Add Fate die support

README.md

@@ -54,7 +54,7 @@ These are the atoms used at the base of the syntax tree.
 | Name    | Syntax                            | Description           | Examples                       |
 |---------|-----------------------------------|-----------------------|--------------------------------|
 | literal | `INT`, `DECIMAL`                  | A literal number.     | `1`, `0.5`, `3.14`             |
-| dice    | `INT? "d" (INT \| "%")`           | A set of die.         | `d20`, `3d6`                   |
+| dice    | `INT? "d" (INT \| "%" \| "F" \| "f")` | A set of die.         | `d20`, `3d6`                   |
 | set     | `"(" (num ("," num)* ","?)? ")"`  | A set of expressions. | `()`, `(2,)`, `(1, 3+3, 1d20)` |
 
 Note that `(3d6)` is equivalent to `3d6`, but `(3d6,)` is the set containing the one element `3d6`.

d20/diceast.py

@@ -428,6 +428,8 @@ def __init__(self, num, size):
         self.num = int(num)
         if str(size) == "%":
             self.size = str(size)
+        elif str(size) == "F" or str(size) == "f":
+            self.size = "F"
         else:
             self.size = int(size)
 

d20/expression.py

@@ -175,6 +175,18 @@ def __repr__(self):
         return f"<Literal {self.number}>"
 
 
+class FateLiteral(Literal):
+    """A literal for Fate dice"""
+
+    def __repr__(self):
+        if self.number == -1:
+            return "<FateLiteral ->"
+        elif self.number == 0:
+            return "<FateLiteral 0>"
+        else:
+            return "<FateLiteral +>"
+
+
 class UnOp(Number):
     """Represents a unary operation."""
 
@@ -416,12 +428,14 @@ def children(self):
         return []
 
     def _add_roll(self):
-        if self.size != "%" and self.size < 1:
+        if self.size != "%" and self.size != "F" and self.size < 1:
             raise errors.RollValueError("Cannot roll a 0-sided die.")
         if self._context:
             self._context.count_roll()
         if self.size == "%":
             n = Literal(random.randrange(10) * 10)
+        if self.size == "F":
+            n = FateLiteral(random.choice([-1, 0, 1])) # Technically it's -/0/+, but this also works with 4dF
         else:
             n = Literal(random.randrange(self.size) + 1)  # 200ns faster than randint(1, self._size)
         self.values.append(n)

d20/grammar.lark

@@ -46,7 +46,7 @@ DICE_OPERATOR: "rr" | "ro" | "ra" | "e" | "mi" | "ma"
 
 diceexpr: INTEGER? "d" DICE_VALUE
 
-DICE_VALUE: INTEGER | "%"
+DICE_VALUE: INTEGER | "%" | "F" | "f"
 
 selector: [SELTYPE] INTEGER
 

tests/test_dice.py

@@ -5,6 +5,8 @@
 STANDARD_EXPRESSIONS = [
     "1d20",
     "1d%",
+    "1dF",
+    "1df"
     "1+1",
     "4d6kh3",
     "(1)",
@@ -13,6 +15,7 @@
     "4*(3d8kh2+9[fire]+(9d2e2+3[cold])/2)",
     "(1d4, 2+2, 3d6kl1)kh1",
     "((10d6kh5)kl2)kh1",
+    "17dFkh3"
 ]
 
 
@@ -46,6 +49,7 @@ def test_sane_totals():
         assert 1 <= r("(((1d6)))") <= 6
         assert 4 <= r("(1d4, 2+2, 3d6kl1)kh1") <= 6
         assert 1 <= r("((10d6kh5)kl2)kh1") <= 6
+        assert -1 <= r("1dF") <= 1
 
 
 def test_pemdas():