From 011fcf828ebd1325dbd4dfa21c4952f1be38a29f Mon Sep 17 00:00:00 2001
From: Nathan Perry <np@nathanperry.dev>
Date: Tue, 6 Aug 2024 12:51:38 -0400
Subject: roll: fixup for pratt parser

---
 src/commands/roll.rs | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/src/commands/roll.rs b/src/commands/roll.rs
index 6cd084c..abd7466 100644
--- a/src/commands/roll.rs
+++ b/src/commands/roll.rs
@@ -1,11 +1,11 @@
-use std::result::Result as StdResult;
-
 use lazy_static::lazy_static;
 use log::{
     debug,
     error,
 };
+use pest::iterators::Pair;
 use rand::prelude::*;
+use std::result::Result as StdResult;
 use thiserror::Error;
 
 use crate::{
@@ -32,10 +32,7 @@ pub(crate) enum CalcError {
 impl Calc {
     fn eval<S: AsRef<str>>(s: S) -> StdResult<f64, CalcError> {
         use pest::{
-            iterators::{
-                Pair,
-                Pairs,
-            },
+            iterators::Pairs,
             pratt_parser::PrattParser,
             Parser,
         };
@@ -46,16 +43,15 @@ impl Calc {
             static ref CLIMBER: PrattParser<Rule> = {
                 use pest::pratt_parser::{
                     Assoc::*,
-                    Op as Operator,
+                    Op,
                 };
 
                 PrattParser::new()
-                    .op(Operator::infix(add, Left)
-                        | Operator::infix(sub, Left)
-                        | Operator::infix(modulo, Left))
-                    .op(Operator::infix(mul, Left) | Operator::infix(div, Left))
-                    .op(Operator::infix(dice, Left))
-                    .op(Operator::infix(pow, Right))
+                    .op(Op::infix(add, Left) | Op::infix(sub, Left) | Op::infix(modulo, Left))
+                    .op(Op::infix(mul, Left) | Op::infix(div, Left))
+                    .op(Op::infix(dice, Left))
+                    .op(Op::infix(pow, Right))
+                    .op(Op::postfix(EOI)) // discarded below
             };
         }
 
@@ -172,6 +168,7 @@ impl Calc {
 
                     Ok(result)
                 })
+                .map_postfix(|arg, _post| arg) // discard EOI
                 .parse(p)
         }
 
@@ -202,7 +199,8 @@ mod test {
     }
 }
 
-#[poise::command(slash_command, prefix_command, guild_only, aliases("calc", "calculate"))]
+/// Roll some number of dice or perform a calculation.
+#[poise::command(prefix_command, guild_only, aliases("calc", "calculate"))]
 pub async fn roll(ctx: PoiseContext<'_>, #[rest] rest: String) -> anyhow::Result<()> {
     match Calc::eval(&rest) {
         Ok(result) => {
-- 
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