Stopped fixed-case tagging of "K" and "N" (acl-org#960)

Stopped fixed-case tagging of "K" and "N" because it resulted in marking of expressions like "N-gram" and "K-means"

Co-authored-by: Marc Schulder <>

bin/fixedcase/README.md

@@ -18,7 +18,7 @@ Fixed-caseness is determined by this decision list:
 4. Any word with a capital letter in a non-initial position (e.g.,
    "TextTiling", "QA") is fixed-case.
 5. The French contracted forms "L’" and "D’" are not fixed-case.
-6. Any tokenized word consisting of a single uppercase letter other than "A",
+6. Any tokenized word consisting of a single uppercase letter other than "A", "K" or "N",
    or a single uppercase letter plus ".", is fixed-case.
 7. If one of a short list of adjectival modifiers including "North" and "Modern"
    precedes a fixed-case word, optionally separated by a hyphen,

bin/fixedcase/common.py

@@ -49,7 +49,7 @@ def fixedcase_word(w, truelist=None):
     if any(c.isupper() for c in w[1:]):
         # tokenized word with noninitial uppercase
         return True
-    if len(w) == 1 and w.isupper() and w != 'A':
+    if len(w) == 1 and w.isupper() and w not in {'A', 'K', 'N'}:
         # single uppercase letter
         return True
     if len(w) == 2 and w[1] == '.' and w[0].isupper():