Data commit

Task/Multisplit/Python/multisplit-4.py

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+'''Multisplit'''
+
+
+from functools import reduce
+
+
+# multiSplit :: [String] -> String -> [(String, String, Int)]
+def multiSplit(separators):
+    '''List of triples:
+       [(token, separator, start index of separator].
+    '''
+    def go(s):
+        def f(tokensPartsOffset, ic):
+            tokens, parts, offset = tokensPartsOffset
+            i, c = ic
+            inDelim = offset > i
+            return maybe(
+                (
+                    tokens if inDelim
+                    else c + tokens, parts, offset
+                )
+            )(
+                lambda x: (
+                    '',
+                    [(tokens, x, i)] + parts,
+                    i + len(x)
+                )
+            )(
+                None if inDelim else find(
+                    s[i:].startswith
+                )(separators)
+            )
+        ts, ps, _ = reduce(f, enumerate(s), ('', [], 0))
+        return list(reversed(ps)) + [(ts, '', len(s))]
+    return go
+
+
+# ------------------------- TEST -------------------------
+# main :: IO ()
+def main():
+    '''String split on three successive separators.'''
+    print(
+        multiSplit(['==', '!=', '='])(
+            'a!===b=!=c'
+        )
+    )
+
+
+# ------------------ GENERIC FUNCTIONS -------------------
+
+# find :: (a -> Bool) -> [a] -> (a | None)
+def find(p):
+    '''Just the first element in the list that matches p,
+       or None if no elements match.
+    '''
+    def go(xs):
+        try:
+            return next(x for x in xs if p(x))
+        except StopIteration:
+            return None
+    return go
+
+
+# maybe :: b -> (a -> b) -> (a | None) -> b
+def maybe(v):
+    '''Either the default value v, if m is None,
+       or the application of f to x.
+    '''
+    return lambda f: lambda m: v if (
+        None is m
+    ) else f(m)
+
+
+# MAIN ---
+if __name__ == '__main__':
+    main()