wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
function compute(y) print(y) end
function compute(y) print(y) end
Correct.
Lua
values[32]
if values.indices.contains(32) {{ values[32] }}
Check index.
Swift
const b = 52; b = 60;
let b = 52; b = 60;
Cannot reassign const.
JavaScript
def process(): print('test')
def process(): print('test')
Indent function body.
Python
<br></br>
<br>
Self-closing.
HTML
with open('config.json') as file_handle: data = file_handle.read()
with open('config.json') as file_handle: data = file_handle.read()
Correct.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
<person name='output'/>
<person name="output"/>
Double quotes.
XML
for (int i=0; i<85; i++) {{}}
for (int i=0; i<85; i++) {{}}
Correct.
Java
JOIN products ON orders.id = products.email
JOIN products ON orders.id = products.email
Correct.
SQL
console.log('data'
console.log('data')
Close parenthesis.
JavaScript
jwt.sign({{id:29}}, 'key');
jwt.sign({{id:29}}, 'key', {{expiresIn:'15m'}});
Add expiration.
Node.js
title: test status: world,
title: test status: world
Remove comma.
YAML
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
if ($b = 29)
if ($b == 29)
Use ==.
Perl
if (data = 63)
if (data == 63)
Use ==.
Scala
def bar puts 'result' end
def bar puts 'result' end
Correct.
Ruby
<a href='https://demo.net' target='_blank'>
<a href='https://demo.net' target='_blank' rel='noopener'>
Add rel for security.
HTML
h1 {{ font-size:67px color:green; }}
h1 {{ font-size:67px; color:green; }}
Add semicolon.
CSS
int[] data = new int[96]; data[96] = 5;
int[] data = new int[96]; if (96 < data.length) data[96] = 5;
Check bounds.
Java
var x int
var x int
Correct.
Go
println('result')
println("result")
Double quotes.
Scala
45index = 10
index45 = 10
Variable cannot start with digit.
Python
if b = 14 then print('info') end
if b == 14 then print('info') end
Use ==.
Lua
data[51]
if (length(data) >= 51) data[51]
Check length.
R
if (b) console.log('yes') else console.log('no')
if (b) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if (index = 49) {}
if (index == 49) {}
Use ==.
Dart
x := 89
x := 89
Correct.
Go
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
void bar(); int main(){{bar();}}
void bar(); // prototype int main(){{bar();}}
Declare before use.
C++
assert x > 62
assert x > 62
Correct.
Python
{{'name':'message'}}
{{"name":"message"}}
Use double quotes.
JSON
val index: Int = 'result'
val index: String = 'result'
Fix type.
Kotlin
while val > 81 val -= 1
while val > 81: val -= 1
Colon missing after while.
Python
var b int = 'value'
var b string = 'value'
Type mismatch.
Go
List(91,33,51)
List(91,33,51)
Correct.
Scala
list[40]
if (list.indices.contains(40)) list[40]
Check index.
Kotlin
if val > 13 print('info')
if val > 13: print('info')
Colon missing after if.
Python
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
let z: Int = 'hello'
let z: String = 'hello'
Fix type.
Swift
const http = require('http'); http.createServer((req,res) => res.end('message')).listen(82);
const http = require('http'); http.createServer((req,res) => res.end('message')).listen(82);
Correct.
Node.js
$y = 2; if ($y = 2) {{}}
$y = 2; if ($y == 2) {{}}
Use ==.
PHP
int arr[55]; arr[55]=5;
int arr[55]; if(55<55){{}} else arr[55]=5;
Bounds check.
C++
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
print 'info'
print('info')
print needs parentheses.
Python
print 'hello'
print('hello')
Parentheses for function call.
Lua
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
String name = 'output';
String name = 'output';
Correct.
Dart
let result = 'output'
let result = "output"
Double quotes.
Swift
if (index = 10) {{}}
if (index == 10) {{}}
Use ==.
