIndexKey)
+    if x
+    else MultiAxisIndexKey.EMPTY,
+)
+
+
+@egraph.class_
+class IndexKey(Expr):
+    """
+    A key for indexing into an array
+
+    https://data-apis.org/array-api/2022.12/API_specification/indexing.html
+
+    It is equivalent to the following type signature:
+
+    Union[int, slice, ellipsis, Tuple[Union[int, slice, ellipsis, None], ...], array]
+    """
+
+    ELLIPSIS: ClassVar[IndexKey]
+
     @classmethod
     def int(cls, i: Int) -> IndexKey:
         ...
 
+    @classmethod
+    def slice(cls, slice: Slice) -> IndexKey:
+        ...
+
+    # Disabled until we support late binding
+    # @classmethod
+    # def boolean_array(cls, b: NDArray) -> IndexKey:
+    #     ...
+
+    @classmethod
+    def multi_axis(cls, key: MultiAxisIndexKey) -> IndexKey:
+        ...
+
 
-converter(tuple, IndexKey, lambda x: IndexKey.tuple_int(convert(x, TupleInt)))
-converter(int, IndexKey, lambda x: IndexKey.int(Int(x)))
-converter(Int, IndexKey, lambda x: IndexKey.int(x))
+converter(type(...), IndexKey, lambda x: IndexKey.ELLIPSIS)
+converter(Int, IndexKey, IndexKey.int)
+converter(Slice, IndexKey, IndexKey.slice)
+converter(MultiAxisIndexKey, IndexKey, IndexKey.multi_axis)
 
 
 @egraph.class_
@@ -400,8 +485,8 @@ def ndarray_index(x: NDArray) -> IndexKey:
 converter(NDArray, IndexKey, ndarray_index)
 
 
-converter(float, NDArray, lambda x: NDArray.scalar_float(Float(x)))
-converter(int, NDArray, lambda x: NDArray.scalar_int(Int(x)))
+converter(Float, NDArray, NDArray.scalar_float)
+converter(Int, NDArray, NDArray.scalar_int)
 
 
 @egraph.register
@@ -478,7 +563,6 @@ def some(cls, value: Bool) -> OptionalBool:
 
 converter(type(None), OptionalBool, lambda x: OptionalBool.none)
 converter(Bool, OptionalBool, lambda x: OptionalBool.some(x))
-converter(bool, OptionalBool, lambda x: OptionalBool.some(convert(x, Bool)))
 
 
 @egraph.class_
@@ -518,6 +602,7 @@ def some(cls, value: TupleInt) -> OptionalTupleInt:
 
 converter(type(None), OptionalTupleInt, lambda x: OptionalTupleInt.none)
 converter(TupleInt, OptionalTupleInt, lambda x: OptionalTupleInt.some(x))
+# TODO: Don't allow ints to be converted to OptionalTupleInt, and have another type that also unions ints
 converter(int, OptionalTupleInt, lambda x: OptionalTupleInt.some(TupleInt(Int(x))))
 
 

diff --git a/python/egglog/runtime.py b/python/egglog/runtime.py
@@ -70,7 +70,41 @@ def converter(from_type: Type[T], to_type: Type[V], fn: Callable[[T], V]) -> Non
     to_type_name = process_tp(to_type)
     if not isinstance(to_type_name, JustTypeRef):
         raise TypeError(f"Expected return type to be a egglog type, got {to_type_name}")
-    CONVERSIONS[(process_tp(from_type), to_type_name)] = fn
+    _register_converter(process_tp(from_type), to_type_name, fn)
+
+
+def _register_converter(a: Type | JustTypeRef, b: JustTypeRef, a_b: Callable) -> None:
+    """
+    Registers a converter from some type to an egglog type, if not already registered.
+
+    Also adds transitive converters, i.e. if registering A->B and there is already B->C, then A->C will be registered.
+    Also, if registering A->B and there is already D->A, then D->B will be registered.
+    """
+    if a == b or (a, b) in CONVERSIONS:
+        return
+    CONVERSIONS[(a, b)] = a_b
+    for (c, d), c_d in list(CONVERSIONS.items()):
+        if b == c:
+            _register_converter(a, d, _ComposedConverter(a_b, c_d))
+        if a == d:
+            _register_converter(c, b, _ComposedConverter(c_d, a_b))
+
+
+@dataclass
+class _ComposedConverter:
+    """
+    A converter which is composed of multiple converters.
+
+    _ComposeConverter(a_b, b_c) is equivalent to lambda x: b_c(a_b(x))
+
+    We use the dataclass instead of the lambda to make it easier to debug.
+    """
+
+    a_b: Callable
+    b_c: Callable
+
+    def __call__(self, x: object) -> object:
+        return self.b_c(self.a_b(x))
 
