From 08ff835658a5c6a113de269a39da74b6a0a8492e Mon Sep 17 00:00:00 2001
From: Pin Lin <moneycat711@gmail.com>
Date: Wed, 6 May 2020 07:07:12 +0800
Subject: [PATCH] =?UTF-8?q?=E5=AF=A6=E4=BD=9C=E6=8C=89=E4=B8=8B=20+/-=20?=
 =?UTF-8?q?=E8=A6=81=E6=80=8E=E9=BA=BC=E8=99=95=E7=90=86?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 AndroidCalculator/Calculator.swift | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/AndroidCalculator/Calculator.swift b/AndroidCalculator/Calculator.swift
index dd96340..f208ce9 100644
--- a/AndroidCalculator/Calculator.swift
+++ b/AndroidCalculator/Calculator.swift
@@ -62,6 +62,16 @@ class Calculator {
       }
       formula.append(text)
       
+    case "+/-":
+      if ["+", "-", "×", "÷"].firstIndex(of: formula.last!) != nil {
+        formula.append("0")
+      }
+      if formula.last!.firstIndex(of: "-") != nil {
+        formula.append(String(formula.popLast()!.split(separator: "-")[0]))
+      } else {
+        formula.append("-" + formula.popLast()!)
+      }
+      
     default:
       print(formula)
     }