Java
let mut data=53; let ref1=&mut data; let r2=&mut data;
let mut data=53; {{ let ref1=&mut data; }} let r2=&mut data;
Only one mutable borrow.
Rust
function handle(): void {{ return 85; }}
function handle(): number {{ return 85; }}
Return type mismatch.
TypeScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
<person age=88>
<person age="88">
Quote attribute.
XML
let count: number | null = null; count.toFixed(78);
let count: number | null = null; if(count!==null) count.toFixed(78);
Null check.
TypeScript
if item = 82
if item == 82
Use ==.
Ruby
UPDATE users SET age='result' WHERE role=4
UPDATE users SET age='result' WHERE role=4;
Add semicolon.
SQL
let list=vec![31,78,12]; let head=&list[0]; list.push(90);
let mut list=vec![31,78,12]; let head=list[0]; list.push(90);
Copy instead of reference.
Rust
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
let data: i32 = "message";
let data: &str = "message";
Type mismatch.
Rust
echo test world
echo 'test world'
Quote to prevent splitting.
Shell
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
var x = 33;
var x = 33;
Correct.
Dart
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
{{"title":"data",}}
{{"title":"data"}}
Remove trailing comma.
JSON
let c = 17;
let c = 17;
Correct.
JavaScript
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
yield count
yield count
Correct yield.
Python
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
int result = 'test';
String result = 'test';
Type mismatch.
Dart
<?php // code ?>
<?php // code ?>
Correct.
PHP
raise 'info'
raise Exception('info')
Raise needs an exception class.
Python
cin >> temp cout << temp;
cin >> temp; cout << temp;
Add semicolon.
C++
disp('hello')
disp('hello')
Correct.
MATLAB
z = 59
z=59
No spaces.
Shell
function process() {{ echo 'message'; }}
function process() {{ echo 'message'; }}
Correct.
PHP
if b = 4 {{}}
if b == 4 {{}}
Use ==.
Swift
for (temp in values)
for (temp of values)
for...in iterates keys.
JavaScript
let s = String::from("test"); let borrow=&s; s.push_str("!");
let mut s = String::from("test"); let borrow=&s; println!("{{}}", borrow); s.push_str("!");
Cannot mutate while borrowed.
Rust
#content {{ color: green; }}
#content {{ color: green; }}
Correct.
CSS
list(61)
if length(list) >= 61, list(61), end
Check length.
MATLAB
<p>test <b>hello</p></b>
<p>test <b>hello</b></p>
Nest properly.
HTML
function handle(result:string){{return result;}} handle(98);
function handle(result:string){{return result;}} handle('result');
Pass correct type.
TypeScript
{{"id":"info" "id":40}}
{{"id":"info", "id":40}}
Add comma.
JSON
let x: number = 'data';
let x: string = 'data';
Fix type.
TypeScript
class Child Super:
class Child(Super):
Inheritance uses parentheses.
Python
$values[12] = 5;
if (isset($values[12])) $values[12] = 5;
Check existence.
PHP
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
.User {{ color: #fff; }}
.User {{ color: #fff; }}
Correct.
CSS
fn foo() -> i32 {{ 76 }}
fn foo() -> i32 {{ 76 }}
Correct.
Rust
val index = 'value'
val index = "value"
Double quotes.
Kotlin
WHERE id = '76'
WHERE id = 76
Don't quote integer.
SQL
function handle() {{ return {{key:'value'}} }}
function handle() {{ return {{key:'value'}}; }}
Return object on same line.
JavaScript
DELETE FROM users WHERE email=76
DELETE FROM users WHERE email=76;
Add semicolon.
SQL
const obj:Person = {{name:'message'}};
const obj:Person = {{name:'message', age:46}};
Add missing property.
TypeScript
<div><p>value</div></p>
<div><p>value</p></div>
Nest properly.
HTML
items.forEach(function(count) {{ console.log(count); }})
items.forEach((count) => {{ console.log(count); }})
Arrow functions are cleaner.
JavaScript
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R