 
 def convert(source: object, target: type[V]) -> V:

diff --git a/python/tests/test_convert.py b/python/tests/test_convert.py
@@ -1,6 +1,17 @@
+import copy
+
+import egglog.runtime
+import pytest
 from egglog import *
 
 
+@pytest.fixture(autouse=True)
+def reset_conversions():
+    old_conversions = copy.copy(egglog.runtime.CONVERSIONS)
+    yield
+    egglog.runtime.CONVERSIONS = old_conversions
+
+
 def test_conversion_custom_metaclass():
     class MyMeta(type):
         pass
@@ -33,3 +44,70 @@ def __init__(self):
     converter(MyType, MyTypeExpr, lambda x: MyTypeExpr())
 
     assert expr_parts(convert(MyType(), MyTypeExpr)) == expr_parts(MyTypeExpr())
+
+
+def test_conversion_transitive_forward():
+    egraph = EGraph()
+
+    class MyType:
+        pass
+
+    @egraph.class_
+    class MyTypeExpr(Expr):
+        def __init__(self):
+            ...
+
+    @egraph.class_
+    class MyTypeExpr2(Expr):
+        def __init__(self):
+            ...
+
+    converter(MyType, MyTypeExpr, lambda x: MyTypeExpr())
+    converter(MyTypeExpr, MyTypeExpr2, lambda x: MyTypeExpr2())
+
+    assert expr_parts(convert(MyType(), MyTypeExpr2)) == expr_parts(MyTypeExpr2())
+
+
+def test_conversion_transitive_backward():
+    egraph = EGraph()
+
+    class MyType:
+        pass
+
+    @egraph.class_
+    class MyTypeExpr(Expr):
+        def __init__(self):
+            ...
+
+    @egraph.class_
+    class MyTypeExpr2(Expr):
+        def __init__(self):
+            ...
+
+    converter(MyTypeExpr, MyTypeExpr2, lambda x: MyTypeExpr2())
+    converter(MyType, MyTypeExpr, lambda x: MyTypeExpr())
+    assert expr_parts(convert(MyType(), MyTypeExpr2)) == expr_parts(MyTypeExpr2())
+
+
+def test_conversion_transitive_cycle():
+    egraph = EGraph()
+
+    class MyType:
+        pass
+
+    @egraph.class_
+    class MyTypeExpr(Expr):
+        def __init__(self):
+            ...
+
+    @egraph.class_
+    class MyTypeExpr2(Expr):
+        def __init__(self):
+            ...
+
+    converter(MyType, MyTypeExpr, lambda x: MyTypeExpr())
+    converter(MyTypeExpr, MyTypeExpr2, lambda x: MyTypeExpr2())
+    converter(MyTypeExpr2, MyTypeExpr, lambda x: MyTypeExpr())
+
+    assert expr_parts(convert(MyType(), MyTypeExpr2)) == expr_parts(MyTypeExpr2())
+    assert expr_parts(convert(MyType(), MyTypeExpr)) == expr_parts(MyTypeExpr())