wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
83 values
language
stringclasses
23 values
echo 'message'
echo 'message';
Add semicolon.
PHP
for (temp in items)
for (temp of items)
for...in iterates keys.
JavaScript
$data[50] = 5;
if (isset($data[50])) $data[50] = 5;
Check existence.
PHP
{{"age":"message",}}
{{"age":"message"}}
Remove trailing comma.
JSON
let list=vec![53,43,46]; let head=&list[0]; list.push(68);
let mut list=vec![53,43,46]; let head=list[0]; list.push(68);
Copy instead of reference.
Rust
b = 19
b=19
No spaces.
Shell
values[74]
if (values.indices.contains(74)) values[74]
Check index.
Kotlin
if item = 22
if item == 22
Use ==.
Go
x := 44
x := 44
Correct.
Go
fs.readFile('log.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('log.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
items[70]
if items.indices.contains(70) {{ items[70] }}
Check index.
Swift
with open('config.json') as fh: data = fh.read()
with open('config.json') as fh: data = fh.read()
Correct.
Python
let y: number = 'hello';
let y: string = 'hello';
Fix type.
TypeScript
h1 {{ font-size:43px color:#333; }}
h1 {{ font-size:43px; color:#333; }}
Add semicolon.
CSS
[50, 97, 9
[50, 97, 9]
Close bracket.
Ruby
SELECT * FROM orders WHRE email=51;
SELECT * FROM orders WHERE email=51;
Fix WHERE.
SQL
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
def baz(): print('hello')
def baz(): print('hello')
Indent function body.
Python
[21, 42, 28
[21, 42, 28]
Close bracket.
Python
function test() {{ return {{key:'result'}} }}
function test() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
#footer {{ color: blue; }}
#footer {{ color: blue; }}
Correct.
CSS
cin >> num cout << num;
cin >> num; cout << num;
Add semicolon.
C++
x > 5 & z < 68
x > 5 and z < 68
Use 'and' not '&'.
Python
var foo int = 'value'
var foo string = 'value'
Type mismatch.
Go
function render(c:string){{return c;}} render(59);
function render(c:string){{return c;}} render('message');
Pass correct type.
TypeScript
'message' + 7
'message' + 7.to_s
Convert int.
Ruby
arr.forEach(function(val) {{ console.log(val); }})
arr.forEach((val) => {{ console.log(val); }})
Arrow functions are cleaner.
JavaScript
<p>value <b>test</p></b>
<p>value <b>test</b></p>
Nest properly.
HTML
id: message status: world,
id: message status: world
Remove comma.
YAML
let x: i32 = "output";
let x: &str = "output";
Type mismatch.
Rust
process
process()
Add parentheses.
Kotlin
if c > 33 print('info')
if c > 33: print('info')
Colon missing after if.
Python
a = output
a = 'output'
Quote strings.
Python
for (int i=0; i<79; i++) {{}}
for (int i=0; i<79; i++) {{}}
Correct.
Java
String y = 'output';
String y = "output";
Double quotes.
Java
my @arr = (62,78,98);
my @arr = (62,78,98);
Correct.
Perl
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
echo output data
echo 'output data'
Quote to prevent splitting.
Shell
<p>result <b>world</p></b>
<p>result <b>world</b></p>
Nest properly.
HTML
Write-Host 'test'
Write-Host 'test'
Correct.
PowerShell
if x = 45:
if x == 45:
Use == for comparison.
Python
int data[10]; data[10]=5;
int data[10]; if(10<10){{}} else data[10]=5;
Bounds check.
C++
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
index = value
index = 'value'
Quote strings.
Python
fmt.Println 'result'
fmt.Println('result')
Missing parentheses.
Go
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
WHERE age = '100'
WHERE age = 100
Don't quote integer.
SQL
<br></br>
<br>
Self-closing.
HTML
{{'title':'result'}}
{{"title":"result"}}
Use double quotes.
JSON
for (num in items)
for (num of items)
for...in iterates keys.
JavaScript
def foo puts 'hello' end
def foo puts 'hello' end
Correct.
Ruby
if [ $data = 89 ]; then
if [ "$data" = 89 ]; then
Quote variable.
Shell
echo 'info'
echo 'info';
Add semicolon.
PHP
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
else print('output')
else: print('output')
Colon after else.
Python
if (num = 15) {{}}
if (num == 15) {{}}
Use ==.
Java
disp('output')
disp('output')
Correct.
MATLAB
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
console.log('message'
console.log('message')
Close parenthesis.
JavaScript
val temp: Int = 'info'
val temp: String = 'info'
Fix type.
Kotlin
DELETE FROM products WHERE id=31
DELETE FROM products WHERE id=31;
Add semicolon.
SQL
x := 19
x := 19
Correct.
Go
if (b = 48) {{}}
if (b === 48) {{}}
Use === for equality.
JavaScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
my @arr = (48,80,44);
my @arr = (48,80,44);
Correct.
Perl
if (c = 7)
if (c == 7)
Use ==.
C++
<user name='info'/>
<user name="info"/>
Double quotes.
XML
if (item = 39) {{}}
if (item == 39) {{}}
Use ==.
Kotlin
x == '40'
x === 40
Use strict equality.
JavaScript
let item: Int = 'test'
let item: String = 'test'
Fix type.
Swift
function bar() {{ return {{key:'result'}} }}
function bar() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
<ul><li>test<li>data</ul>
<ul><li>test</li><li>data</li></ul>
Close li.
HTML
{{'id':58, 'id' 77}}
{{'id':58, 'id':77}}
Colon missing.
Python
const obj:Person = {{name:'value'}};
const obj:Person = {{name:'value', age:33}};
Add missing property.
TypeScript
SELECT * FROM products WHRE id=36;
SELECT * FROM products WHERE id=36;
Fix WHERE.
SQL
let list=vec![54,71,81]; let primary=&list[0]; list.push(31);
let mut list=vec![54,71,81]; let primary=list[0]; list.push(31);
Copy instead of reference.
Rust
int[] data = new int[71]; data[71] = 5;
int[] data = new int[71]; if (71 < data.length) data[71] = 5;
Check bounds.
Java
void handle(); int main(){{handle();}}
void handle(); // prototype int main(){{handle();}}
Declare before use.
C++
if ($y = 99) {{}}
if ($y -eq 99) {{}}
Use -eq.
PowerShell
String val = 'output';
String val = "output";
Double quotes.
Java
let b: number = 'output';
let b: string = 'output';
Fix type.
TypeScript
let b = 68;
let b = 68;
Correct.
JavaScript
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
json.sqrt(10)
import json json.sqrt(10)
Import module first.
Python
num = 10
num=10
No spaces.
Shell
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
if a = 18
if a == 18
Use ==.
Go
print 'hello'
print 'hello';
Add semicolon.
Perl
#footer {{ color: blue; }}
#footer {{ color: blue; }}
Correct.
CSS
jwt.sign({{id:41}}, 'secret');
jwt.sign({{id:41}}, 'secret', {{expiresIn:'7d'}});
Add expiration.
Node.js
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
[43, 11, 86
[43, 11, 86]
Close bracket.
Python
values[30]
if (length(values) >= 30) values[30]
Check length.
R
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(31);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(31, () => console.log('listening'));
Add callback.
Node.js
cin >> foo cout << foo;
cin >> foo; cout << foo;
Add semicolon.
C++
.Order {{ color: red; }}
.Order {{ color: red; }}
Correct.
CSS
var b int = 'data'
var b string = 'data'
Type mismatch.
Go
'data' + 21
'data' + 21.to_s
Convert int.
Ruby