[Predator] Move ``SingleFeatureScore`` to LLM.

appengine/findit/crash/loglinear/feature.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 from collections import namedtuple
 import math
 
 import libs.math.logarithms as lmath
 
 
@@ skipping 120 matching lines @@
     thinks the ``y`` should be blamed or should not be depends on the sign
     of the value and the sign of the weight given to this feature.) As
     special cases, a value of negative infinity means "do not blame this
     ``y`` no matter what any other features say", and a value of positive
     infinity means "definitely blame this ``y`` no matter what any other
     features say". Both of those special values should be used sparingly,
     since they override the model's ability to combine multiple sources of
     information and decide the cuplrit based on all the evidence together.
     """
     raise NotImplementedError()
+
+
+class FeatureFunction(object):
+  """Given an iterable of scalar-valued functions, return an dict function.
+
+  Properties:
+    fs (iterable of functions): A collection of curried functions
+    ``X -> Y -> FeatureValue``. That is, given a particular ``x`` they
+    return a function ``Y -> dict(FeatureValue)``. N.B. each function should
+    have a name property.

[wrengr, 2017/01/25 21:54:27]

I still say it'd be clearer to refer to the ``Feature`` interface rather than
calling it a "function with a name property".

+  """
+  def __init__(self, fs):
+    self._fs = fs
+
+  def __call__(self, x):
+    """Fuction mapping ``X -> Y -> dict(FeatureValue.name to FeatureValue).
+
+    Returns:
+      A function ``X -> Y -> dict(FeatureValue.name to FeatureValue)`` where for 
+      all ``x``, ``y``, and for a feature f in fs, we have
+      ``FeatureFunction(fs)(x)(y)[f.name] == f(x)(y)``.
+    """
+    name_to_fx = {f.name: f(x) for f in self._fs}
+    return lambda y: {name: fx(y) for name, fx in name_to_fx.iteritems()}