Split out example parsers into separate modules in the examples direc…

…tory.

CHANGES

@@ -32,6 +32,9 @@ plusminus Change Log
       using (), (], [) or [] notation ("in" with sets is still
       supported).
 
+    - Deleted the example_parsers.py module in the examples directory, and split
+      the parsers out into separate modules in that directory.
+
     - Added __version_info__ structure, following pattern of sys.version_info
       field names.
 

plusminus/examples/business_arithmetic_parser.py

@@ -0,0 +1,63 @@
+#
+# business_arithmetic_parser.py
+#
+# Copyright 2021, Paul McGuire
+#
+from plusminus import BaseArithmeticParser, safe_pow
+
+
+class BusinessArithmeticParser(BaseArithmeticParser):
+    """
+    A parser for evaluating common financial and retail calculations:
+
+        50% of 20
+        20 * (1-20%)
+        (100-20)% of 20
+        5 / 20%
+        FV(20000, 3%, 30)
+        FV(20000, 3%/12, 30*12)
+
+    Functions:
+        FV(present_value, rate_per_period, number_of_periods)
+            future value of an amount, n periods in the future, at an interest rate per period
+        PV(future_value, rate_per_period, number_of_periods)
+            present value of a future amount, n periods in the future, at an interest rate per period
+        PP(present_value, rate_per_period, number_of_periods)
+            periodic value of n amounts, one per period, for n periods, at an interest rate per period
+    """
+
+    def customize(self):
+        def pv(future_value, rate, n_periods):
+            return future_value / safe_pow(1 + rate, n_periods)
+
+        def fv(present_value, rate, n_periods):
+            return present_value * safe_pow(1 + rate, n_periods)
+
+        def pp(present_value, rate, n_periods):
+            return rate * present_value / (1 - safe_pow(1 + rate, -n_periods))
+
+        super().customize()
+        self.add_operator("of", 2, BaseArithmeticParser.LEFT, lambda a, b: a * b)
+        self.add_operator("%", 1, BaseArithmeticParser.LEFT, lambda a: a / 100)
+
+        self.add_function("PV", 3, pv)
+        self.add_function("FV", 3, fv)
+        self.add_function("PP", 3, pp)
+
+
+if __name__ == '__main__':
+
+    parser = BusinessArithmeticParser()
+    parser.runTests(
+        """\
+        25%
+        20 * 50%
+        50% of 20
+        20 * (1-20%)
+        (100-20)% of 20
+        5 / 20%
+        FV(20000, 3%, 30)
+        FV(20000, 3%/12, 30*12)
+        """,
+        postParse=lambda _, result: result[0].evaluate(),
+    )

plusminus/examples/combinatorics_arithmetic_parser.py

@@ -0,0 +1,50 @@
+#
+# combinatorics_arithmetic_parser.py
+#
+# Copyright 2021, Paul McGuire
+#
+from plusminus import BaseArithmeticParser, ArithmeticParser, constrained_factorial
+
+
+class CombinatoricsArithmeticParser(BaseArithmeticParser):
+    """
+    Parser for evaluating expressions of combinatorics problems, for numbers of
+    permutations (nPm) and combinations (nCm):
+
+        nPm = n! / (n-m)!
+        8P4 = number of (ordered) permutations of selecting 4 items from a collection of 8
+
+        nCm = n! / m!(n-m)!
+        8C4 = number of (unordered) combinations of selecting 4 items from a collection of 8
+    """
+
+    def customize(self):
+        super().customize()
+        # fmt: off
+        self.add_operator("P", 2, BaseArithmeticParser.LEFT,
+                          lambda a, b: int(constrained_factorial(a) / constrained_factorial(a - b)))
+        self.add_operator("C", 2, BaseArithmeticParser.LEFT,
+                          lambda a, b: int(constrained_factorial(a)
+                                           / constrained_factorial(b)
+                                           / constrained_factorial(a - b)))
+        self.add_operator(*ArithmeticParser.Operators.FACTORIAL)
+        # fmt: on
+
+
+if __name__ == '__main__':
+
+    parser = CombinatoricsArithmeticParser()
+    parser.runTests(
+        """\
+        3!
+        -3!
+        3!!
+        6! / (6-2)!
+        6 P 2
+        6! / (2!*(6-2)!)
+        6 C 2
+        6P6
+        6C6
+        """,
+        postParse=lambda _, result: result[0].evaluate(),
+    )

