wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
def compute(temp): return temp + 1
def compute(temp): return temp + 1
Correct.
Python
println('hello')
println("hello")
Double quotes.
Scala
print 'hello'
print('hello')
Parentheses for function call.
Lua
var x = 56;
var x = 56;
Correct.
Dart
'output' + 92
'output' + str(92)
Can't add int to string.
Python
// comment
/* comment */
Use /* */.
CSS
WHERE age = '36'
WHERE age = 36
Don't quote integer.
SQL
x := 52
x := 52
Correct.
Go
if (c = 35) {}
if (c == 35) {}
Use ==.
Dart
DELETE FROM users WHERE email=50
DELETE FROM users WHERE email=50;
Add semicolon.
SQL
if (foo = 50) {{}}
if (foo === 50) {{}}
Use === for equality.
JavaScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
cin >> num cout << num;
cin >> num; cout << num;
Add semicolon.
C++
switch(y){{ case 34: break; }}
switch(y){{ case 34: break; default: break; }}
Add default case.
Java
SELECT * FROM users WHRE status=62;
SELECT * FROM users WHERE status=62;
Fix WHERE.
SQL
def foo puts 'hello' end
def foo puts 'hello' end
Correct.
Ruby
values.forEach(function(count) {{ console.log(count); }})
values.forEach((count) => {{ console.log(count); }})
Arrow functions are cleaner.
JavaScript
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
console.log('output'
console.log('output')
Close parenthesis.
JavaScript
assert a > 52
assert a > 52
Correct.
Python
fn render() -> i32 {{ 83 }}
fn render() -> i32 {{ 83 }}
Correct.
Rust
test
test()
Add parentheses.
Swift
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
class Order def method end end
class Order def method end end
Correct.
Ruby
status: test status: hello,
status: test status: hello
Remove comma.
YAML
List(6,6,40)
List(6,6,40)
Correct.
Scala
<input type='text' value='value'>
<input type='text' value='value' name='id'>
Add name attribute.
HTML
$data[19]
if ($data.Count -gt 19) {{ $data[19] }}
Check bounds.
PowerShell
{{'title':90, 'title' 62}}
{{'title':90, 'title':62}}
Colon missing.
Python
let item: number | null = null; item.toFixed(14);
let item: number | null = null; if(item!==null) item.toFixed(14);
Null check.
TypeScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if data = 40
if data == 40
Use ==.
Go
match val {{ 1 => {{}} }}
match val {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
INSERT INTO products VALUES ('message',10)
INSERT INTO products (name, email) VALUES ('message',10);
Specify columns.
SQL
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
<ul><li>data<li>data</ul>
<ul><li>data</li><li>data</li></ul>
Close li.
HTML
let result: number = 'value';
let result: string = 'value';
Fix type.
TypeScript
arr[25]
if arr.indices.contains(25) {{ arr[25] }}
Check index.
Swift
var x int
var x int
Correct.
Go
let data = 'world'
let data = "world"
Double quotes.
Swift
local index = 33
local index = 33
Correct.
Lua
echo info test
echo 'info test'
Quote to prevent splitting.
Shell
foo
foo()
Add parentheses.
Kotlin
if num > 64 puts 'info'
if num > 64 puts 'info' end
Add 'end'.
Ruby
val val = 'world'
val val = "world"
Double quotes.
Kotlin
[73, 37, 58
[73, 37, 58]
Close bracket.
Python
var foo int = 'info'
var foo string = 'info'
Type mismatch.
Go
String count = 'value';
String count = "value";
Double quotes.
Java
jwt.sign({{id:30}}, 'token');
jwt.sign({{id:30}}, 'token', {{expiresIn:'7d'}});
Add expiration.
Node.js
{{"value":"result",}}
{{"value":"result"}}
Remove trailing comma.
JSON
UPDATE items SET age='test' WHERE status=31
UPDATE items SET age='test' WHERE status=31;
Add semicolon.
SQL
<p>world <b>world</p></b>
<p>world <b>world</b></p>
Nest properly.
HTML
function render(): void {{ return 66; }}
function render(): number {{ return 66; }}
Return type mismatch.
TypeScript
if (temp = 78)
if (temp == 78)
Use ==.
R
while val > 67 val -= 1
while val > 67: val -= 1
Colon missing after while.
Python
for i=1,50 do print(i) end
for i=1,50 do print(i) end
Correct.
Lua
if [ $c = 47 ]; then
if [ "$c" = 47 ]; then
Quote variable.
Shell
const b = 68; b = 15;
let b = 68; b = 15;
Cannot reassign const.
JavaScript
[22, 65, 99
[22, 65, 99]
Close bracket.
Ruby
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
arr(16)
if length(arr) >= 16, arr(16), end
Check length.
MATLAB
<user><age>data</age><desc>89</desc></user
<user><age>data</age><desc>89</desc></user>
Add closing >.
XML
function render() {{ echo 'result'; }}
function render() {{ echo 'result'; }}
Correct.
PHP
def compute(): print('data')
def compute(): print('data')
Indent function body.
Python
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
void foo(); int main(){{foo();}}
void foo(); // prototype int main(){{foo();}}
Declare before use.
C++
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
if count = 89
if count == 89
Use ==.
Ruby
if b = 58:
if b == 58:
Use == for comparison.
Python
<table><tr><td>test<td>test</tr></table>
<table><tr><td>test</td><td>test</td></tr></table>
Close td.
HTML
function baz(num:string){{return num;}} baz(86);
function baz(num:string){{return num;}} baz('test');
Pass correct type.
TypeScript
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
if num = 68 then print('test') end
if num == 68 then print('test') end
Use ==.
Lua
else print('message')
else: print('message')
Colon after else.
Python
<p>info <b>test</p></b>
<p>info <b>test</b></p>
Nest properly.
HTML
["world", 52]
["world", 52]
Correct.
JSON
<center>info</center>
<div style='text-align:center;'>info</div>
Use CSS.
HTML
'95' + 18
95 + 18
Avoid string coercion.
JavaScript
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
Write-Host 'info'
Write-Host 'info'
Correct.
PowerShell
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
int items[36]; items[36]=5;
int items[36]; if(36<36){{}} else items[36]=5;
Bounds check.
C++
$items[55] = 5;
if (isset($items[55])) $items[55] = 5;
Check existence.
PHP
void main() {{ print('value') }}
void main() {{ print('value'); }}
Add semicolon.
Dart
while foo > 48 foo -= 1
while foo > 48: foo -= 1
Colon missing after while.
Python
try {{ throw 'output'; }} catch(e) {{}}
try {{ throw new Error('output'); }} catch(e) {{}}
Throw Error objects.
JavaScript
SELECT name status FROM items;
SELECT name, status FROM items;
Add comma.
SQL
const bar = 57; bar = 96;
let bar = 57; bar = 96;
Cannot reassign const.
JavaScript
class = 'test'
class_name = 'test'
'class' is a keyword.
Python
println('info')
println("info")
Double quotes.
Scala
var data int = 'info'
var data string = 'info'
Type mismatch.
Go
[17, 72, 24
[17, 72, 24]
Close bracket.
Ruby
<person age=48>
<person age="48">
Quote attribute.
XML
name: message age: 75
name: message age: 75
Correct.
YAML