add as_a

Author: czheo

README.md

@@ -158,15 +158,15 @@ from syntax_sugar import INF, take, each
 for i in 1 /to/ INF:
     print(i)
 
-list(1 /to/ INF /take/ 5)
+1 /to/ INF /take/ 5 /as_a/ list
 # there is a `take` functon which is similar to itertools.islice
 # return [1, 2, 3, 4, 5]
 
-list(0 /to/ -INF /step/ 2 /take/ 5)
+0 /to/ -INF /step/ 2 /take/ 5 /as_a/ list
 # also works with negative infinity.
 # return [0, -2, -4, -6, -8]
 
-list((1 /to/ 3) * (4 /to/ 6))
+(1 /to/ 3) * (4 /to/ 6) /as_a/ list
 # all combinations of [1..3] * [4..6]
 # return [(1, 4), (1, 5), (1, 6), (2, 4), (2, 5), (2, 6), (3, 4), (3, 5), (3, 6)]
 
@@ -188,6 +188,20 @@ def push(lst, x):
 [] /push/ 1 /push/ 2 /push/ 3
 # returns [1,2,3]
 ```
+
+You can also do
+
+```
+def push(lst, x):
+    lst.append(x)
+    return lst
+
+ipush = push /as_a/ infix
+
+[] /ipush/ 1 /ipush/ 2 /ipush/ 3
+# returns [1,2,3]
+```
+
 <!---
 ### stream
 

syntax_sugar/infix.py

@@ -4,6 +4,7 @@
 __all__ = [
     'infix',
     'is_a',
+    'as_a',
     'to',
     'step',
     'INF',
@@ -26,29 +27,26 @@ def __rtruediv__(self, left):
 is_a = infix(isinstance)
 has = infix(hasattr)
 
+@infix
+def as_a(obj, clazz):
+    return clazz(obj)
+
 @infix
 def to(start, end):
     return Iterator(Range(start, end))
 
 @infix
 def step(obj, step):
-    # ex. -2 step -> 2 step
     step = abs(step)
     obj = Iterator(obj) if not obj /is_a/ Iterator else obj
     return obj.slice(step=step)
 
 @infix
 def take(obj, n):
-    # ex. n = 3
-    # [0, 1, 2, 3, 4, 5, 6] =>
-    # [0, 1, 2]
     obj = Iterator(obj) if not obj /is_a/ Iterator else obj
     return obj.slice(stop=n)
 
 @infix
 def drop(obj, n):
-    # ex. n = 3
-    # [0, 1, 2, 3, 4, 5, 6] =>
-    # [3, 4, 5, 6]
     obj = Iterator(obj) if not obj /is_a/ Iterator else obj
     return obj.slice(start=n)

tests/test_infix.py

@@ -112,3 +112,6 @@ def test_is_a():
     for value, types in values_types_wrong:
         for type in types:
             assert not value /is_a/ type
+
+def test_as_a():
+    assert 1 /as_a/ str == '1'