diff --git a/advent/parser/parser.py b/advent/parser/parser.py
index 9772844..057136b 100644
--- a/advent/parser/parser.py
+++ b/advent/parser/parser.py
@@ -3,7 +3,7 @@ from __future__ import annotations
 from dataclasses import dataclass
 from functools import reduce
 from itertools import chain
-from typing import Any, Callable, Generic, Self, TypeVar, overload
+from typing import Any, Callable, Generic, Iterator, Self, TypeVar, overload
 import unicodedata
 
 from .result import Result
@@ -42,7 +42,7 @@ class ParserInput:
         return f'{self.input[self.start-3:self.start-1]}->[{self.input[self.start:]}]'
 
 
-ParserResult = Result[tuple[ParserInput, T]]
+ParserResult = Iterator[tuple[ParserInput, T]]
 ParserFunc = Callable[[ParserInput], ParserResult[T]]
 
 
@@ -51,16 +51,30 @@ class P(Generic[T]):
         self.func = func
 
     def parse(self, s: str, i: int = 0) -> Result[T]:
-        result = self.func(ParserInput(s, i))
-        return result.fmap(lambda pr: pr[1])
+        all_results = self.func(ParserInput(s, i))
+        try:
+            _, result = next(all_results)
+            return Result.of(result)
+        except StopIteration:
+            return Result.fail("No result")
+
+    def parse_multi(self, s: str, i: int = 0) -> Iterator[T]:
+        return (v for _, v in self.func(ParserInput(s, i)))
 
     @staticmethod
     def pure(value: T) -> P[T]:
-        return P(lambda parserPos: Result.of((parserPos, value)))
+        def inner(parserPos: ParserInput) -> ParserResult[T]:
+            yield (parserPos, value)
+        return P(inner)
 
     @staticmethod
-    def fail(text: str) -> P[Any]:
-        return P(lambda pp: Result.fail(f'@: {pp}\ntext: {text}'))
+    def fail() -> P[Any]:
+        def inner(_: ParserInput) -> ParserResult[Any]:
+            if False:
+                yield
+            pass
+
+        return P(inner)
 
     @staticmethod
     def _fix(p1: Callable[[P[Any]], P[T]]) -> P[T]:
@@ -72,24 +86,22 @@ class P(Generic[T]):
         return self
 
     def bind(self, bind_func: Callable[[T], P[TR]]) -> P[TR]:
-        def inner(x: tuple[ParserInput, T]):
-            parserPos, v = x
-            return bind_func(v).func(parserPos)
-
-        return P(lambda parserPos: self.func(parserPos).bind(inner))
+        def inner(parserPos: ParserInput) -> ParserResult[TR]:
+            return (r for rs in (bind_func(v).func(pp)
+                    for pp, v in self.func(parserPos)) for r in rs)
+        return P(inner)
 
     def fmap(self, map_func: Callable[[T], TR]) -> P[TR]:
-        def inner(x: tuple[ParserInput, T]):
-            parserPos, v = x
-            return (parserPos, map_func(v))
-        return P(lambda parserPos: self.func(parserPos).fmap(inner))
+        def inner(parserPos: ParserInput) -> ParserResult[TR]:
+            return ((pp, map_func(v)) for pp, v in self.func(parserPos))
+        return P(inner)
 
     def safe_fmap(self, map_func: Callable[[T], TR]) -> P[TR]:
         def inner(value: T) -> P[TR]:
             try:
                 return P.pure(map_func(value))
-            except Exception as e:
-                return P.fail(f'Failed with {e}')
+            except Exception:
+                return P.fail()
         return self.bind(inner)
 
     def replace(self, value: TR) -> P[TR]:
@@ -115,8 +127,7 @@ class P(Generic[T]):
         return P.either(self.some(), P.pure([]))
 
     def satisfies(self, pred: Callable[[T], bool], failtext: str) -> P[T]:
-        return self.bind(lambda v: P.pure(v) if pred(
-            v) else P.fail(f'Does not satisfy: {failtext}'))
+        return self.bind(lambda v: P.pure(v) if pred(v) else P.fail())
 
     def optional(self) -> P[T | None]:
         return P.either(self, P.pure(None))
@@ -133,13 +144,15 @@ class P(Generic[T]):
         return P.map2(p1, p2, lambda v1, _: v1)
 
     @staticmethod
-    def no_match(p: P[Any], failtext: str) -> P[tuple[()]]:
-        def inner(pp: ParserInput) -> ParserResult[tuple[()]]:
-            result = p.func(pp)
-            if result.is_fail():
-                return Result.of((pp, ()))
-            else:
-                return Result.fail(failtext)
+    def no_match(p: P[Any]) -> P[tuple[()]]:
+        def inner(parserPos: ParserInput) -> ParserResult[tuple[()]]:
+            result = p.func(parserPos)
+            try:
+                next(result)
+                # Silently yields nothing so is an empty Generator
+            except StopIteration:
+                yield (parserPos, ())
+
         return P(inner)
 
