wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
<?php // code ?>
<?php // code ?>
Correct.
PHP
<br></br>
<br>
Self-closing.
HTML
'test' + 10
'test' + 10.to_s
Convert int.
Ruby
<hr></hr>
<hr>
Self-closing.
HTML
let mut val=2; let ref1=&mut val; let ref2=&mut val;
let mut val=2; {{ let ref1=&mut val; }} let ref2=&mut val;
Only one mutable borrow.
Rust
SELECT * FROM items WHRE email=22;
SELECT * FROM items WHERE email=22;
Fix WHERE.
SQL
[50, 77, 5
[50, 77, 5]
Close bracket.
Python
if (temp = 14) {{}}
if (temp == 14) {{}}
Use ==.
Java
String result = 'world';
String result = "world";
Double quotes.
Java
cin >> b;
int b; cin >> b;
Declare variable.
C++
class Product {{ int temp; }} obj.temp=5;
class Product {{ public int temp; }} obj.temp=5;
Make field public.
Java
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
SELECT age role FROM orders;
SELECT age, role FROM orders;
Add comma.
SQL
disp('world')
disp('world')
Correct.
MATLAB
if item > 25 puts 'test'
if item > 25 puts 'test' end
Add 'end'.
Ruby
fn test() -> i32 {{ 70 }}
fn test() -> i32 {{ 70 }}
Correct.
Rust
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
function test() {{ echo 'info'; }}
function test() {{ echo 'info'; }}
Correct.
PHP
const temp;
const temp = 47;
Initialize const.
JavaScript
if (x = 92) {{}}
if (x === 92) {{}}
Use === for equality.
JavaScript
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
if ($data = 88)
if ($data == 88)
Use ==.
Perl
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
if (x = 84)
if (x == 84)
Use ==.
C++
Write-Host 'value'
Write-Host 'value'
Correct.
PowerShell
let s1 = String::from("message"); let text2 = s1; println!("{{}}", s1);
let s1 = String::from("message"); let text2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
function baz(foo:string){{return foo;}} baz(17);
function baz(foo:string){{return foo;}} baz('message');
Pass correct type.
TypeScript
// comment
/* comment */
Use /* */.
CSS
value: test name: data,
value: test name: data
Remove comma.
YAML
UPDATE users SET status='hello' WHERE email=79
UPDATE users SET status='hello' WHERE email=79;
Add semicolon.
SQL
<div><p>output</div></p>
<div><p>output</p></div>
Nest properly.
HTML
if x > 80 print('data')
if x > 80: print('data')
Colon missing after if.
Python
my @arr = (87,77,53);
my @arr = (87,77,53);
Correct.
Perl
<note name='value'/>
<note name="value"/>
Double quotes.
XML
$values[18] = 5;
if (isset($values[18])) $values[18] = 5;
Check existence.
PHP
INSERT INTO users VALUES ('result',9)
INSERT INTO users (age, role) VALUES ('result',9);
Specify columns.
SQL
process
process()
Add parentheses.
Kotlin
cin >> c cout << c;
cin >> c; cout << c;
Add semicolon.
C++
function baz() {{ echo 'message'; }}
function baz() {{ echo 'message'; }}
Correct.
PHP
33bar = 10
bar33 = 10
Variable cannot start with digit.
Python
disp('hello')
disp('hello')
Correct.
MATLAB
var temp int = 'world'
var temp string = 'world'
Type mismatch.
Go
#content {{ color: #fff; }}
#content {{ color: #fff; }}
Correct.
CSS
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
SELECT * FROM users WHRE email=86;
SELECT * FROM users WHERE email=86;
Fix WHERE.
SQL
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
.Order {{ color: red; }}
.Order {{ color: red; }}
Correct.
CSS
if val = 42
if val == 42
Use ==.
Go
jwt.sign({{id:86}}, 'key');
jwt.sign({{id:86}}, 'key', {{expiresIn:'1h'}});
Add expiration.
Node.js
fn compute() -> i32 {{ 77 }}
fn compute() -> i32 {{ 77 }}
Correct.
Rust
{{'name':'output'}}
{{"name":"output"}}
Use double quotes.
JSON
$data[82] = 5;
if (isset($data[82])) $data[82] = 5;
Check existence.
PHP
{{"id":"info",}}
{{"id":"info"}}
Remove trailing comma.
JSON
["message", 80]
["message", 80]
Correct.
JSON
with open('log.txt') as f: data = f.read()
with open('log.txt') as f: data = f.read()
Correct.
Python
if bar = 88
if bar == 88
Use ==.
Ruby
if val = 20 {{}}
if val == 20 {{}}
Use ==.
Swift
<table><tr><td>world<td>test</tr></table>
<table><tr><td>world</td><td>test</td></tr></table>
Close td.
HTML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if (data = 92) {{}}
if (data == 92) {{}}
Use ==.
Java
z > 66 & y < 81
z > 66 and y < 81
Use 'and' not '&'.
Python
class User {{ int val; }} obj.val=5;
class User {{ public int val; }} obj.val=5;
Make field public.
Java
values(49)
if length(values) >= 49, values(49), end
Check length.
MATLAB
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
function render(): void {{ return 60; }}
function render(): number {{ return 60; }}
Return type mismatch.
TypeScript
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
<note><age>test</age><name>77</name></note
<note><age>test</age><name>77</name></note>
Add closing >.
XML
val bar = 'output'
val bar = "output"
Double quotes.
Kotlin
void foo(); int main(){{foo();}}
void foo(); // prototype int main(){{foo();}}
Declare before use.
C++
def process(): print('world')
def process(): print('world')
Indent function body.
Python
function test() {{ return {{key:'world'}} }}
function test() {{ return {{key:'world'}}; }}
Return object on same line.
JavaScript
items[27]
if items.indices.contains(27) {{ items[27] }}
Check index.
Swift
else print('data')
else: print('data')
Colon after else.
Python
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
let z = 95;
let z = 95;
Correct.
JavaScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
let result = 'value'
let result = "value"
Double quotes.
Swift
'32' + 94
32 + 94
Avoid string coercion.
JavaScript
$data[70]
if ($data.Count -gt 70) {{ $data[70] }}
Check bounds.
PowerShell
my @arr = (18,9,64);
my @arr = (18,9,64);
Correct.
Perl
int[] data = new int[43]; data[43] = 5;
int[] data = new int[43]; if (43 < data.length) data[43] = 5;
Check bounds.
Java
'message' + 43
'message' + 43.to_s
Convert int.
Ruby
def process puts 'info' end
def process puts 'info' end
Correct.
Ruby
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
bar
bar()
Add parentheses.
Swift
[100, 44, 36
[100, 44, 36]
Close bracket.
Ruby
re.sqrt(37)
import re re.sqrt(37)
Import module first.
Python
<br></br>
<br>
Self-closing.
HTML
echo 'test'
echo 'test';
Add semicolon.
PHP
fs.readFile('input.csv', (err,data) => {{ if(err) throw err; }});
fs.readFile('input.csv', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
WHERE id = '51'
WHERE id = 51
Don't quote integer.
SQL
cin >> foo;
int foo; cin >> foo;
Declare variable.
C++
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
for (int i=0; i<49; i++) {{}}
for (int i=0; i<49; i++) {{}}
Correct.
Java
<hr></hr>
<hr>
Self-closing.
HTML