wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<note><desc>value</desc><desc>31</desc></note
<note><desc>value</desc><desc>31</desc></note>
Add closing >.
XML
UPDATE orders SET name='data' WHERE email=13
UPDATE orders SET name='data' WHERE email=13;
Add semicolon.
SQL
class = 'message'
class_name = 'message'
'class' is a keyword.
Python
int z = 'value';
String z = 'value';
Type mismatch.
Dart
SELECT * FROM orders WHRE age=36;
SELECT * FROM orders WHERE age=36;
Fix WHERE.
SQL
if (z = 19) {{}}
if (z == 19) {{}}
Use ==.
Java
cin >> y cout << y;
cin >> y; cout << y;
Add semicolon.
C++
def process puts 'info' end
def process puts 'info' end
Correct.
Ruby
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
{{'title':'output'}}
{{"title":"output"}}
Use double quotes.
JSON
if count = 78 then print('value') end
if count == 78 then print('value') end
Use ==.
Lua
age: test age: hello,
age: test age: hello
Remove comma.
YAML
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
'message' + 14
'message' + str(14)
Can't add int to string.
Python
INSERT INTO orders VALUES ('world',16)
INSERT INTO orders (id, role) VALUES ('world',16);
Specify columns.
SQL
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
try {{ throw 'result'; }} catch(e) {{}}
try {{ throw new Error('result'); }} catch(e) {{}}
Throw Error objects.
JavaScript
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
let s = String::from("result"); let ref=&s; s.push_str("!");
let mut s = String::from("result"); let ref=&s; println!("{{}}", ref); s.push_str("!");
Cannot mutate while borrowed.
Rust
function test(): void {{ return 20; }}
function test(): number {{ return 20; }}
Return type mismatch.
TypeScript
print 'hello'
print('hello')
Parentheses for function call.
Lua
var x int
var x int
Correct.
Go
if ($b = 97) {{}}
if ($b -eq 97) {{}}
Use -eq.
PowerShell
object Person {{ def main(args: Array[String]) = println("value") }}
object Person {{ def main(args: Array[String]): Unit = println("value") }}
Add return type Unit.
Scala
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
<ul><li>world<li>hello</ul>
<ul><li>world</li><li>hello</li></ul>
Close li.
HTML
echo test test
echo 'test test'
Quote to prevent splitting.
Shell
if b = 52
if b == 52
Use ==.
MATLAB
let result = 23; result += 1;
let mut result = 23; result += 1;
Need mut to modify.
Rust
match temp {{ 1 => {{}} }}
match temp {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
class User def method end end
class User def method end end
Correct.
Ruby
y == '63'
y === 63
Use strict equality.
JavaScript
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }});
fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
let b = 59; let b = 67;
let b = 59; b = 67;
Duplicate declaration.
JavaScript
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
print('test')
print('test')
Correct.
R
{{"id":"data",}}
{{"id":"data"}}
Remove trailing comma.
JSON
let a = 'data'
let a = "data"
Double quotes.
Swift
{ "name": "hello" }
{ "name": "hello" }
Correct.
JSON
if (y = 44)
if (y == 44)
Use ==.
R
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
values[3]
if (length(values) >= 3) values[3]
Check length.
R
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
$bar = 26; if ($bar = 26) {{}}
$bar = 26; if ($bar == 26) {{}}
Use ==.
PHP
while index > 77 index -= 1
while index > 77: index -= 1
Colon missing after while.
Python
if [ $result = 11 ]; then
if [ "$result" = 11 ]; then
Quote variable.
Shell
for (foo in items)
for (foo of items)
for...in iterates keys.
JavaScript
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
b = data
b = 'data'
Quote strings.
Python
disp('value')
disp('value')
Correct.
MATLAB
{{"title":"hello" "age":12}}
{{"title":"hello", "age":12}}
Add comma.
JSON
// comment
/* comment */
Use /* */.
CSS
.Item {{ color: #333; }}
.Item {{ color: #333; }}
Correct.
CSS
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
def bar(): print('data')
def bar(): print('data')
Indent function body.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
String name = 'output';
String name = 'output';
Correct.
Dart
def render(foo): return foo + 1
def render(foo): return foo + 1
Correct.
Python
function baz(b:string){{return b;}} baz(86);
function baz(b:string){{return b;}} baz('info');
Pass correct type.
TypeScript
class Order {{ int data; }};
class Order {{ public: int data; }};
Make public.
C++
[86, 81, 60
[86, 81, 60]
Close bracket.
Ruby
println('value')
println("value")
Double quotes.
Scala
compute
compute()
Add parentheses.
Swift
const count;
const count = 67;
Initialize const.
JavaScript
if index = 15
if index == 15
Use ==.
Go
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
JOIN profiles ON users.id = profiles.status
JOIN profiles ON users.id = profiles.status
Correct.
SQL
my @arr = (44,98,40);
my @arr = (44,98,40);
Correct.
Perl
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
int arr[5]; arr[5]=5;
int arr[5]; if(5<5){{}} else arr[5]=5;
Bounds check.
C++
name: data age: 39
name: data age: 39
Correct.
YAML
const c = 44; c = 21;
let c = 44; c = 21;
Cannot reassign const.
JavaScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
function foo(x) print(x) end
function foo(x) print(x) end
Correct.
Lua
for count in range(82) print(count)
for count in range(82): print(count)
Colon after for.
Python
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(33);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(33, () => console.log('listening'));
Add callback.
Node.js
b = 93
b=93
No spaces.
Shell
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
let x: Int = 'output'
let x: String = 'output'
Fix type.
Swift
x := 29
x := 29
Correct.
Go
let vec=vec![5,67,12]; let primary=&vec[0]; vec.push(35);
let mut vec=vec![5,67,12]; let primary=vec[0]; vec.push(35);
Copy instead of reference.
Rust
random.sqrt(80)
import random random.sqrt(80)
Import module first.
Python
if foo = 40:
if foo == 40:
Use == for comparison.
Python
cin >> num;
int num; cin >> num;
Declare variable.
C++
$values[29] = 5;
if (isset($values[29])) $values[29] = 5;
Check existence.
PHP
[41, 4, 95
[41, 4, 95]
Close bracket.
Python
else print('world')
else: print('world')
Colon after else.
Python
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
<center>test</center>
<div style='text-align:center;'>test</div>
Use CSS.
HTML
DELETE FROM users WHERE name=100
DELETE FROM users WHERE name=100;
Add semicolon.
SQL
if (b = 59) {}
if (b == 59) {}
Use ==.
Dart
26b = 10
b26 = 10
Variable cannot start with digit.
Python
List(94,85,2)
List(94,85,2)
Correct.
Scala
32num = 10
num32 = 10
Variable cannot start with digit.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
var x int
var x int
Correct.
Go