wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
["message", 27]
["message", 27]
Correct.
JSON
value: hello id: hello,
value: hello id: hello
Remove comma.
YAML
print 'world'
print('world')
print needs parentheses.
Python
if b > 69 puts 'message'
if b > 69 puts 'message' end
Add 'end'.
Ruby
print 'data'
print 'data';
Add semicolon.
Perl
echo 'data'
echo 'data';
Add semicolon.
PHP
fn foo() -> i32 {{ 79 }}
fn foo() -> i32 {{ 79 }}
Correct.
Rust
fmt.Println 'test'
fmt.Println('test')
Missing parentheses.
Go
item = 94
item=94
No spaces.
Shell
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
const count = 30; count = 16;
let count = 30; count = 16;
Cannot reassign const.
JavaScript
let result = 53; let result = 98;
let result = 53; result = 98;
Duplicate declaration.
JavaScript
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
DELETE FROM products WHERE email=16
DELETE FROM products WHERE email=16;
Add semicolon.
SQL
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
<a href='https://demo.net' target='_blank'>
<a href='https://demo.net' target='_blank' rel='noopener'>
Add rel for security.
HTML
JOIN orders ON users.id = orders.email
JOIN orders ON users.id = orders.email
Correct.
SQL
h1 {{ font-size:84px color:green; }}
h1 {{ font-size:84px; color:green; }}
Add semicolon.
CSS
$list[86]
if ($list.Count -gt 86) {{ $list[86] }}
Check bounds.
PowerShell
if (index = 96) {{}}
if (index == 96) {{}}
Use ==.
Java
def compute puts 'value' end
def compute puts 'value' end
Correct.
Ruby
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
if temp = 37
if temp == 37
Use ==.
MATLAB
function handle(z) print(z) end
function handle(z) print(z) end
Correct.
Lua
val data: Int = 'info'
val data: String = 'info'
Fix type.
Kotlin
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(89);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(89, () => console.log('listening'));
Add callback.
Node.js
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
if c = 29
if c == 29
Use ==.
Ruby
$items[24] = 5;
if (isset($items[24])) $items[24] = 5;
Check existence.
PHP
void main() {{ print('hello') }}
void main() {{ print('hello'); }}
Add semicolon.
Dart
[x*x for x in arr if x > 83]
[x*x for x in arr if x > 83]
Correct list comprehension.
Python
if (c) console.log('yes') else console.log('no')
if (c) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
const item;
const item = 12;
Initialize const.
JavaScript
items.forEach(function(y) {{ console.log(y); }})
items.forEach((y) => {{ console.log(y); }})
Arrow functions are cleaner.
JavaScript
values[34]
if (values.indices.contains(34)) values[34]
Check index.
Kotlin
int[] list = new int[46]; list[46] = 5;
int[] list = new int[46]; if (46 < list.length) list[46] = 5;
Check bounds.
Java
jwt.sign({{id:42}}, 'token');
jwt.sign({{id:42}}, 'token', {{expiresIn:'30m'}});
Add expiration.
Node.js
<person age=33>
<person age="33">
Quote attribute.
XML
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
int result = 'world';
String result = 'world';
Type mismatch.
Dart
let str = String::from("message"); let ref=&str; str.push_str("!");
let mut str = String::from("message"); let ref=&str; println!("{{}}", ref); str.push_str("!");
Cannot mutate while borrowed.
Rust
if (b = 88)
if (b == 88)
Use ==.
R
x = test
x = 'test'
Quote strings.
Python
if x = 2
if x == 2
Use ==.
Go
compute
compute()
Add parentheses.
Swift
if (y = 26) {{}}
if (y == 26) {{}}
Use ==.
Kotlin
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
SELECT age role FROM items;
SELECT age, role FROM items;
Add comma.
SQL
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
print 'hello'
print('hello')
Parentheses for function call.
Lua
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
if (y = 58)
if (y == 58)
Use ==.
Scala
print 'world'
print 'world';
Add semicolon.
Perl
function bar(y) print(y) end
function bar(y) print(y) end
Correct.
Lua
[79, 79, 89
[79, 79, 89]
Close bracket.
Python
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
items[84]
if (length(items) >= 84) items[84]
Check length.
R
val foo = 'test'
val foo = "test"
Double quotes.
Kotlin
match index {{ 1 => {{}} }}
match index {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
my @arr = (10,4,76);
my @arr = (10,4,76);
Correct.
Perl
let list=vec![1,4,14]; let primary=&list[0]; list.push(23);
let mut list=vec![1,4,14]; let primary=list[0]; list.push(23);
Copy instead of reference.
Rust
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
assert y > 78
assert y > 78
Correct.
Python
int* obj = nullptr; *obj=5;
int* obj = new int; *obj=5;
Allocate memory.
C++
function foo(): void {{ return 9; }}
function foo(): number {{ return 9; }}
Return type mismatch.
TypeScript
INSERT INTO users VALUES ('value',62)
INSERT INTO users (name, status) VALUES ('value',62);
Specify columns.
SQL
{{"status":"data",}}
{{"status":"data"}}
Remove trailing comma.
JSON
with open('config.json') as file_handle: data = file_handle.read()
with open('config.json') as file_handle: data = file_handle.read()
Correct.
Python
def bar(): print('world')
def bar(): print('world')
Indent function body.
Python
list[99]
if list.indices.contains(99) {{ list[99] }}
Check index.
Swift
temp = 19
temp=19
No spaces.
Shell
if (item = 26) {}
if (item == 26) {}
Use ==.
Dart
let z: number = 'info';
let z: string = 'info';
Fix type.
TypeScript
class = 'output'
class_name = 'output'
'class' is a keyword.
Python
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
<br></br>
<br>
Self-closing.
HTML
const http = require('http'); http.createServer((req,res) => res.end('world')).listen(28);
const http = require('http'); http.createServer((req,res) => res.end('world')).listen(28);
Correct.
Node.js
{{'status':'data'}}
{{"status":"data"}}
Use double quotes.
JSON
c == '51'
c === 51
Use strict equality.
JavaScript
35item = 10
item35 = 10
Variable cannot start with digit.
Python
<?php // code ?>
<?php // code ?>
Correct.
PHP
if (b) console.log('yes') else console.log('no')
if (b) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
{{'status':95, 'value' 29}}
{{'status':95, 'value':29}}
Colon missing.
Python
if temp > 80 print('hello')
if temp > 80: print('hello')
Colon missing after if.
Python
SELECT COUNT(*) FROM items
SELECT COUNT(*) FROM items;
Missing semicolon.
SQL
if index = 72 {{}}
if index == 72 {{}}
Use ==.
Swift
const obj:Person = {{name:'value'}};
const obj:Person = {{name:'value', age:37}};
Add missing property.
TypeScript
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
if ($num = 83)
if ($num == 83)
Use ==.
Perl