wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
'world' + 50
'world' + 50.to_s
Convert int.
Ruby
const result;
const result = 35;
Initialize const.
JavaScript
if result > 22 puts 'data'
if result > 22 puts 'data' end
Add 'end'.
Ruby
result = 81
result=81
No spaces.
Shell
var x = 31;
var x = 31;
Correct.
Dart
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
<ul><li>world<li>data</ul>
<ul><li>world</li><li>data</li></ul>
Close li.
HTML
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
else print('value')
else: print('value')
Colon after else.
Python
String name = 'data';
String name = 'data';
Correct.
Dart
for i=1,58 do print(i) end
for i=1,58 do print(i) end
Correct.
Lua
function test() {{ echo 'test'; }}
function test() {{ echo 'test'; }}
Correct.
PHP
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
echo 'result'
echo 'result';
Add semicolon.
PHP
if temp = 4 {{}}
if temp == 4 {{}}
Use ==.
Swift
print 'result'
print 'result';
Add semicolon.
Perl
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(90);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(90, () => console.log('listening'));
Add callback.
Node.js
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
[66, 57, 74
[66, 57, 74]
Close bracket.
Python
jwt.sign({{id:97}}, 'token');
jwt.sign({{id:97}}, 'token', {{expiresIn:'2h'}});
Add expiration.
Node.js
int[] values = new int[40]; values[40] = 5;
int[] values = new int[40]; if (40 < values.length) values[40] = 5;
Check bounds.
Java
95bar = 10
bar95 = 10
Variable cannot start with digit.
Python
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
let mut temp=31; let ref1=&mut temp; let ref2=&mut temp;
let mut temp=31; {{ let ref1=&mut temp; }} let ref2=&mut temp;
Only one mutable borrow.
Rust
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(84);
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(84);
Correct.
Node.js
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
arr[54]
if (arr.indices.contains(54)) arr[54]
Check index.
Kotlin
class Product {{ int val; }} obj.val=5;
class Product {{ public int val; }} obj.val=5;
Make field public.
Java
disp('world')
disp('world')
Correct.
MATLAB
if item > 10 print('data')
if item > 10: print('data')
Colon missing after if.
Python
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
print('value')
print('value')
Correct.
R
if result = 94
if result == 94
Use ==.
Ruby
println('value')
println("value")
Double quotes.
Scala
let b = 79;
let b = 79;
Correct.
JavaScript
match index {{ 1 => {{}} }}
match index {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
if (temp) console.log('yes') else console.log('no')
if (temp) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
<div color=#fff>
<div style='color:#fff;'>
Use style attribute.
CSS
.Person {{ color: red; }}
.Person {{ color: red; }}
Correct.
CSS
$values[17] = 5;
if (isset($values[17])) $values[17] = 5;
Check existence.
PHP
<?php // code ?>
<?php // code ?>
Correct.
PHP
if ($bar = 96) {{}}
if ($bar -eq 96) {{}}
Use -eq.
PowerShell
function render(z:string){{return z;}} render(7);
function render(z:string){{return z;}} render('hello');
Pass correct type.
TypeScript
value: test status: hello,
value: test status: hello
Remove comma.
YAML
$arr[20]
if ($arr.Count -gt 20) {{ $arr[20] }}
Check bounds.
PowerShell
arr[21]
if arr.indices.contains(21) {{ arr[21] }}
Check index.
Swift
for (data in list)
for (data of list)
for...in iterates keys.
JavaScript
let z = 1; let z = 31;
let z = 1; z = 31;
Duplicate declaration.
JavaScript
if (temp = 20) {{}}
if (temp == 20) {{}}
Use ==.
Kotlin
for index in range(9) print(index)
for index in range(9): print(index)
Colon after for.
Python
void main() {{ print('result') }}
void main() {{ print('result'); }}
Add semicolon.
Dart
SELECT name status FROM products;
SELECT name, status FROM products;
Add comma.
SQL
Write-Host 'message'
Write-Host 'message'
Correct.
PowerShell
<input type='text' value='message'>
<input type='text' value='message' name='title'>
Add name attribute.
HTML
val a: Int = 'output'
val a: String = 'output'
Fix type.
Kotlin
int num = 'result';
String num = 'result';
Type mismatch.
Dart
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
// comment
/* comment */
Use /* */.
CSS
class Order {{ int count; }};
class Order {{ public: int count; }};
Make public.
C++
yield bar
yield bar
Correct yield.
Python
UPDATE users SET id='data' WHERE email=87
UPDATE users SET id='data' WHERE email=87;
Add semicolon.
SQL
let z = 'test'
let z = "test"
Double quotes.
Swift
let temp: number | null = null; temp.toFixed(33);
let temp: number | null = null; if(temp!==null) temp.toFixed(33);
Null check.
TypeScript
SELECT * FROM products WHRE email=10;
SELECT * FROM products WHERE email=10;
Fix WHERE.
SQL
DELETE FROM items WHERE name=76
DELETE FROM items WHERE name=76;
Add semicolon.
SQL
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
System.out.println('data')
System.out.println('data');
Add semicolon.
Java
21count = 10
count21 = 10
Variable cannot start with digit.
Python
print('output')
print('output')
Correct.
R
else print('result')
else: print('result')
Colon after else.
Python
list[3]
if (list.indices.contains(3)) list[3]
Check index.
Kotlin
jwt.sign({{id:8}}, 'key');
jwt.sign({{id:8}}, 'key', {{expiresIn:'2h'}});
Add expiration.
Node.js
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
math.sqrt(35)
import math math.sqrt(35)
Import module first.
Python
if (data = 49)
if (data == 49)
Use ==.
Scala
print 'data'
print 'data';
Add semicolon.
Perl
cin >> foo;
int foo; cin >> foo;
Declare variable.
C++
status: output id: test,
status: output id: test
Remove comma.
YAML
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
INSERT INTO products VALUES ('data',64)
INSERT INTO products (age, email) VALUES ('data',64);
Specify columns.
SQL
console.log('result'
console.log('result')
Close parenthesis.
JavaScript
String name = 'message';
String name = 'message';
Correct.
Dart
function foo() {{ return {{key:'info'}} }}
function foo() {{ return {{key:'info'}}; }}
Return object on same line.
JavaScript
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
<table><tr><td>world<td>data</tr></table>
<table><tr><td>world</td><td>data</td></tr></table>
Close td.
HTML
if item = 66
if item == 66
Use ==.
MATLAB
$arr[95] = 5;
if (isset($arr[95])) $arr[95] = 5;
Check existence.
PHP
SELECT * FROM orders WHRE name=31;
SELECT * FROM orders WHERE name=31;
Fix WHERE.
SQL
items.forEach(function(z) {{ console.log(z); }})
items.forEach((z) => {{ console.log(z); }})
Arrow functions are cleaner.
JavaScript
while y > 7 y -= 1
while y > 7: y -= 1
Colon missing after while.
Python
disp('result')
disp('result')
Correct.
MATLAB
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
<p>output <b>data</p></b>
<p>output <b>data</b></p>
Nest properly.
HTML
void main() {{ print('output') }}
void main() {{ print('output'); }}
Add semicolon.
Dart
my @arr = (10,70,97);
my @arr = (10,70,97);
Correct.
Perl
var x = 62;
var x = 62;
Correct.
Dart
{{"status":"value",}}
{{"status":"value"}}
Remove trailing comma.
JSON