Merge pull request #61 from Yelp/adds-sequence-helper-func

Adds `sequence` helper function; closes #59

docs/source/util.rst

@@ -53,6 +53,10 @@ Modifies a grammar element to print the tokens that it matches.
 
 Modifies a grammar element to parse to the result of calling `action` on the  tokens produced by that grammar element.
 
+**sequence(grammar, n)**
+
+Creates a grammar element that matches exactly `n` of the input grammar.
+
 `undebt.pattern.common`
 -----------------------
 

tests/pattern/util_test.py

@@ -7,12 +7,14 @@
 
 import mock
 from pyparsing import Keyword
+from pyparsing import Literal
 
 from undebt.pattern.testing import assert_parse
 from undebt.pattern.util import debug
 from undebt.pattern.util import in_string
 from undebt.pattern.util import leading_whitespace
 from undebt.pattern.util import quoted
+from undebt.pattern.util import sequence
 from undebt.pattern.util import trailing_whitespace
 
 
@@ -73,3 +75,14 @@ def test_in_string():
     assert in_string(7, test)
     assert in_string(8, test)
     assert not in_string(9, test)
+
+
+def test_sequence():
+    a = Literal('a')
+    double_a = sequence(a, n=2)
+    triple_a = sequence(a, n=3)
+
+    assert double_a.matches('aa')
+    assert triple_a.matches('aaa')
+    assert not double_a.matches('aaa')
+    assert not triple_a.matches('aa')

undebt/__init__.py

@@ -6,4 +6,4 @@
 
 # this should be the only place where the version is kept, if you
 # need to know the version somewhere else just import it from here
-__version__ = "0.6.1"
+__version__ = "0.6.2"

undebt/pattern/util.py

@@ -4,6 +4,7 @@
 from __future__ import print_function
 
 import functools
+import operator
 
 from pyparsing import _trim_arity
 from pyparsing import col
@@ -107,3 +108,11 @@ def new_replace(s, l, tokens):
             return _trim_arity(old_replace)(s, l, tokendict)
         return new_replace
     return decorator
+
+
+def sequence(grammar, n):
+    """
+    Creates a grammar element that matches exactly N of the input
+    grammar.
+    """
+    return functools.reduce(operator.add, [grammar] * n)