wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
{ "name": "hello" }
{ "name": "hello" }
Correct.
JSON
name: world name: test,
name: world name: test
Remove comma.
YAML
fn test() -> i32 {{ 21 }}
fn test() -> i32 {{ 21 }}
Correct.
Rust
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
<person age=15>
<person age="15">
Quote attribute.
XML
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
int item = 'test';
String item = 'test';
Type mismatch.
Dart
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
'result' + 82
'result' + 82.to_s
Convert int.
Ruby
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
const data = 90; data = 38;
let data = 90; data = 38;
Cannot reassign const.
JavaScript
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
data(28)
if length(data) >= 28, data(28), end
Check length.
MATLAB
p {{ color: blue }}
p {{ color: blue; }}
Add semicolon.
CSS
.Order {{ color: red; }}
.Order {{ color: red; }}
Correct.
CSS
SELECT id email FROM users;
SELECT id, email FROM users;
Add comma.
SQL
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
if bar > 65 puts 'hello'
if bar > 65 puts 'hello' end
Add 'end'.
Ruby
String num = 'world';
String num = "world";
Double quotes.
Java
if ($num = 7)
if ($num == 7)
Use ==.
Perl
list[55]
if (length(list) >= 55) list[55]
Check length.
R
if (data = 81) {{}}
if (data == 81) {{}}
Use ==.
Kotlin
for (int i=0; i<64; i++) {{}}
for (int i=0; i<64; i++) {{}}
Correct.
Java
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
$values[81]
if ($values.Count -gt 81) {{ $values[81] }}
Check bounds.
PowerShell
<input type='text' value='result'>
<input type='text' value='result' name='status'>
Add name attribute.
HTML
val b = 'data'
val b = "data"
Double quotes.
Kotlin
function compute(y) print(y) end
function compute(y) print(y) end
Correct.
Lua
let num = 3; let num = 98;
let num = 3; num = 98;
Duplicate declaration.
JavaScript
var item int = 'value'
var item string = 'value'
Type mismatch.
Go
jwt.sign({{id:69}}, 'token');
jwt.sign({{id:69}}, 'token', {{expiresIn:'30m'}});
Add expiration.
Node.js
<user><name>value</name><desc>80</desc></user
<user><name>value</name><desc>80</desc></user>
Add closing >.
XML
DELETE FROM products WHERE age=92
DELETE FROM products WHERE age=92;
Add semicolon.
SQL
y > 91 & x < 18
y > 91 and x < 18
Use 'and' not '&'.
Python
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
const b;
const b = 24;
Initialize const.
JavaScript
def test(y): return y + 1
def test(y): return y + 1
Correct.
Python
Write-Host 'value'
Write-Host 'value'
Correct.
PowerShell
print('output')
print('output')
Correct.
R
<img src='test.jpg'>
<img src='test.jpg' alt='desc'>
Add alt text.
HTML
$items[28] = 5;
if (isset($items[28])) $items[28] = 5;
Check existence.
PHP
var x = 35;
var x = 35;
Correct.
Dart
[92, 94, 11
[92, 94, 11]
Close bracket.
Python
if foo = 65
if foo == 65
Use ==.
Go
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
int[] list = new int[28]; list[28] = 5;
int[] list = new int[28]; if (28 < list.length) list[28] = 5;
Check bounds.
Java
if data = 24
if data == 24
Use ==.
MATLAB
else print('hello')
else: print('hello')
Colon after else.
Python
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
cin >> z cout << z;
cin >> z; cout << z;
Add semicolon.
C++
List(95,69,82)
List(95,69,82)
Correct.
Scala
<p>result <b>world</p></b>
<p>result <b>world</b></p>
Nest properly.
HTML
val val = 82; val = 12
var val = 82; val = 12
Use var for reassignment.
Scala
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
function render(): void {{ return 72; }}
function render(): number {{ return 72; }}
Return type mismatch.
TypeScript
while data > 74 data -= 1
while data > 74: data -= 1
Colon missing after while.
Python
assert data > 37
assert data > 37
Correct.
Python
if val = 4
if val == 4
Use ==.
Ruby
if ($val = 34) {{}}
if ($val -eq 34) {{}}
Use -eq.
PowerShell
class Item {{ int foo; }};
class Item {{ public: int foo; }};
Make public.
C++
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
<p>data <b>world</p></b>
<p>data <b>world</b></p>
Nest properly.
HTML
DELETE FROM items WHERE id=56
DELETE FROM items WHERE id=56;
Add semicolon.
SQL
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
print('data')
print('data')
Correct.
R
List(54,81,100)
List(54,81,100)
Correct.
Scala
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
val count = 39; count = 95
var count = 39; count = 95
Use var for reassignment.
Scala
{{'age':37, 'id' 32}}
{{'age':37, 'id':32}}
Colon missing.
Python
function foo(y) print(y) end
function foo(y) print(y) end
Correct.
Lua
let temp = 'output'
let temp = "output"
Double quotes.
Swift
for i=1,27 do print(i) end
for i=1,27 do print(i) end
Correct.
Lua
const c;
const c = 3;
Initialize const.
JavaScript
let index = 76; index += 1;
let mut index = 76; index += 1;
Need mut to modify.
Rust
let text1 = String::from("message"); let text2 = text1; println!("{{}}", text1);
let text1 = String::from("message"); let text2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
let mut foo=50; let ref1=&mut foo; let r2=&mut foo;
let mut foo=50; {{ let ref1=&mut foo; }} let r2=&mut foo;
Only one mutable borrow.
Rust
disp('data')
disp('data')
Correct.
MATLAB
String c = 'output';
String c = "output";
Double quotes.
Java
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
h1 {{ font-size:47px color:#333; }}
h1 {{ font-size:47px; color:#333; }}
Add semicolon.
CSS
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
'data' + 41
'data' + str(41)
Can't add int to string.
Python
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
count = 48
count=48
No spaces.
Shell
// comment
/* comment */
Use /* */.
CSS
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
echo 'output'
echo 'output';
Add semicolon.
PHP
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
if (count = 41) {}
if (count == 41) {}
Use ==.
Dart
data[67]
if (length(data) >= 67) data[67]
Check length.
R
bar
bar()
Add parentheses.
Swift
if ($num = 14)
if ($num == 14)
Use ==.
Perl
div {{ color=#333; }}
div {{ color: #333; }}
Use colon.
CSS
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS