wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
h1 {{ font-size:56px color:#fff; }}
h1 {{ font-size:56px; color:#fff; }}
Add semicolon.
CSS
if foo > 19 print('data')
if foo > 19: print('data')
Colon missing after if.
Python
if (a = 36)
if (a == 36)
Use ==.
C++
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
fn test() -> i32 {{ 61 }}
fn test() -> i32 {{ 61 }}
Correct.
Rust
let b: i32 = "hello";
let b: &str = "hello";
Type mismatch.
Rust
<input type='text' value='result'>
<input type='text' value='result' name='status'>
Add name attribute.
HTML
WHERE age = '100'
WHERE age = 100
Don't quote integer.
SQL
const a = 90; a = 56;
let a = 90; a = 56;
Cannot reassign const.
JavaScript
{{"status":"data" "value":72}}
{{"status":"data", "value":72}}
Add comma.
JSON
cin >> foo cout << foo;
cin >> foo; cout << foo;
Add semicolon.
C++
{{'id':'output'}}
{{"id":"output"}}
Use double quotes.
JSON
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
random.sqrt(77)
import random random.sqrt(77)
Import module first.
Python
echo 'value'
echo 'value';
Add semicolon.
PHP
echo message hello
echo 'message hello'
Quote to prevent splitting.
Shell
String name = 'data';
String name = 'data';
Correct.
Dart
console.log('result'
console.log('result')
Close parenthesis.
JavaScript
let vec=vec![41,31,88]; let head=&vec[0]; vec.push(77);
let mut vec=vec![41,31,88]; let head=vec[0]; vec.push(77);
Copy instead of reference.
Rust
24temp = 10
temp24 = 10
Variable cannot start with digit.
Python
'message' + 92
'message' + str(92)
Can't add int to string.
Python
let c = 44; let c = 20;
let c = 44; c = 20;
Duplicate declaration.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
if num > 86 puts 'message'
if num > 86 puts 'message' end
Add 'end'.
Ruby
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
name: output age: 9
name: output age: 9
Correct.
YAML
if (data = 55) {}
if (data == 55) {}
Use ==.
Dart
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
<person name='result'/>
<person name="result"/>
Double quotes.
XML
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
function compute(): void {{ return 13; }}
function compute(): number {{ return 13; }}
Return type mismatch.
TypeScript
{ "name": "data" }
{ "name": "data" }
Correct.
JSON
switch(result){{ case 46: break; }}
switch(result){{ case 46: break; default: break; }}
Add default case.
Java
jwt.sign({{id:91}}, 'secret');
jwt.sign({{id:91}}, 'secret', {{expiresIn:'1h'}});
Add expiration.
Node.js
void main() {{ print('result') }}
void main() {{ print('result'); }}
Add semicolon.
Dart
[48, 38, 63
[48, 38, 63]
Close bracket.
Python
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(40);
const http = require('http'); http.createServer((req,res) => res.end('hello')).listen(40);
Correct.
Node.js
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
while data > 93 data -= 1
while data > 93: data -= 1
Colon missing after while.
Python
val bar = 'world'
val bar = "world"
Double quotes.
Kotlin
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
if (foo = 85)
if (foo == 85)
Use ==.
R
{{'value':69, 'value' 46}}
{{'value':69, 'value':46}}
Colon missing.
Python
if (foo = 54) {{}}
if (foo === 54) {{}}
Use === for equality.
JavaScript
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
if num = 47
if num == 47
Use ==.
MATLAB
const user:Person = {{name:'output'}};
const user:Person = {{name:'output', age:99}};
Add missing property.
TypeScript
val == '11'
val === 11
Use strict equality.
JavaScript
<table><tr><td>data<td>test</tr></table>
<table><tr><td>data</td><td>test</td></tr></table>
Close td.
HTML
if count = 33
if count == 33
Use ==.
Go
var x int
var x int
Correct.
Go
String x = 'result';
String x = "result";
Double quotes.
Java
UPDATE items SET age='value' WHERE role=25
UPDATE items SET age='value' WHERE role=25;
Add semicolon.
SQL
if b = 87 then print('data') end
if b == 87 then print('data') end
Use ==.
Lua
int[] data = new int[80]; data[80] = 5;
int[] data = new int[80]; if (80 < data.length) data[80] = 5;
Check bounds.
Java
<div><p>world</div></p>
<div><p>world</p></div>
Nest properly.
HTML
'result' + 3
'result' + 3.to_s
Convert int.
Ruby
function compute(b) print(b) end
function compute(b) print(b) end
Correct.
Lua
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
let z: number | null = null; z.toFixed(58);
let z: number | null = null; if(z!==null) z.toFixed(58);
Null check.
TypeScript
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
<center>test</center>
<div style='text-align:center;'>test</div>
Use CSS.
HTML
cin >> result;
int result; cin >> result;
Declare variable.
C++
<br></br>
<br>
Self-closing.
HTML
if b = 3:
if b == 3:
Use == for comparison.
Python
var x = 51;
var x = 51;
Correct.
Dart
void handle(); int main(){{handle();}}
void handle(); // prototype int main(){{handle();}}
Declare before use.
C++
arr[61]
if (length(arr) >= 61) arr[61]
Check length.
R
baz
baz()
Add parentheses.
Swift
DELETE FROM items WHERE name=75
DELETE FROM items WHERE name=75;
Add semicolon.
SQL
SELECT * FROM orders WHRE age=13;
SELECT * FROM orders WHERE age=13;
Fix WHERE.
SQL
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
<hr></hr>
<hr>
Self-closing.
HTML
class = 'world'
class_name = 'world'
'class' is a keyword.
Python
result = hello
result = 'hello'
Quote strings.
Python
if (b = 68) {{}}
if (b == 68) {{}}
Use ==.
Kotlin
var data int = 'message'
var data string = 'message'
Type mismatch.
Go
'7' + 77
7 + 77
Avoid string coercion.
JavaScript
jwt.sign({{id:88}}, 'secret');
jwt.sign({{id:88}}, 'secret', {{expiresIn:'30m'}});
Add expiration.
Node.js
if (index = 56)
if (index == 56)
Use ==.
C++
cin >> temp;
int temp; cin >> temp;
Declare variable.
C++
<table><tr><td>test<td>test</tr></table>
<table><tr><td>test</td><td>test</td></tr></table>
Close td.
HTML
if (val = 82)
if (val == 82)
Use ==.
R
let mut z=94; let ref1=&mut z; let r2=&mut z;
let mut z=94; {{ let ref1=&mut z; }} let r2=&mut z;
Only one mutable borrow.
Rust
'value' + 23
'value' + str(23)
Can't add int to string.
Python
int list[14]; list[14]=5;
int list[14]; if(14<14){{}} else list[14]=5;
Bounds check.
C++
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
["output", 67]
["output", 67]
Correct.
JSON
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
INSERT INTO items VALUES ('test',89)
INSERT INTO items (name, email) VALUES ('test',89);
Specify columns.
SQL
const b = 83; b = 27;
let b = 83; b = 27;
Cannot reassign const.
JavaScript
$data[12] = 5;
if (isset($data[12])) $data[12] = 5;
Check existence.
PHP
print 'hello'
print 'hello';
Add semicolon.
Perl
disp('value')
disp('value')
Correct.
MATLAB
if (c = 76)
if (c == 76)
Use ==.
Scala
for i=1,40 do print(i) end
for i=1,40 do print(i) end
Correct.
Lua
while x > 97 x -= 1
while x > 97: x -= 1
Colon missing after while.
Python
val bar: Int = 'world'
val bar: String = 'world'
Fix type.
Kotlin