     @ staticmethod
@@ -233,8 +246,8 @@ class P(Generic[T]):
     @ staticmethod
     def either(p1: P[T1], p2: P[T2], /) -> P[T1 | T2]:
         def inner(parserPos: ParserInput):
-            result = p1.func(parserPos)
-            return result if result.is_ok() else p2.func(parserPos)
+            yield from p1.func(parserPos)
+            yield from p2.func(parserPos)
 
         return P(inner)
 
@@ -256,7 +269,7 @@ class P(Generic[T]):
 
     @ staticmethod
     def choice(*ps: P[Any]) -> P[Any]:
-        return reduce(P.either, ps, P.fail('No Choice matched'))
+        return reduce(P.either, ps, P.fail())
 
     @ staticmethod
     def choice_same(*ps: P[T]) -> P[T]:
@@ -264,12 +277,17 @@ class P(Generic[T]):
 
     @ staticmethod
     def any_char() -> P[str]:
-        return P(lambda pp: Result.of(pp.step()) if not pp.is_eof()
-                 else Result.fail('At EOF'))
+        def inner(parserPos: ParserInput) -> ParserResult[str]:
+            if not parserPos.is_eof():
+                yield parserPos.step()
+        return P(inner)
 
     @ staticmethod
     def eof() -> P[tuple[()]]:
-        return P.no_match(P.any_char(), 'Not at eof')
+        def inner(parserPos: ParserInput) -> ParserResult[tuple[()]]:
+            if parserPos.is_eof():
+                yield parserPos, ()
+        return P(inner)
 
     @ staticmethod
     def is_char(cmp: str) -> P[str]:
@@ -277,7 +295,7 @@ class P(Generic[T]):
 
     @staticmethod
     def is_not_char(s: str) -> P[tuple[()]]:
-        return P.no_match(P.is_char(s), f'Did match {s}')
+        return P.no_match(P.is_char(s))
 
     @ staticmethod
     def char_by_func(cmp: Callable[[str], bool], failtext: str) -> P[str]:
@@ -298,12 +316,12 @@ class P(Generic[T]):
     @ staticmethod
     def is_decimal(num: int) -> P[str]:
         return P.any_decimal().bind(
-            lambda c: P.pure(c) if unicodedata.decimal(c) == num else P.fail(f'Not {num}'))
+            lambda c: P.pure(c) if unicodedata.decimal(c) == num else P.fail())
 
     @ staticmethod
     def is_not_decimal(num: int) -> P[str]:
         return P.any_decimal().bind(
-            lambda c: P.pure(c) if unicodedata.decimal(c) != num else P.fail(f'Is {num}'))
+            lambda c: P.pure(c) if unicodedata.decimal(c) != num else P.fail())
 
     @ staticmethod
     def lower() -> P[str]:
@@ -323,7 +341,7 @@ class P(Generic[T]):
 
     @ staticmethod
     def unsigned() -> P[int]:
-        return P.either(P.fst(P.is_decimal(0), P.no_match(P.any_decimal(), 'starting Zero')),
+        return P.either(P.fst(P.is_decimal(0), P.no_match(P.any_decimal())),
                         P.map2(P.is_not_decimal(0), P.any_decimal().many(),
                                lambda f, s: f + ''.join(s))
                         ).fmap(int)
diff --git a/advent/parser/test_parser.py b/advent/parser/test_parser.py
index f2c0c8b..779b45a 100644
--- a/advent/parser/test_parser.py
+++ b/advent/parser/test_parser.py
@@ -130,7 +130,7 @@ def test_seq_seq():
 
 def test_not():
     input = 'a'
-    parser = P.snd(P.no_match(P.is_char('!'), 'found !'), P.is_char('a'))
+    parser = P.snd(P.no_match(P.is_char('!')), P.is_char('a'))
     expected = 'a'
     result = parser.parse(input).get()
     assert result == expected
@@ -138,3 +138,30 @@ def test_not():
     input2 = '!'
     result2 = parser.parse(input2)
     assert result2.is_fail()
+
+
+def test_multi():
+    input = 'aa'
+    parser = P.is_char('a').many()
+    expected = [['a', 'a'], ['a'], []]
+    result = list(parser.parse_multi(input))
+    assert result == expected
+
+
+def test_either():
+    input = 'aab'
+    parser = P.either(
+        P.seq(
+            P.is_char('a').many(), P.string('b')), P.seq(
+            P.string('a'), P.string('ab')))
+    expected = [(['a', 'a'], 'b'), ('a', 'ab')]
+    result = list(parser.parse_multi(input))
+    assert result == expected
+
+
+def test_seq_eof():
+    input = 'aa'
+    parser = P.seq(P.is_char('a').many(), P.eof())
+    expected = [(['a', 'a'], ())]
+    result = list(parser.parse_multi(input))
+    assert result == expected