Added style #24, quarantine, inspired by IO Monad constraints

24-quarantine/README.md

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+Style #9
+==============================
+
+Constraints:
+
+- Core program functions have no side effects of any kind, inlcuding IO
+
+- All IO actions must be contained in computation sequences that are
+  clearly separated from the pure functions
+
+- All sequences that have IO must be called from the main program
+
+Possible names:
+
+- Quarantine
+- Monadic IO
+- Imperative functional style

24-quarantine/tf-24.py

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+#!/usr/bin/env python
+import sys, re, operator, string
+
+#
+# The Quarantine class for this example
+#
+class TFQuarantine:
+    def __init__(self):
+        self._funcs = []
+
+    def bind(self, func):
+        self._funcs.append(func)
+        return self
+
+    def execute(self):
+        value = lambda : None
+        for func in self._funcs:
+            value = func(value())
+        print value()
+
+#
+# The functions
+#
+def get_input(arg):
+    def _f():
+        return sys.argv[1]
+    return _f
+
+def read_file(path_to_file):
+    def _f():
+        with open(path_to_file) as f:
+            data = f.read()
+        return data
+    return _f
+
+def filter_chars(str_data):
+    def _f():
+        pattern = re.compile('[\W_]+')
+        return pattern.sub(' ', str_data)
+    return _f
+
+def normalize(str_data):
+    def _f():
+        return str_data.lower()
+    return _f
+
+def scan(str_data):
+    def _f():
+        return str_data.split()
+    return _f
+
+def remove_stop_words(word_list):
+    def _f():
+        with open('../stop_words.txt') as f:
+            stop_words = f.read().split(',')
+        # add single-letter words
+        stop_words.extend(list(string.ascii_lowercase))
+        return [w for w in word_list if not w in stop_words]
+    return _f
+
+def frequencies(word_list):
+    def _f():
+        word_freqs = {}
+        for w in word_list:
+            if w in word_freqs:
+                word_freqs[w] += 1
+            else:
+                word_freqs[w] = 1
+        return word_freqs
+    return _f
+
+def sort(word_freq):
+    def _f():
+        return sorted(word_freq.iteritems(), key=operator.itemgetter(1), reverse=True)
+    return _f
+
+def top25_freqs(word_freqs):
+    def _f():
+        top25 = ""
+        for tf in word_freqs[0:25]:
+            top25 += str(tf[0]) + ' - ' + str(tf[1]) + '\n'
+        return top25
+    return _f
+
+#
+# The main function
+#
+quarantine = TFQuarantine()
+quarantine.bind(get_input).bind(read_file).bind(filter_chars).bind(normalize).bind(scan).bind(remove_stop_words).bind(frequencies).bind(sort).bind(top25_freqs)
+quarantine.execute()
+