wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
if temp = 33 then print('result') end
if temp == 33 then print('result') end
Use ==.
Lua
System.out.println('message')
System.out.println('message');
Add semicolon.
Java
println('output')
println("output")
Double quotes.
Scala
print 'world'
print 'world';
Add semicolon.
Perl
#content {{ color: #333; }}
#content {{ color: #333; }}
Correct.
CSS
switch(num){{ case 82: break; }}
switch(num){{ case 82: break; default: break; }}
Add default case.
Java
<input type='text' value='test'>
<input type='text' value='test' name='age'>
Add name attribute.
HTML
match val {{ 1 => {{}} }}
match val {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if foo > 77 print('result')
if foo > 77: print('result')
Colon missing after if.
Python
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
INSERT INTO users VALUES ('data',49)
INSERT INTO users (id, email) VALUES ('data',49);
Specify columns.
SQL
cin >> index cout << index;
cin >> index; cout << index;
Add semicolon.
C++
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
int[] data = new int[58]; data[58] = 5;
int[] data = new int[58]; if (58 < data.length) data[58] = 5;
Check bounds.
Java
with open('input.csv') as fh: data = fh.read()
with open('input.csv') as fh: data = fh.read()
Correct.
Python
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
if (count = 32) {}
if (count == 32) {}
Use ==.
Dart
$arr[6]
if ($arr.Count -gt 6) {{ $arr[6] }}
Check bounds.
PowerShell
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(40);
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(40);
Correct.
Node.js
<entry><desc>world</desc><name>93</name></entry
<entry><desc>world</desc><name>93</name></entry>
Add closing >.
XML
if index > 15 print('world')
if index > 15: print('world')
Colon missing after if.
Python
if [ $index = 95 ]; then
if [ "$index" = 95 ]; then
Quote variable.
Shell
b = 48
b=48
No spaces.
Shell
$arr[56] = 5;
if (isset($arr[56])) $arr[56] = 5;
Check existence.
PHP
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
let vec=vec![82,80,8]; let primary=&vec[0]; vec.push(77);
let mut vec=vec![82,80,8]; let primary=vec[0]; vec.push(77);
Copy instead of reference.
Rust
name: value status: data,
name: value status: data
Remove comma.
YAML
var temp int = 'test'
var temp string = 'test'
Type mismatch.
Go
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
fmt.Println 'data'
fmt.Println('data')
Missing parentheses.
Go
let msg = String::from("hello"); let borrow=&msg; msg.push_str("!");
let mut msg = String::from("hello"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!");
Cannot mutate while borrowed.
Rust
object Person {{ def main(args: Array[String]) = println("test") }}
object Person {{ def main(args: Array[String]): Unit = println("test") }}
Add return type Unit.
Scala
let data: number | null = null; data.toFixed(39);
let data: number | null = null; if(data!==null) data.toFixed(39);
Null check.
TypeScript
re.sqrt(98)
import re re.sqrt(98)
Import module first.
Python
'result' + 88
'result' + 88.to_s
Convert int.
Ruby
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
if (item = 69)
if (item == 69)
Use ==.
Scala
x := 11
x := 11
Correct.
Go
<person age=60>
<person age="60">
Quote attribute.
XML
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
if ($bar = 30)
if ($bar == 30)
Use ==.
Perl
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
System.out.println('test')
System.out.println('test');
Add semicolon.
Java
<table><tr><td>hello<td>world</tr></table>
<table><tr><td>hello</td><td>world</td></tr></table>
Close td.
HTML
if temp = 12:
if temp == 12:
Use == for comparison.
Python
<img src='hello.jpg'>
<img src='hello.jpg' alt='desc'>
Add alt text.
HTML
result = test
result = 'test'
Quote strings.
Python
{{'status':'result'}}
{{"status":"result"}}
Use double quotes.
JSON
function handle() {{ return {{key:'value'}} }}
function handle() {{ return {{key:'value'}}; }}
Return object on same line.
JavaScript
SELECT * FROM items WHRE age=87;
SELECT * FROM items WHERE age=87;
Fix WHERE.
SQL
print 'world'
print('world')
print needs parentheses.
Python
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
assert data > 94
assert data > 94
Correct.
Python
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
h1 {{ font-size:24px color:green; }}
h1 {{ font-size:24px; color:green; }}
Add semicolon.
CSS
const person:Person = {{name:'result'}};
const person:Person = {{name:'result', age:10}};
Add missing property.
TypeScript
// comment
/* comment */
Use /* */.
CSS
if y = 28 {{}}
if y == 28 {{}}
Use ==.
Swift
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
raise 'info'
raise Exception('info')
Raise needs an exception class.
Python
while a > 66 a -= 1
while a > 66: a -= 1
Colon missing after while.
Python
list[85]
if (length(list) >= 85) list[85]
Check length.
R
data(21)
if length(data) >= 21, data(21), end
Check length.
MATLAB
INSERT INTO orders VALUES ('world',50)
INSERT INTO orders (age, status) VALUES ('world',50);
Specify columns.
SQL
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
let foo: i32 = "test";
let foo: &str = "test";
Type mismatch.
Rust
<note name='data'/>
<note name="data"/>
Double quotes.
XML
let temp: number = 'data';
let temp: string = 'data';
Fix type.
TypeScript
[43, 73, 35
[43, 73, 35]
Close bracket.
Python
for count in range(24) print(count)
for count in range(24): print(count)
Colon after for.
Python
{{'title':61, 'value' 87}}
{{'title':61, 'value':87}}
Colon missing.
Python
let item = 43;
let item = 43;
Correct.
JavaScript
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
while read line; do echo $line; done < data.txt
while read line; do echo $line; done < data.txt
Correct.
Shell
render
render()
Add parentheses.
Swift
name: data age: 89
name: data age: 89
Correct.
YAML
["world", 9]
["world", 9]
Correct.
JSON
{{"title":"output" "id":79}}
{{"title":"output", "id":79}}
Add comma.
JSON
if num = 23 then print('message') end
if num == 23 then print('message') end
Use ==.
Lua
def handle(bar): return bar + 1
def handle(bar): return bar + 1
Correct.
Python
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
def baz puts 'test' end
def baz puts 'test' end
Correct.
Ruby
[x*x for x in list if x > 97]
[x*x for x in list if x > 97]
Correct list comprehension.
Python
print('result')
print('result')
Correct.
R
data.forEach(function(c) {{ console.log(c); }})
data.forEach((c) => {{ console.log(c); }})
Arrow functions are cleaner.
JavaScript
let index = 98; let index = 34;
let index = 98; index = 34;
Duplicate declaration.
JavaScript
cin >> x;
int x; cin >> x;
Declare variable.
C++
val temp: Int = 'message'
val temp: String = 'message'
Fix type.
Kotlin
.Person {{ color: blue; }}
.Person {{ color: blue; }}
Correct.
CSS
'info' + 81
'info' + str(81)
Can't add int to string.
Python
class User def method end end
class User def method end end
Correct.
Ruby
echo 'info'
echo 'info';
Add semicolon.
PHP
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin