From c4ceed4411eed9761c0c6787525d32c2b404c292 Mon Sep 17 00:00:00 2001
From: "Alex A. Naanou" <alex.nanou@gmail.com>
Date: Sun, 2 Nov 2008 14:28:01 +0300
Subject: [PATCH] added pli.logictypes.AT...

---
 pli/logictypes.py | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/pli/logictypes.py b/pli/logictypes.py
index ce0f91a..9042fee 100755
--- a/pli/logictypes.py
+++ b/pli/logictypes.py
@@ -1,7 +1,7 @@
 #=======================================================================
 
 __version__ = '''0.1.21'''
-__sub_version__ = '''20081004173331'''
+__sub_version__ = '''20081102142629'''
 __copyright__ = '''(c) Alex A. Naanou 2003'''
 
 __doc__ = '''\
@@ -159,6 +159,43 @@ class IN(Pattern):
 		return self.container != other or self.obj not in other
 
 
+#------------------------------------------------------------------AT---
+class AT(Pattern):
+	'''
+	AT(A, B) == X iff A in X and X[B] == A
+
+	NOTE: this works as good as python's containers accept patterns.
+		  this mostly amounts to staying clear of using patterns as 
+		  indexes.
+	'''
+	def __init__(self, obj, position=ANY):
+		self.obj = obj
+		self.position = position
+	def __repr__(self):
+		return 'AT(%r, %r)' % (self.obj, self.position)
+	def __eq__(self, other):
+		try:
+			if other == SEQUENCE:
+				return self.obj in other \
+						and other[self.position] == self.obj
+			else:
+				# mappings...
+				return self.obj in other.values() \
+						and other[self.position] == self.obj
+		except (KeyError, IndexError):
+			return False
+	def __ne__(self, other):
+		try:
+			if other == SEQUENCE:
+				return self.obj not in other \
+						or other[self.position] != self.obj
+			else:
+				return self.obj not in other.values() \
+						or other[self.position] != self.obj
+		except (KeyError, IndexError):
+			return False
+
+
 
 #-----------------------------------------------------------------------
 # this is to define basic pattern combination mathematics.
@@ -874,6 +911,10 @@ if __name__ == '__main__':
 	print OR((1, ANY), (ANY, 2)) == (1, 8)
 	print OR((1, ANY), (ANY, 2)) != (7, 8)
 
+	print AT(1, 10) == range(100)
+	print AT(10, 10) == range(100)
+
+
 
 #=======================================================================
 #                                            vim:set ts=4 sw=4 nowrap :
-- 
2.11.4.GIT