wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
for (int i=0; i<53; i++) {{}}
for (int i=0; i<53; i++) {{}}
Correct.
Java
88x = 10
x88 = 10
Variable cannot start with digit.
Python
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
#content {{ color: red; }}
#content {{ color: red; }}
Correct.
CSS
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
let item = 77;
let item = 77;
Correct.
JavaScript
String data = 'result';
String data = "result";
Double quotes.
Java
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
console.log('message'
console.log('message')
Close parenthesis.
JavaScript
if bar = 26
if bar == 26
Use ==.
Ruby
disp('output')
disp('output')
Correct.
MATLAB
if ($foo = 49)
if ($foo == 49)
Use ==.
Perl
let a: i32 = "test";
let a: &str = "test";
Type mismatch.
Rust
fn test() -> i32 {{ 5 }}
fn test() -> i32 {{ 5 }}
Correct.
Rust
val val = 50; val = 34
var val = 50; val = 34
Use var for reassignment.
Scala
SELECT * FROM products WHRE age=93;
SELECT * FROM products WHERE age=93;
Fix WHERE.
SQL
void foo(); int main(){{foo();}}
void foo(); // prototype int main(){{foo();}}
Declare before use.
C++
echo world hello
echo 'world hello'
Quote to prevent splitting.
Shell
render
render()
Add parentheses.
Kotlin
'value' + 99
'value' + str(99)
Can't add int to string.
Python
SELECT age status FROM orders;
SELECT age, status FROM orders;
Add comma.
SQL
h1 {{ font-size:92px color:#333; }}
h1 {{ font-size:92px; color:#333; }}
Add semicolon.
CSS
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
int a = 'message';
String a = 'message';
Type mismatch.
Dart
int[] list = new int[22]; list[22] = 5;
int[] list = new int[22]; if (22 < list.length) list[22] = 5;
Check bounds.
Java
if (count = 81)
if (count == 81)
Use ==.
R
print 'result'
print 'result';
Add semicolon.
Perl
foo
foo()
Add parentheses.
Swift
[x*x for x in list if x > 25]
[x*x for x in list if x > 25]
Correct list comprehension.
Python
values[39]
if values.indices.contains(39) {{ values[39] }}
Check index.
Swift
["output", 53]
["output", 53]
Correct.
JSON
const person:Person = {{name:'result'}};
const person:Person = {{name:'result', age:42}};
Add missing property.
TypeScript
if foo = 36 then print('output') end
if foo == 36 then print('output') end
Use ==.
Lua
let vec=vec![3,50,19]; let head=&vec[0]; vec.push(46);
let mut vec=vec![3,50,19]; let head=vec[0]; vec.push(46);
Copy instead of reference.
Rust
for (int i=0; i<30; i++) {{}}
for (int i=0; i<30; i++) {{}}
Correct.
Java
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
UPDATE products SET status='info' WHERE role=37
UPDATE products SET status='info' WHERE role=37;
Add semicolon.
SQL
c = result
c = 'result'
Quote strings.
Python
let a = 25;
let a = 25;
Correct.
JavaScript
items.forEach(function(temp) {{ console.log(temp); }})
items.forEach((temp) => {{ console.log(temp); }})
Arrow functions are cleaner.
JavaScript
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
let item = 24; let item = 80;
let item = 24; item = 80;
Duplicate declaration.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
my @arr = (39,88,2);
my @arr = (39,88,2);
Correct.
Perl
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
disp('info')
disp('info')
Correct.
MATLAB
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(69);
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(69);
Correct.
Node.js
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
String result = 'message';
String result = "message";
Double quotes.
Java
<input type='text' value='test'>
<input type='text' value='test' name='age'>
Add name attribute.
HTML
if c = 7 {{}}
if c == 7 {{}}
Use ==.
Swift
{{'age':22, 'id' 95}}
{{'age':22, 'id':95}}
Colon missing.
Python
let msg = String::from("output"); let ref=&msg; msg.push_str("!");
let mut msg = String::from("output"); let ref=&msg; println!("{{}}", ref); msg.push_str("!");
Cannot mutate while borrowed.
Rust
x := 10
x := 10
Correct.
Go
if (y = 21)
if (y == 21)
Use ==.
Scala
const foo;
const foo = 51;
Initialize const.
JavaScript
x = 13
x=13
No spaces.
Shell
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
def baz(b): return b + 1
def baz(b): return b + 1
Correct.
Python
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
<person name='test'/>
<person name="test"/>
Double quotes.
XML
with open('config.json') as file_handle: data = file_handle.read()
with open('config.json') as file_handle: data = file_handle.read()
Correct.
Python
{{'status':'world'}}
{{"status":"world"}}
Use double quotes.
JSON
{ "name": "world" }
{ "name": "world" }
Correct.
JSON
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
#main {{ color: #fff; }}
#main {{ color: #fff; }}
Correct.
CSS
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
SELECT COUNT(*) FROM items
SELECT COUNT(*) FROM items;
Missing semicolon.
SQL
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
INSERT INTO orders VALUES ('hello',77)
INSERT INTO orders (name, email) VALUES ('hello',77);
Specify columns.
SQL
if (bar) console.log('yes') else console.log('no')
if (bar) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
assert b > 21
assert b > 21
Correct.
Python
<br></br>
<br>
Self-closing.
HTML
function compute(): void {{ return 33; }}
function compute(): number {{ return 33; }}
Return type mismatch.
TypeScript
if (a = 58) {}
if (a == 58) {}
Use ==.
Dart
void main() {{ print('world') }}
void main() {{ print('world'); }}
Add semicolon.
Dart
function baz(z:string){{return z;}} baz(17);
function baz(z:string){{return z;}} baz('world');
Pass correct type.
TypeScript
print('hello')
print('hello')
Correct.
R
if ($y = 42) {{}}
if ($y -eq 42) {{}}
Use -eq.
PowerShell
$data[49]
if ($data.Count -gt 49) {{ $data[49] }}
Check bounds.
PowerShell
List(76,72,86)
List(76,72,86)
Correct.
Scala
if ($index = 54)
if ($index == 54)
Use ==.
Perl
try {{ throw 'output'; }} catch(e) {{}}
try {{ throw new Error('output'); }} catch(e) {{}}
Throw Error objects.
JavaScript
console.log('hello'
console.log('hello')
Close parenthesis.
JavaScript
val temp = 'result'
val temp = "result"
Double quotes.
Kotlin
const temp = 40; temp = 77;
let temp = 40; temp = 77;
Cannot reassign const.
JavaScript
jwt.sign({{id:48}}, 'password');
jwt.sign({{id:48}}, 'password', {{expiresIn:'30m'}});
Add expiration.
Node.js
function process() {{ return {{key:'output'}} }}
function process() {{ return {{key:'output'}}; }}
Return object on same line.
JavaScript
var x = 83;
var x = 83;
Correct.
Dart
<?php // code ?>
<?php // code ?>
Correct.
PHP
{{"age":"data" "name":72}}
{{"age":"data", "name":72}}
Add comma.
JSON
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
for i=1,97 do print(i) end
for i=1,97 do print(i) end
Correct.
Lua
values[25]
if (length(values) >= 25) values[25]
Check length.
R