Added style #18. Srsly.

18-reflective/README.md

@@ -0,0 +1,16 @@
+Style #18
+==============================
+
+Constraints:
+
+- The program has access to information about itself, i.e. introspection
+
+- The program can modify itself -- adding more abstractions, variables, etc. at run-time
+
+
+Possible names:
+
+- Reflective, as in "I see me, so I can change myself"
+- Metaprogramming style
+- Self-referential
+

18-reflective/tf-18.py

@@ -0,0 +1,55 @@
+#!/usr/bin/env python
+
+import sys, re, operator, string
+
+#
+# Two down-to-earth things that cannot be reflected on
+# without serious performance penalties
+#
+stops = set(open("../stop_words.txt").read().split(",") + list(string.ascii_lowercase))
+
+def frequencies_imp(word_list):
+    """
+    Takes a list of words and returns a dictionary associating
+    words with frequencies of occurrence
+    """
+    word_freqs = {}
+    for w in word_list:
+        if w in word_freqs:
+            word_freqs[w] += 1
+        else:
+            word_freqs[w] = 1
+    return word_freqs
+
+#
+# Let's write our function bodies as strings.
+# Because we're looking at them from "above"
+#
+extract_words_func_body = "lambda name : [x.lower() for x in re.split('[^a-zA-Z]+', open(name).read()) if len(x) > 0 and x.lower() not in stops]"
+
+frequencies_func_body = "lambda word_list : frequencies_imp(word_list)"
+
+sort_func_body = "lambda word_freq: sorted(word_freq.iteritems(), key=operator.itemgetter(1), reverse=True)"
+
+#
+# So far, this program isn't much about term-frequency. It's about
+# a bunch of strings that look like function bodies.
+# Let's add our functions to the "base" program, dynamically.
+# We're re-writing this program by adding more functions to it
+# from "above".
+#
+exec('extract_words = ' + extract_words_func_body)
+exec('frequencies = ' + frequencies_func_body)
+exec('sort = ' + sort_func_body)
+
+#
+# The main function. This would work just fine:
+#  word_freqs = sort(frequencies(extract_words(sys.argv[1])))
+# But because we're being introspective, we'll call the 
+# functions also from "above"
+#
+word_freqs = locals()['sort'](locals()['frequencies'](locals()['extract_words'](sys.argv[1])))
+
+for tf in word_freqs[0:25]:
+    print tf[0], ' - ', tf[1]
+