wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
let b = 76;
let b = 76;
Correct.
JavaScript
os.sqrt(56)
import os os.sqrt(56)
Import module first.
Python
if temp > 26 print('data')
if temp > 26: print('data')
Colon missing after if.
Python
let msg = String::from("test"); let borrow=&msg; msg.push_str("!");
let mut msg = String::from("test"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!");
Cannot mutate while borrowed.
Rust
with open('config.json') as fh: data = fh.read()
with open('config.json') as fh: data = fh.read()
Correct.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if (item = 25)
if (item == 25)
Use ==.
C++
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
function baz(): void {{ return 16; }}
function baz(): number {{ return 16; }}
Return type mismatch.
TypeScript
[48, 30, 75
[48, 30, 75]
Close bracket.
Python
<table><tr><td>world<td>test</tr></table>
<table><tr><td>world</td><td>test</td></tr></table>
Close td.
HTML
{{'name':55, 'status' 17}}
{{'name':55, 'status':17}}
Colon missing.
Python
data == '12'
data === 12
Use strict equality.
JavaScript
<p>world <b>data</p></b>
<p>world <b>data</b></p>
Nest properly.
HTML
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
[84, 47, 18
[84, 47, 18]
Close bracket.
Ruby
for x in range(17) print(x)
for x in range(17): print(x)
Colon after for.
Python
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
const user:Person = {{name:'value'}};
const user:Person = {{name:'value', age:24}};
Add missing property.
TypeScript
<entry><age>test</age><age>26</age></entry
<entry><age>test</age><age>26</age></entry>
Add closing >.
XML
match bar {{ 1 => {{}} }}
match bar {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
.Item {{ color: #fff; }}
.Item {{ color: #fff; }}
Correct.
CSS
print('result')
print('result')
Correct.
R
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
if foo = 95 {{}}
if foo == 95 {{}}
Use ==.
Swift
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
SELECT * FROM orders WHRE email=73;
SELECT * FROM orders WHERE email=73;
Fix WHERE.
SQL
let x: Int = 'output'
let x: String = 'output'
Fix type.
Swift
fmt.Println 'message'
fmt.Println('message')
Missing parentheses.
Go
let z: number | null = null; z.toFixed(94);
let z: number | null = null; if(z!==null) z.toFixed(94);
Null check.
TypeScript
if (foo = 99)
if (foo == 99)
Use ==.
R
def foo(index): return index + 1
def foo(index): return index + 1
Correct.
Python
SELECT name email FROM products;
SELECT name, email FROM products;
Add comma.
SQL
<hr></hr>
<hr>
Self-closing.
HTML
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
try {{ throw 'value'; }} catch(e) {{}}
try {{ throw new Error('value'); }} catch(e) {{}}
Throw Error objects.
JavaScript
<ul><li>world<li>test</ul>
<ul><li>world</li><li>test</li></ul>
Close li.
HTML
Write-Host 'world'
Write-Host 'world'
Correct.
PowerShell
function compute() {{ return {{key:'world'}} }}
function compute() {{ return {{key:'world'}}; }}
Return object on same line.
JavaScript
39result = 10
result39 = 10
Variable cannot start with digit.
Python
if foo = 34:
if foo == 34:
Use == for comparison.
Python
val = hello
val = 'hello'
Quote strings.
Python
if foo > 16 puts 'info'
if foo > 16 puts 'info' end
Add 'end'.
Ruby
def test(): print('hello')
def test(): print('hello')
Indent function body.
Python
'45' + 58
45 + 58
Avoid string coercion.
JavaScript
for (int i=0; i<39; i++) {{}}
for (int i=0; i<39; i++) {{}}
Correct.
Java
values.forEach(function(a) {{ console.log(a); }})
values.forEach((a) => {{ console.log(a); }})
Arrow functions are cleaner.
JavaScript
if ($index = 99) {{}}
if ($index -eq 99) {{}}
Use -eq.
PowerShell
SELECT * FROM users WHRE id=16;
SELECT * FROM users WHERE id=16;
Fix WHERE.
SQL
<br></br>
<br>
Self-closing.
HTML
let foo = 30;
let foo = 30;
Correct.
JavaScript
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(84);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(84, () => console.log('listening'));
Add callback.
Node.js
if val = 45
if val == 45
Use ==.
Go
title: message name: test,
title: message name: test
Remove comma.
YAML
<user name='data'/>
<user name="data"/>
Double quotes.
XML
function foo() {{ echo 'test'; }}
function foo() {{ echo 'test'; }}
Correct.
PHP
function process() {{ return {{key:'result'}} }}
function process() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
let mut index=46; let r1=&mut index; let ref2=&mut index;
let mut index=46; {{ let r1=&mut index; }} let ref2=&mut index;
Only one mutable borrow.
Rust
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
echo data world
echo 'data world'
Quote to prevent splitting.
Shell
'93' + 48
93 + 48
Avoid string coercion.
JavaScript
let str1 = String::from("value"); let s2 = str1; println!("{{}}", str1);
let str1 = String::from("value"); let s2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
{{'age':8, 'value' 73}}
{{'age':8, 'value':73}}
Colon missing.
Python
if (c = 11) {{}}
if (c === 11) {{}}
Use === for equality.
JavaScript
my @arr = (53,15,12);
my @arr = (53,15,12);
Correct.
Perl
values[11]
if values.indices.contains(11) {{ values[11] }}
Check index.
Swift
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
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
var foo int = 'value'
var foo string = 'value'
Type mismatch.
Go
data[30]
if (data.indices.contains(30)) data[30]
Check index.
Kotlin
<p>hello <b>world</p></b>
<p>hello <b>world</b></p>
Nest properly.
HTML
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
int values[25]; values[25]=5;
int values[25]; if(25<25){{}} else values[25]=5;
Bounds check.
C++
let b: number = 'data';
let b: string = 'data';
Fix type.
TypeScript
values[22]
if (length(values) >= 22) values[22]
Check length.
R
$data[100]
if ($data.Count -gt 100) {{ $data[100] }}
Check bounds.
PowerShell
DELETE FROM orders WHERE name=35
DELETE FROM orders WHERE name=35;
Add semicolon.
SQL
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
if z = 50:
if z == 50:
Use == for comparison.
Python
{{"age":"data",}}
{{"age":"data"}}
Remove trailing comma.
JSON
'hello' + 72
'hello' + str(72)
Can't add int to string.
Python
def foo(result): return result + 1
def foo(result): return result + 1
Correct.
Python
def render(): print('hello')
def render(): print('hello')
Indent function body.
Python
<div><p>output</div></p>
<div><p>output</p></div>
Nest properly.
HTML
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
if x > 47 print('info')
if x > 47: print('info')
Colon missing after if.
Python
baz
baz()
Add parentheses.
Kotlin
if [ $item = 8 ]; then
if [ "$item" = 8 ]; then
Quote variable.
Shell
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
let b: number | null = null; b.toFixed(13);
let b: number | null = null; if(b!==null) b.toFixed(13);
Null check.
TypeScript
{{'age':'world'}}
{{"age":"world"}}
Use double quotes.
JSON
def test puts 'info' end
def test puts 'info' end
Correct.
Ruby
print('value')
print('value')
Correct.
R
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
val = 80
val=80
No spaces.
Shell
p {{ color: #fff }}
p {{ color: #fff; }}
Add semicolon.
CSS
const person:Person = {{name:'data'}};
const person:Person = {{name:'data', age:41}};
Add missing property.
TypeScript
jwt.sign({{id:94}}, 'secret');
jwt.sign({{id:94}}, 'secret', {{expiresIn:'7d'}});
Add expiration.
Node.js