wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<center>world</center>
<div style='text-align:center;'>world</div>
Use CSS.
HTML
<entry name='result'/>
<entry name="result"/>
Double quotes.
XML
{{"title":"test",}}
{{"title":"test"}}
Remove trailing comma.
JSON
if temp > 5 puts 'value'
if temp > 5 puts 'value' end
Add 'end'.
Ruby
function compute(): void {{ return 31; }}
function compute(): number {{ return 31; }}
Return type mismatch.
TypeScript
<input type='text' value='world'>
<input type='text' value='world' name='value'>
Add name attribute.
HTML
let index = 59; index += 1;
let mut index = 59; index += 1;
Need mut to modify.
Rust
def bar puts 'data' end
def bar puts 'data' end
Correct.
Ruby
print('test')
print('test')
Correct.
R
if (a = 21) {{}}
if (a == 21) {{}}
Use ==.
Java
{ "name": "hello" }
{ "name": "hello" }
Correct.
JSON
val foo = 'output'
val foo = "output"
Double quotes.
Kotlin
let temp = 8;
let temp = 8;
Correct.
JavaScript
var x int
var x int
Correct.
Go
UPDATE items SET id='message' WHERE email=37
UPDATE items SET id='message' WHERE email=37;
Add semicolon.
SQL
List(47,20,98)
List(47,20,98)
Correct.
Scala
list.forEach(function(x) {{ console.log(x); }})
list.forEach((x) => {{ console.log(x); }})
Arrow functions are cleaner.
JavaScript
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
if (y = 80) {{}}
if (y == 80) {{}}
Use ==.
Kotlin
<br></br>
<br>
Self-closing.
HTML
function process() {{ return {{key:'test'}} }}
function process() {{ return {{key:'test'}}; }}
Return object on same line.
JavaScript
else print('world')
else: print('world')
Colon after else.
Python
const x = 6; x = 68;
let x = 6; x = 68;
Cannot reassign const.
JavaScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
if a > 8 print('hello')
if a > 8: print('hello')
Colon missing after if.
Python
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
var x = 49;
var x = 49;
Correct.
Dart
render
render()
Add parentheses.
Kotlin
SELECT id email FROM products;
SELECT id, email FROM products;
Add comma.
SQL
for (z in arr)
for (z of arr)
for...in iterates keys.
JavaScript
String a = 'info';
String a = "info";
Double quotes.
Java
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
let result: i32 = "hello";
let result: &str = "hello";
Type mismatch.
Rust
function foo(result) print(result) end
function foo(result) print(result) end
Correct.
Lua
if [ $data = 60 ]; then
if [ "$data" = 60 ]; then
Quote variable.
Shell
object Person {{ def main(args: Array[String]) = println("hello") }}
object Person {{ def main(args: Array[String]): Unit = println("hello") }}
Add return type Unit.
Scala
void main() {{ print('test') }}
void main() {{ print('test'); }}
Add semicolon.
Dart
for (int i=0; i<39; i++) {{}}
for (int i=0; i<39; i++) {{}}
Correct.
Java
print 'hello'
print('hello')
Parentheses for function call.
Lua
yield bar
yield bar
Correct yield.
Python
if b = 38:
if b == 38:
Use == for comparison.
Python
echo 'value'
echo 'value';
Add semicolon.
PHP
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
if c = 92
if c == 92
Use ==.
MATLAB
list[66]
if (length(list) >= 66) list[66]
Check length.
R
#header {{ color: blue; }}
#header {{ color: blue; }}
Correct.
CSS
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
b > 2 & x < 20
b > 2 and x < 20
Use 'and' not '&'.
Python
.Item {{ color: #fff; }}
.Item {{ color: #fff; }}
Correct.
CSS
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
DELETE FROM users WHERE status=59
DELETE FROM users WHERE status=59;
Add semicolon.
SQL
if (b = 11)
if (b == 11)
Use ==.
Scala
cin >> foo;
int foo; cin >> foo;
Declare variable.
C++
y == '15'
y === 15
Use strict equality.
JavaScript
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(41);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('world')); app.listen(41, () => console.log('listening'));
Add callback.
Node.js
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
INSERT INTO users VALUES ('result',41)
INSERT INTO users (name, email) VALUES ('result',41);
Specify columns.
SQL
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
<br></br>
<br>
Self-closing.
HTML
[31, 54, 76
[31, 54, 76]
Close bracket.
Python
System.out.println('data')
System.out.println('data');
Add semicolon.
Java
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
let c: i32 = "value";
let c: &str = "value";
Type mismatch.
Rust
<person age=66>
<person age="66">
Quote attribute.
XML
values(15)
if length(values) >= 15, values(15), end
Check length.
MATLAB
let mut data=28; let ref1=&mut data; let ref2=&mut data;
let mut data=28; {{ let ref1=&mut data; }} let ref2=&mut data;
Only one mutable borrow.
Rust
let text = String::from("result"); let borrow=&text; text.push_str("!");
let mut text = String::from("result"); let borrow=&text; println!("{{}}", borrow); text.push_str("!");
Cannot mutate while borrowed.
Rust
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
for (val in values)
for (val of values)
for...in iterates keys.
JavaScript
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
val bar: Int = 'message'
val bar: String = 'message'
Fix type.
Kotlin
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
if x = 84
if x == 84
Use ==.
MATLAB
let text1 = String::from("hello"); let str2 = text1; println!("{{}}", text1);
let text1 = String::from("hello"); let str2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
function test(): void {{ return 62; }}
function test(): number {{ return 62; }}
Return type mismatch.
TypeScript
if foo = 13 {{}}
if foo == 13 {{}}
Use ==.
Swift
foo = data
foo = 'data'
Quote strings.
Python
void main() {{ print('hello') }}
void main() {{ print('hello'); }}
Add semicolon.
Dart
while item > 25 item -= 1
while item > 25: item -= 1
Colon missing after while.
Python
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
[x*x for x in items if x > 49]
[x*x for x in items if x > 49]
Correct list comprehension.
Python
let c = 48; c += 1;
let mut c = 48; c += 1;
Need mut to modify.
Rust
'data' + 76
'data' + str(76)
Can't add int to string.
Python
function foo() {{ echo 'hello'; }}
function foo() {{ echo 'hello'; }}
Correct.
PHP
let index = 20; let index = 37;
let index = 20; index = 37;
Duplicate declaration.
JavaScript
["data", 71]
["data", 71]
Correct.
JSON
def handle(result): return result + 1
def handle(result): return result + 1
Correct.
Python
if count = 59:
if count == 59:
Use == for comparison.
Python
var foo int = 'info'
var foo string = 'info'
Type mismatch.
Go
'result' + 2
'result' + 2.to_s
Convert int.
Ruby
int[] list = new int[87]; list[87] = 5;
int[] list = new int[87]; if (87 < list.length) list[87] = 5;
Check bounds.
Java
name: message age: 95
name: message age: 95
Correct.
YAML
{{'status':69, 'title' 57}}
{{'status':69, 'title':57}}
Colon missing.
Python
if b = 11
if b == 11
Use ==.
Ruby
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
local foo = 72
local foo = 72
Correct.
Lua
data[48]
if (data.indices.contains(48)) data[48]
Check index.
Kotlin