plusminus/examples/date_time_arithmetic_parser.py

@@ -0,0 +1,59 @@
+#
+# date_time_arithmetic_parser.py
+#
+# Copyright 2021, Paul McGuire
+#
+from plusminus import BaseArithmeticParser
+
+
+class DateTimeArithmeticParser(BaseArithmeticParser):
+    """
+    Parser for evaluating expressions in dates and times, using operators d, h, m, and s
+    to define terms for amounts of days, hours, minutes, and seconds:
+
+        now()
+        today()
+        now() + 10s
+        now() + 24h
+
+    All numeric expressions will be treated as UTC integer timestamps. To display
+    timestamps as ISO strings, use str():
+
+        str(now())
+        str(today() + 3d)
+    """
+
+    SECONDS_PER_MINUTE = 60
+    SECONDS_PER_HOUR = SECONDS_PER_MINUTE * 60
+    SECONDS_PER_DAY = SECONDS_PER_HOUR * 24
+
+    def customize(self):
+        from datetime import datetime
+
+        # fmt: off
+        self.add_operator("d", 1, BaseArithmeticParser.LEFT, lambda t: t * DateTimeArithmeticParser.SECONDS_PER_DAY)
+        self.add_operator("h", 1, BaseArithmeticParser.LEFT, lambda t: t * DateTimeArithmeticParser.SECONDS_PER_HOUR)
+        self.add_operator("m", 1, BaseArithmeticParser.LEFT, lambda t: t * DateTimeArithmeticParser.SECONDS_PER_MINUTE)
+        self.add_operator("s", 1, BaseArithmeticParser.LEFT, lambda t: t)
+
+        self.add_function("now", 0, lambda: datetime.utcnow().timestamp())
+        self.add_function("today", 0,
+                          lambda: datetime.utcnow().replace(hour=0, minute=0, second=0, microsecond=0).timestamp())
+        self.add_function("str", 1, lambda dt: str(datetime.fromtimestamp(dt)))
+        # fmt: on
+
+
+if __name__ == "__main__":
+
+    parser = DateTimeArithmeticParser()
+    parser.runTests(
+        """\
+        now()
+        str(now())
+        str(today())
+        "A day from now: " + str(now() + 1d)
+        "A day and an hour from now: " + str(now() + 1d + 1h)
+        str(now() + 3*(1d + 1h))
+        """,
+        postParse=lambda _, result: result[0].evaluate(),
+    )

plusminus/examples/dice_roll_parser.py

@@ -0,0 +1,40 @@
+#
+# dice_roll_parser.py
+#
+# Copyright 2021, Paul McGuire
+#
+from plusminus import BaseArithmeticParser
+
+
+class DiceRollParser(BaseArithmeticParser):
+    """
+    Parser for evaluating expressions representing rolls of dice, as used in many board and
+    role-playing games, such as:
+
+        d20
+        3d20
+        5d6 + d20
+    """
+
+    def customize(self):
+        import random
+
+        # fmt: off
+        self.add_operator("d", 1, BaseArithmeticParser.RIGHT, lambda a: random.randint(1, a))
+        self.add_operator("d", 2, BaseArithmeticParser.LEFT,
+                          lambda a, b: sum(random.randint(1, b) for _ in range(a)))
+        # fmt: on
+
+
+if __name__ == '__main__':
+
+    parser = DiceRollParser()
+    parser.runTests(
+        """\
+        d20
+        3d6
+        d20+3d4
+        2d100
+        """,
+        postParse=lambda _, result: result[0].evaluate(),
+    )