Allow up to 5 inputs for add, subtract, multiply

This allows users to provide up to 5 inputs to each of `/maths add`,
`/maths subtract`, and `/maths multiply`. The third, fourth, and fifth
inputs are optional, and the user can pick whichever ones they want,
skip ones in between, etc. The code only uses the actually provided
values.

maths.py

@@ -1,3 +1,7 @@
+from functools import reduce
+from math import fsum, prod
+from operator import sub
+
 import discord
 from discord import app_commands
 from discord.ext import commands
@@ -13,25 +17,53 @@ def __init__(self, bot: DTbot):
         self.bot = bot
 
     @app_commands.command(description="Add two numbers together")
-    async def add(self, interaction: discord.Interaction, first: float, second: float):
-        first = rint(first, digits=3)
-        second = rint(second, digits=3)
-        result = rint(first + second, digits=3)
-        await interaction.response.send_message(f"{first:,} + {second:,} = {result:,}")
+    async def add(
+        self,
+        interaction: discord.Interaction,
+        first: float,
+        second: float,
+        third: float | None,
+        fourth: float | None,
+        fifth: float | None,
+    ):
+        raw_inputs = [first, second, third, fourth, fifth]
+        numbers = [rint(num, digits=3) for num in raw_inputs if num is not None]
+        strs = [f"({i:,})" if i < 0 else f"{i:,}" for i in numbers]
+        result = rint(fsum(numbers), digits=3)
+        await interaction.response.send_message(f"{' + '.join(strs)} = {result:,}")
 
     @app_commands.command(description="Subtract two numbers")
-    async def subtract(self, interaction: discord.Interaction, first: float, second: float):
-        first = rint(first, digits=3)
-        second = rint(second, digits=3)
-        result = rint(first - second, digits=3)
-        await interaction.response.send_message(f"{first:,} - {second:,} = {result:,}")
+    async def subtract(
+        self,
+        interaction: discord.Interaction,
+        first: float,
+        second: float,
+        third: float | None,
+        fourth: float | None,
+        fifth: float | None,
+    ):
+        raw_inputs = [first, second, third, fourth, fifth]
+        numbers = [rint(num, digits=3) for num in raw_inputs if num is not None]
+        strs = [f"({i:,})" if i < 0 else f"{i:,}" for i in numbers]
+        result = rint(reduce(sub, numbers), digits=3)  # type: ignore
+        await interaction.response.send_message(f"{' - '.join(strs)} = {result:,}")
 
     @app_commands.command(description="Multiply two numbers")
-    async def multiply(self, interaction: discord.Interaction, first: float, second: float):
-        first = rint(first, digits=3)
-        second = rint(second, digits=3)
-        result = rint(first * second, digits=3)
-        await interaction.response.send_message(f"{first:,} * {second:,} = {result:,}")
+    async def multiply(
+        self,
+        interaction: discord.Interaction,
+        first: float,
+        second: float,
+        third: float | None,
+        fourth: float | None,
+        fifth: float | None,
+    ):
+        raw_inputs = [first, second, third, fourth, fifth]
+        numbers = [rint(num, digits=3) for num in raw_inputs if num is not None]
+        strs = [f"({i:,})" if i < 0 else f"{i:,}" for i in numbers]
+        result = rint(prod(numbers), digits=3)
+        escaped_asterisk = " \\* "  # Prevent Discord Markdown rendering (f-strings disallow escape sequences in <3.12)
+        await interaction.response.send_message(f"{escaped_asterisk.join(strs)} = {result:,}")
 
     @app_commands.command(description="Divide a number by another number")
     async def divide(self, interaction: discord.Interaction, dividend: float, divisor: float):