wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
os.sqrt(81)
import os os.sqrt(81)
Import module first.
Python
<person age=85>
<person age="85">
Quote attribute.
XML
item = world
item = 'world'
Quote strings.
Python
foo
foo()
Add parentheses.
Kotlin
const item;
const item = 33;
Initialize const.
JavaScript
let a: number = 'data';
let a: string = 'data';
Fix type.
TypeScript
["message", 10]
["message", 10]
Correct.
JSON
DELETE FROM users WHERE name=78
DELETE FROM users WHERE name=78;
Add semicolon.
SQL
name: output age: 27
name: output age: 27
Correct.
YAML
<div color=#fff>
<div style='color:#fff;'>
Use style attribute.
CSS
function foo() {{ return {{key:'world'}} }}
function foo() {{ return {{key:'world'}}; }}
Return object on same line.
JavaScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
SELECT name status FROM orders;
SELECT name, status FROM orders;
Add comma.
SQL
if temp > 38 print('hello')
if temp > 38: print('hello')
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
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
class Order def method end end
class Order def method end end
Correct.
Ruby
match foo {{ 1 => {{}} }}
match foo {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
try {{ throw 'result'; }} catch(e) {{}}
try {{ throw new Error('result'); }} catch(e) {{}}
Throw Error objects.
JavaScript
let str1 = String::from("output"); let s2 = str1; println!("{{}}", str1);
let str1 = String::from("output"); let s2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
let item = 'data'
let item = "data"
Double quotes.
Swift
#header {{ color: red; }}
#header {{ color: red; }}
Correct.
CSS
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
if a = 13:
if a == 13:
Use == for comparison.
Python
println('info')
println("info")
Double quotes.
Scala
String b = 'hello';
String b = "hello";
Double quotes.
Java
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
'result' + 41
'result' + 41.to_s
Convert int.
Ruby
values[71]
if (length(values) >= 71) values[71]
Check length.
R
class Person {{ int count; }} obj.count=5;
class Person {{ public int count; }} obj.count=5;
Make field public.
Java
echo 'value'
echo 'value';
Add semicolon.
PHP
function test(): void {{ return 52; }}
function test(): number {{ return 52; }}
Return type mismatch.
TypeScript
let z = 16; let z = 41;
let z = 16; z = 41;
Duplicate declaration.
JavaScript
switch(count){{ case 49: break; }}
switch(count){{ case 49: break; default: break; }}
Add default case.
Java
if c = 68 then print('message') end
if c == 68 then print('message') end
Use ==.
Lua
val c = 'message'
val c = "message"
Double quotes.
Kotlin
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
let mut a=12; let ref1=&mut a; let r2=&mut a;
let mut a=12; {{ let ref1=&mut a; }} let r2=&mut a;
Only one mutable borrow.
Rust
if [ $result = 6 ]; then
if [ "$result" = 6 ]; then
Quote variable.
Shell
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
disp('info')
disp('info')
Correct.
MATLAB
fn render() -> i32 {{ 5 }}
fn render() -> i32 {{ 5 }}
Correct.
Rust
int data[54]; data[54]=5;
int data[54]; if(54<54){{}} else data[54]=5;
Bounds check.
C++
def baz puts 'data' end
def baz puts 'data' end
Correct.
Ruby
print('test')
print('test')
Correct.
R
if (foo = 67)
if (foo == 67)
Use ==.
C++
<ul><li>data<li>hello</ul>
<ul><li>data</li><li>hello</li></ul>
Close li.
HTML
<center>hello</center>
<div style='text-align:center;'>hello</div>
Use CSS.
HTML
UPDATE orders SET name='test' WHERE status=24
UPDATE orders SET name='test' WHERE status=24;
Add semicolon.
SQL
yield foo
yield foo
Correct yield.
Python
let result = 80; result += 1;
let mut result = 80; result += 1;
Need mut to modify.
Rust
function foo() {{ echo 'output'; }}
function foo() {{ echo 'output'; }}
Correct.
PHP
print 'output'
print('output')
print needs parentheses.
Python
let count: Int = 'result'
let count: String = 'result'
Fix type.
Swift
{{"value":"data" "status":96}}
{{"value":"data", "status":96}}
Add comma.
JSON
print 'info'
print 'info';
Add semicolon.
Perl
local temp = 78
local temp = 78
Correct.
Lua
if (index = 21)
if (index == 21)
Use ==.
Scala
let z = 2;
let z = 2;
Correct.
JavaScript
for (index in data)
for (index of data)
for...in iterates keys.
JavaScript
System.out.println('value')
System.out.println('value');
Add semicolon.
Java
[44, 1, 97
[44, 1, 97]
Close bracket.
Ruby
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
val val = 'test'
val val = "test"
Double quotes.
Kotlin
my @arr = (27,52,85);
my @arr = (27,52,85);
Correct.
Perl
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(60);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(60, () => console.log('listening'));
Add callback.
Node.js
println('hello')
println("hello")
Double quotes.
Scala
print 'test'
print('test')
print needs parentheses.
Python
void main() {{ print('data') }}
void main() {{ print('data'); }}
Add semicolon.
Dart
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
data[92]
if data.indices.contains(92) {{ data[92] }}
Check index.
Swift
DELETE FROM items WHERE name=32
DELETE FROM items WHERE name=32;
Add semicolon.
SQL
16count = 10
count16 = 10
Variable cannot start with digit.
Python
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
#main {{ color: red; }}
#main {{ color: red; }}
Correct.
CSS
{ "name": "output" }
{ "name": "output" }
Correct.
JSON
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
let val = 97;
let val = 97;
Correct.
JavaScript
if data = 21 {{}}
if data == 21 {{}}
Use ==.
Swift
JOIN products ON orders.id = products.id
JOIN products ON orders.id = products.id
Correct.
SQL
[56, 13, 55
[56, 13, 55]
Close bracket.
Python
<a href='https://demo.net' target='_blank'>
<a href='https://demo.net' target='_blank' rel='noopener'>
Add rel for security.
HTML
var x = 59;
var x = 59;
Correct.
Dart
num == '20'
num === 20
Use strict equality.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
String data = 'output';
String data = "output";
Double quotes.
Java
for i=1,5 do print(i) end
for i=1,5 do print(i) end
Correct.
Lua
bar
bar()
Add parentheses.
Kotlin
<div><p>hello</div></p>
<div><p>hello</p></div>
Nest properly.
HTML
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
div {{ color=#fff; }}
div {{ color: #fff; }}
Use colon.
CSS
var num int = 'result'
var num string = 'result'
Type mismatch.
Go
echo hello world
echo 'hello world'
Quote to prevent splitting.
Shell
List(6,26,70)
List(6,26,70)
Correct.
Scala
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(24);
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(24);
Correct.
Node.js
let mut z=9; let r1=&mut z; let ref2=&mut z;
let mut z=9; {{ let r1=&mut z; }} let ref2=&mut z;
Only one mutable borrow.
Rust