Implement modulo.

3 files changed, 22 insertions, 2 deletions

diff --git a/src/eval.rs b/src/eval.rs
index d3b5ddc..e07bec2 100644
--- a/src/eval.rs
+++ b/src/eval.rs
@@ -1,5 +1,6 @@
 use num::pow::Pow;
-use num::{BigInt, FromPrimitive, Signed, ToPrimitive};
+use num::{BigInt, FromPrimitive, Integer, Signed, ToPrimitive};
+use std::cmp::Ordering;
 use std::fmt::{Display, Formatter};
 
 pub enum Num {
@@ -83,6 +84,21 @@ impl Num {
         }
     }
 
+    pub fn modulo(self, other: Num) -> Num {
+        match (self, other) {
+            (Num::Int(i1), Num::Int(i2)) => int(i1.mod_floor(&i2)),
+            (n1, n2) => {
+                let n1 = n1.as_float();
+                let n2 = n2.as_float();
+                let r = n1 % n2;
+                if r < 0. {
+                    return float(r + n2);
+                }
+                float(r)
+            }
+        }
+    }
+
     pub fn add(self, other: Num) -> Num {
         match (self, other) {
             (Num::Int(i1), Num::Int(i2)) => int(i1 + i2),
diff --git a/src/lexer.rs b/src/lexer.rs
index 49d2d04..4130760 100644
--- a/src/lexer.rs
+++ b/src/lexer.rs
@@ -56,7 +56,7 @@ impl<'a> Iterator for Lexer<'a> {
                 self.buf = &self.buf[1..];
                 return Some("/");
             }
-            b'+' | b'-' | b'*' | b'^' | b'(' | b')' => {
+            b'+' | b'-' | b'*' | b'%' | b'^' | b'(' | b')' => {
                 let t = &self.buf[..1];
                 self.buf = &self.buf[1..];
                 return Some(t);
diff --git a/src/parser.rs b/src/parser.rs
index b391202..3728ebf 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -199,6 +199,10 @@ impl<'a> Parser<'a> {
             let e2 = seq(self.expt_expr())?;
             return self.mul_expr_fold(e1.int_div(e2));
         }
+        if self.symbol("%") {
+            let e2 = seq(self.expt_expr())?;
+            return self.mul_expr_fold(e1.modulo(e2));
+        }
         // Allow implicit multiplication
         if let Some(e2) = or(self.expt_expr_no_num())? {
             return self.mul_expr_fold(e1.mul(e2));