IR Calculator without any calculator bugs

1/*
2This is an IR Remote Controlled Calculator.
3I have tried to get
4  rid of all the bugs that I have seen
5in other calculators made using an arduino.
6  This calculator
7can be used like a normal calculator, you can make 
8simultaneous
9  calculations with this, add points, etc.
10The LCD Display used here is a RG1602A,
11you
12  may refer to this article to understand how to use the display,
13https://create.arduino.cc/projecthub/najad/interfacing-lcd1602-with-arduino-764ec4
14All
15  you need to do is connect the wires in the corresponding
16pins written down below
17  and edit the IR Codes:
18|------#------Arduino Pins------LCD RG1602A--------------------|
19|-----
20  1 ----     GND     ----- VSS,V0 (With 2K ohm),RW,K -----|
21|----- 2 ----     5V
22      ----- VDD, A (With 220 ohm)     -----|
23|----- 3 ----     12      -----
24  RS                        -----|
25|----- 4 ----     11      ----- E                         -----|
26|-----
27  5 ----     5       ----- D4                        -----|
28|----- 6 ----     4
29       ----- D5      	          -----|
30|----- 7 ----     3       ----- D6                        -----|
31|-----
32  8 ----     2       ----- D7                        -----|     
33|--------------------------------------------------------------|
34|------#------Arduino
35  Pins------IR Transmitter-----------------|
36|----- 1 ----     10      ----- Out
37                       -----|
38|----- 2 ----     GND     ----- GND                       -----|
39|-----
40  3 ----     5V      ----- Power                     -----|
41|--------------------------------------------------------------|
42Check
43  it out on Github: https://github.com/Jaagrav/IRcalculator/
44*/
45
46#include
47  <IRremote.h>
48#include <LiquidCrystal.h>
49#include <math.h>
50
51// Digital
52  Pin Connections to your LCD
53const int 
54  rs = 12, 
55  en = 11, 
56  d4
57  = 5, 
58  d5 = 4, 
59  d6 = 3, 
60  d7 = 2;
61
62LiquidCrystal lcd(rs, en,
63  d4, d5, d6, d7);
64
65// Digital Pin Connection to your IR Receiver
66IRrecv
67  irrecv(10);
68decode_results results;
69
70String 
71  number1 = "0",
72
73  number2 = "0",
74  optr = "=",
75  sixteenString = "                ";
76
77void
78  setup() {
79  Serial.begin(9600);
80  
81  lcd.begin(16, 2);
82  irrecv.enableIRIn();
83}
84
85void
86  loop() {
87  if (irrecv.decode(&results)) {
88    unsigned int result = results.value;
89
90    String val = String(result);
91    acceptInput(val.toInt());
92    irrecv.resume();
93  
94  } 
95  lcd.setCursor(0,0);
96  lcd.print(optr + "  " + sixteenString.substring(number1.length()
97  + 3) + number1);
98  lcd.setCursor(0,1);
99  lcd.print(sixteenString.substring(number2.length())
100  + number2);
101}
102
103void calculate(String op) {
104  double no1 = number1.toDouble();
105
106  double no2 = number2.toDouble();
107  double calcVal = 0.0;
108  
109  if(optr
110  == "+")
111    calcVal = (no1 + no2);
112  else if(optr == "-")
113    calcVal
114  = (no1 - no2);
115  else if(optr == "x")
116    calcVal = (no1 * no2);
117  else
118  if(optr == "/")
119    calcVal = (no1 / no2);
120  
121  number1 = toString(calcVal);
122
123  number2 = "0";
124  optr = op;
125}
126
127String toString(double num) {
128
129  return String(num);
130}
131
132void function(String e) { 
133  if(number1 !=
134  "0" && number2 != "0") {
135    calculate(e);
136  }
137  else if(number1 ==
138  "0") {  
139    number1 = number2;
140    number2 = "0";
141  }
142  optr =
143  e;
144}
145
146void concatNumbers(String num) {
147  if(optr == "=")
148    number1
149  = "0";
150  if(num != "."){
151    if(number2.length() == 1 && number2 == "0")
152
153       number2 = num;
154     else
155       number2 += num;  
156  }
157  else
158  {
159    if(number2.charAt(number2.length()-1) != '.' && number2.indexOf('.') ==
160  -1)
161      number2 += num;
162  }
163}
164
165void backSpace() {
166  number2
167  = number2.substring(0, number2.length() - 1);
168    if(number2 == "")
169      number2
170  = "0";
171}
172
173/*
174In the below switch-case replace the numbers with the
175  IR codes
176from your remote. Make sure you write the code that gets printed
177in
178  your serial monitor from line 142.
179*/
180
181void acceptInput(int character)
182  {
183  Serial.println(character);
184  switch(character) {
185  	case 2222: 
186
187      concatNumbers("1");
188    break;
189    case -31092:
190      concatNumbers("2");
191
192    break;
193    case 18888:
194      concatNumbers("3");
195    break;
196    case
197  10000:
198      concatNumbers("4");
199    break;
200    case -22203:
201      concatNumbers("5");
202
203    break;
204    case 26666:
205      concatNumbers("6");
206    break;
207    case
208  6333:
209      concatNumbers("7");
210    break;
211    case -25537:
212      concatNumbers("8");
213
214    break;
215    case 22222:
216      concatNumbers("9");
217    break;
218    case
219  12222:
220      concatNumbers("0");
221    break;
222    case 28888:
223      concatNumbers(".");
224
225    break;
226    case 255:
227      number1 = "0";
228      number2 = "0";
229
230      optr = "=";
231    break;
232    case 32222:
233      function("+");
234
235    break;
236    case -28870:
237      function("-");
238    break;
239    case
240  24444:
241      function("/");
242    break;
243    case 8444:
244      function("x");
245
246    break;
247    case 45555:
248      if(optr != "=")
249        calculate("=");
250
251    break;
252    case 4333:
253      backSpace();
254    break;
255    default:
256  
257    Serial.println("Invalid Input");
258  }
259}