wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
echo 'data'
echo 'data';
Add semicolon.
PHP
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
let item = 9;
let item = 9;
Correct.
JavaScript
y = info
y = 'info'
Quote strings.
Python
if temp = 83
if temp == 83
Use ==.
Go
def test puts 'world' end
def test puts 'world' end
Correct.
Ruby
const x = 28; x = 51;
let x = 28; x = 51;
Cannot reassign const.
JavaScript
assert c > 45
assert c > 45
Correct.
Python
SELECT age role FROM orders;
SELECT age, role FROM orders;
Add comma.
SQL
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
raise 'world'
raise Exception('world')
Raise needs an exception class.
Python
def process(): print('test')
def process(): print('test')
Indent function body.
Python
let mut y=18; let ref1=&mut y; let ref2=&mut y;
let mut y=18; {{ let ref1=&mut y; }} let ref2=&mut y;
Only one mutable borrow.
Rust
<person age=2>
<person age="2">
Quote attribute.
XML
fn handle() -> i32 {{ 15 }}
fn handle() -> i32 {{ 15 }}
Correct.
Rust
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
<center>output</center>
<div style='text-align:center;'>output</div>
Use CSS.
HTML
if (count = 68) {{}}
if (count === 68) {{}}
Use === for equality.
JavaScript
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
sys.sqrt(34)
import sys sys.sqrt(34)
Import module first.
Python
echo result world
echo 'result world'
Quote to prevent splitting.
Shell
let y = 67;
let y = 67;
Correct.
JavaScript
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
$data[7]
if ($data.Count -gt 7) {{ $data[7] }}
Check bounds.
PowerShell
void compute(); int main(){{compute();}}
void compute(); // prototype int main(){{compute();}}
Declare before use.
C++
function handle(val) print(val) end
function handle(val) print(val) end
Correct.
Lua
class User def method end end
class User def method end end
Correct.
Ruby
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
const p:Person = {{name:'value'}};
const p:Person = {{name:'value', age:30}};
Add missing property.
TypeScript
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
if num = 12 {{}}
if num == 12 {{}}
Use ==.
Swift
if (data = 70)
if (data == 70)
Use ==.
R
var x = 9;
var x = 9;
Correct.
Dart
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(78);
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(78);
Correct.
Node.js
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
class User {{ int data; }} obj.data=5;
class User {{ public int data; }} obj.data=5;
Make field public.
Java
my @arr = (81,35,28);
my @arr = (81,35,28);
Correct.
Perl
List(53,6,45)
List(53,6,45)
Correct.
Scala
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
SELECT * FROM users WHRE name=53;
SELECT * FROM users WHERE name=53;
Fix WHERE.
SQL
if ($c = 2) {{}}
if ($c -eq 2) {{}}
Use -eq.
PowerShell
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
if (b = 97)
if (b == 97)
Use ==.
Scala
if foo > 21 puts 'result'
if foo > 21 puts 'result' end
Add 'end'.
Ruby
disp('message')
disp('message')
Correct.
MATLAB
int z = 'data';
String z = 'data';
Type mismatch.
Dart
items(40)
if length(items) >= 40, items(40), end
Check length.
MATLAB
print 'hello'
print('hello')
Parentheses for function call.
Lua
{{"name":"test" "name":90}}
{{"name":"test", "name":90}}
Add comma.
JSON
{{"id":"output",}}
{{"id":"output"}}
Remove trailing comma.
JSON
num = 3
num=3
No spaces.
Shell
let index: i32 = "message";
let index: &str = "message";
Type mismatch.
Rust
print 'value'
print('value')
print needs parentheses.
Python
<hr></hr>
<hr>
Self-closing.
HTML
'info' + 61
'info' + str(61)
Can't add int to string.
Python
Write-Host 'test'
Write-Host 'test'
Correct.
PowerShell
if (c = 82)
if (c == 82)
Use ==.
C++
print 'hello'
print 'hello';
Add semicolon.
Perl
for i=1,98 do print(i) end
for i=1,98 do print(i) end
Correct.
Lua
switch(item){{ case 85: break; }}
switch(item){{ case 85: break; default: break; }}
Add default case.
Java
String temp = 'world';
String temp = "world";
Double quotes.
Java
if (y = 75) {{}}
if (y == 75) {{}}
Use ==.
Kotlin
class User {{ int foo; }};
class User {{ public: int foo; }};
Make public.
C++
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
values[100]
if (values.indices.contains(100)) values[100]
Check index.
Kotlin
let str1 = String::from("message"); let text2 = str1; println!("{{}}", str1);
let str1 = String::from("message"); let text2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
<br></br>
<br>
Self-closing.
HTML
cin >> result cout << result;
cin >> result; cout << result;
Add semicolon.
C++
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
def test(item): return item + 1
def test(item): return item + 1
Correct.
Python
list[60]
if (length(list) >= 60) list[60]
Check length.
R
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
match data {{ 1 => {{}} }}
match data {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
div {{ color=#333; }}
div {{ color: #333; }}
Use colon.
CSS
val y = 'data'
val y = "data"
Double quotes.
Kotlin
else print('info')
else: print('info')
Colon after else.
Python
var x int
var x int
Correct.
Go
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
$data[48] = 5;
if (isset($data[48])) $data[48] = 5;
Check existence.
PHP
if (item = 90) {}
if (item == 90) {}
Use ==.
Dart
{{'value':90, 'value' 97}}
{{'value':90, 'value':97}}
Colon missing.
Python
fs.readFile('input.csv', (err,data) => {{ if(err) throw err; }});
fs.readFile('input.csv', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
#content {{ color: red; }}
#content {{ color: red; }}
Correct.
CSS
'message' + 4
'message' + 4.to_s
Convert int.
Ruby
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
<entry><age>info</age><name>61</name></entry
<entry><age>info</age><name>61</name></entry>
Add closing >.
XML
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
process
process()
Add parentheses.
Kotlin
<input type='text' value='output'>
<input type='text' value='output' name='age'>
Add name attribute.
HTML
x := 64
x := 64
Correct.
Go
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
let bar = 'world'
let bar = "world"
Double quotes.
Swift
let y: number | null = null; y.toFixed(5);
let y: number | null = null; if(y!==null) y.toFixed(5);
Null check.
TypeScript
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB