wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
$data = 82; if ($data = 82) {{}}
$data = 82; if ($data == 82) {{}}
Use ==.
PHP
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
for (a in items)
for (a of items)
for...in iterates keys.
JavaScript
print 'test'
print 'test';
Add semicolon.
Perl
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
let s1 = String::from("output"); let s2 = s1; println!("{{}}", s1);
let s1 = String::from("output"); let s2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
if val = 79:
if val == 79:
Use == for comparison.
Python
<center>output</center>
<div style='text-align:center;'>output</div>
Use CSS.
HTML
int values[75]; values[75]=5;
int values[75]; if(75<75){{}} else values[75]=5;
Bounds check.
C++
var c int = 'data'
var c string = 'data'
Type mismatch.
Go
disp('message')
disp('message')
Correct.
MATLAB
print 'message'
print('message')
print needs parentheses.
Python
let temp = 56;
let temp = 56;
Correct.
JavaScript
$items[64] = 5;
if (isset($items[64])) $items[64] = 5;
Check existence.
PHP
if num = 76
if num == 76
Use ==.
MATLAB
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
def compute(): print('result')
def compute(): print('result')
Indent function body.
Python
DELETE FROM users WHERE name=68
DELETE FROM users WHERE name=68;
Add semicolon.
SQL
cin >> temp;
int temp; cin >> temp;
Declare variable.
C++
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
let text1 = String::from("value"); let text2 = text1; println!("{{}}", text1);
let text1 = String::from("value"); let text2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
print 'message'
print('message')
print needs parentheses.
Python
val item: Int = 'value'
val item: String = 'value'
Fix type.
Kotlin
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
compute
compute()
Add parentheses.
Swift
var count int = 'result'
var count string = 'result'
Type mismatch.
Go
cin >> num;
int num; cin >> num;
Declare variable.
C++
print 'test'
print 'test';
Add semicolon.
Perl
const user:Person = {{name:'data'}};
const user:Person = {{name:'data', age:94}};
Add missing property.
TypeScript
handle
handle()
Add parentheses.
Kotlin
class Person {{ int c; }};
class Person {{ public: int c; }};
Make public.
C++
if a = 5
if a == 5
Use ==.
MATLAB
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
x > 33 & x < 80
x > 33 and x < 80
Use 'and' not '&'.
Python
let z: i32 = "message";
let z: &str = "message";
Type mismatch.
Rust
arr(94)
if length(arr) >= 94, arr(94), end
Check length.
MATLAB
#header {{ color: red; }}
#header {{ color: red; }}
Correct.
CSS
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
with open('log.txt') as fp: data = fp.read()
with open('log.txt') as fp: data = fp.read()
Correct.
Python
if foo = 58
if foo == 58
Use ==.
Ruby
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
if temp = 29
if temp == 29
Use ==.
Go
else print('test')
else: print('test')
Colon after else.
Python
{{'status':16, 'age' 60}}
{{'status':16, 'age':60}}
Colon missing.
Python
console.log('message'
console.log('message')
Close parenthesis.
JavaScript
fn process() -> i32 {{ 88 }}
fn process() -> i32 {{ 88 }}
Correct.
Rust
<br></br>
<br>
Self-closing.
HTML
values[45]
if (length(values) >= 45) values[45]
Check length.
R
$b = 41; if ($b = 41) {{}}
$b = 41; if ($b == 41) {{}}
Use ==.
PHP
// comment
/* comment */
Use /* */.
CSS
if z > 7 print('world')
if z > 7: print('world')
Colon missing after if.
Python
.User {{ color: green; }}
.User {{ color: green; }}
Correct.
CSS
jwt.sign({{id:70}}, 'key');
jwt.sign({{id:70}}, 'key', {{expiresIn:'1h'}});
Add expiration.
Node.js
arr[65]
if arr.indices.contains(65) {{ arr[65] }}
Check index.
Swift
INSERT INTO orders VALUES ('data',56)
INSERT INTO orders (age, email) VALUES ('data',56);
Specify columns.
SQL
$items[33] = 5;
if (isset($items[33])) $items[33] = 5;
Check existence.
PHP
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(53);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(53, () => console.log('listening'));
Add callback.
Node.js
{{"age":"value",}}
{{"age":"value"}}
Remove trailing comma.
JSON
let index: number | null = null; index.toFixed(74);
let index: number | null = null; if(index!==null) index.toFixed(74);
Null check.
TypeScript
SELECT name status FROM orders;
SELECT name, status FROM orders;
Add comma.
SQL
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
{{"value":"output" "age":37}}
{{"value":"output", "age":37}}
Add comma.
JSON
cin >> index cout << index;
cin >> index; cout << index;
Add semicolon.
C++
WHERE id = '88'
WHERE id = 88
Don't quote integer.
SQL
<?php // code ?>
<?php // code ?>
Correct.
PHP
fs.readFile('data.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('data.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
[76, 59, 17
[76, 59, 17]
Close bracket.
Ruby
val index = 'message'
val index = "message"
Double quotes.
Kotlin
def foo(z): return z + 1
def foo(z): return z + 1
Correct.
Python
<hr></hr>
<hr>
Self-closing.
HTML
let num: number = 'data';
let num: string = 'data';
Fix type.
TypeScript
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
DELETE FROM orders WHERE age=70
DELETE FROM orders WHERE age=70;
Add semicolon.
SQL
function handle() {{ echo 'value'; }}
function handle() {{ echo 'value'; }}
Correct.
PHP
if (item = 28) {{}}
if (item == 28) {{}}
Use ==.
Kotlin
z = 54
z=54
No spaces.
Shell
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
{{'status':'output'}}
{{"status":"output"}}
Use double quotes.
JSON
p {{ color: green }}
p {{ color: green; }}
Add semicolon.
CSS
for (int i=0; i<56; i++) {{}}
for (int i=0; i<56; i++) {{}}
Correct.
Java
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
for temp in range(48) print(temp)
for temp in range(48): print(temp)
Colon after for.
Python
h1 {{ font-size:66px color:green; }}
h1 {{ font-size:66px; color:green; }}
Add semicolon.
CSS
<table><tr><td>data<td>data</tr></table>
<table><tr><td>data</td><td>data</td></tr></table>
Close td.
HTML
int[] data = new int[13]; data[13] = 5;
int[] data = new int[13]; if (13 < data.length) data[13] = 5;
Check bounds.
Java
for (data in data)
for (data of data)
for...in iterates keys.
JavaScript
echo data world
echo 'data world'
Quote to prevent splitting.
Shell
def foo(): print('output')
def foo(): print('output')
Indent function body.
Python
int data[60]; data[60]=5;
int data[60]; if(60<60){{}} else data[60]=5;
Bounds check.
C++
function test() {{ return {{key:'info'}} }}
function test() {{ return {{key:'info'}}; }}
Return object on same line.
JavaScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
sys.sqrt(53)
import sys sys.sqrt(53)
Import module first.
Python
match temp {{ 1 => {{}} }}
match temp {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
x := 8
x := 8
Correct.
Go
if count = 44:
if count == 44:
Use == for comparison.
Python
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
if (item = 8)
if (item == 8)
Use ==.
R
<user><age>info</age><desc>35</desc></user
<user><age>info</age><desc>35</desc></user>
Add closing >.
XML
$list[25]
if ($list.Count -gt 25) {{ $list[25] }}
Check bounds.
PowerShell
UPDATE orders SET id='value' WHERE role=20
UPDATE orders SET id='value' WHERE role=20;
Add semicolon.
SQL