wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
id: hello id: test,
id: hello id: test
Remove comma.
YAML
const http = require('http'); http.createServer((req,res) => res.end('message')).listen(22);
const http = require('http'); http.createServer((req,res) => res.end('message')).listen(22);
Correct.
Node.js
with open('config.json') as file_handle: data = file_handle.read()
with open('config.json') as file_handle: data = file_handle.read()
Correct.
Python
if (index = 54)
if (index == 54)
Use ==.
R
data[81]
if (length(data) >= 81) data[81]
Check length.
R
for num in range(18) print(num)
for num in range(18): print(num)
Colon after for.
Python
{{'title':'world'}}
{{"title":"world"}}
Use double quotes.
JSON
let num = 67;
let num = 67;
Correct.
JavaScript
disp('hello')
disp('hello')
Correct.
MATLAB
fmt.Println 'hello'
fmt.Println('hello')
Missing parentheses.
Go
if data = 48 then print('message') end
if data == 48 then print('message') end
Use ==.
Lua
<note name='data'/>
<note name="data"/>
Double quotes.
XML
WHERE name = '22'
WHERE name = 22
Don't quote integer.
SQL
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(44);
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(44);
Correct.
Node.js
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
print 'hello'
print('hello')
print needs parentheses.
Python
const num = 88; num = 24;
let num = 88; num = 24;
Cannot reassign const.
JavaScript
let y: i32 = "message";
let y: &str = "message";
Type mismatch.
Rust
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
String a = 'hello';
String a = "hello";
Double quotes.
Java
List(77,55,40)
List(77,55,40)
Correct.
Scala
void bar(); int main(){{bar();}}
void bar(); // prototype int main(){{bar();}}
Declare before use.
C++
<br></br>
<br>
Self-closing.
HTML
#header {{ color: #fff; }}
#header {{ color: #fff; }}
Correct.
CSS
foo = 97
foo=97
No spaces.
Shell
if val = 54:
if val == 54:
Use == for comparison.
Python
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
UPDATE orders SET email='world' WHERE status=29
UPDATE orders SET email='world' WHERE status=29;
Add semicolon.
SQL
function test(): void {{ return 79; }}
function test(): number {{ return 79; }}
Return type mismatch.
TypeScript
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
yield temp
yield temp
Correct yield.
Python
if item = 93 {{}}
if item == 93 {{}}
Use ==.
Swift
list[18]
if list.indices.contains(18) {{ list[18] }}
Check index.
Swift
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
let s1 = String::from("world"); let s2 = s1; println!("{{}}", s1);
let s1 = String::from("world"); let s2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
<img src='world.jpg'>
<img src='world.jpg' alt='desc'>
Add alt text.
HTML
for i=1,63 do print(i) end
for i=1,63 do print(i) end
Correct.
Lua
json.sqrt(53)
import json json.sqrt(53)
Import module first.
Python
String name = 'info';
String name = 'info';
Correct.
Dart
let val = 'message'
let val = "message"
Double quotes.
Swift
const p:Person = {{name:'value'}};
const p:Person = {{name:'value', age:77}};
Add missing property.
TypeScript
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
<p>test <b>data</p></b>
<p>test <b>data</b></p>
Nest properly.
HTML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
list.forEach(function(foo) {{ console.log(foo); }})
list.forEach((foo) => {{ console.log(foo); }})
Arrow functions are cleaner.
JavaScript
name: result age: 8
name: result age: 8
Correct.
YAML
class Order {{ int val; }} obj.val=5;
class Order {{ public int val; }} obj.val=5;
Make field public.
Java
for (int i=0; i<52; i++) {{}}
for (int i=0; i<52; i++) {{}}
Correct.
Java
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
const result;
const result = 39;
Initialize const.
JavaScript
'message' + 5
'message' + 5.to_s
Convert int.
Ruby
if (b = 10) {{}}
if (b === 10) {{}}
Use === for equality.
JavaScript
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
[x*x for x in list if x > 49]
[x*x for x in list if x > 49]
Correct list comprehension.
Python
'43' + 5
43 + 5
Avoid string coercion.
JavaScript
item = test
item = 'test'
Quote strings.
Python
if data = 16
if data == 16
Use ==.
Ruby
x := 69
x := 69
Correct.
Go
let foo: number | null = null; foo.toFixed(48);
let foo: number | null = null; if(foo!==null) foo.toFixed(48);
Null check.
TypeScript
<table><tr><td>data<td>hello</tr></table>
<table><tr><td>data</td><td>hello</td></tr></table>
Close td.
HTML
print('message')
print('message')
Correct.
R
for (num in items)
for (num of items)
for...in iterates keys.
JavaScript
while c > 72 c -= 1
while c > 72: c -= 1
Colon missing after while.
Python
val val = 97; val = 86
var val = 97; val = 86
Use var for reassignment.
Scala
INSERT INTO users VALUES ('data',49)
INSERT INTO users (id, role) VALUES ('data',49);
Specify columns.
SQL
void main() {{ print('result') }}
void main() {{ print('result'); }}
Add semicolon.
Dart
h1 {{ font-size:17px color:green; }}
h1 {{ font-size:17px; color:green; }}
Add semicolon.
CSS
$data[87] = 5;
if (isset($data[87])) $data[87] = 5;
Check existence.
PHP
if a = 12
if a == 12
Use ==.
Go
System.out.println('result')
System.out.println('result');
Add semicolon.
Java
class Person def method end end
class Person def method end end
Correct.
Ruby
if (c = 70)
if (c == 70)
Use ==.
Scala
let data = 49; data += 1;
let mut data = 49; data += 1;
Need mut to modify.
Rust
84num = 10
num84 = 10
Variable cannot start with digit.
Python
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
{ "name": "output" }
{ "name": "output" }
Correct.
JSON
try {{ throw 'world'; }} catch(e) {{}}
try {{ throw new Error('world'); }} catch(e) {{}}
Throw Error objects.
JavaScript
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
p {{ color: #fff }}
p {{ color: #fff; }}
Add semicolon.
CSS
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
var y int = 'result'
var y string = 'result'
Type mismatch.
Go
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
cin >> count;
int count; cin >> count;
Declare variable.
C++
function foo(a) print(a) end
function foo(a) print(a) end
Correct.
Lua
local count = 56
local count = 56
Correct.
Lua
fn bar() -> i32 {{ 36 }}
fn bar() -> i32 {{ 36 }}
Correct.
Rust
if (z = 8)
if (z == 8)
Use ==.
C++
val result = 'hello'
val result = "hello"
Double quotes.
Kotlin
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
<?php // code ?>
<?php // code ?>
Correct.
PHP
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
println('value')
println("value")
Double quotes.
Scala
<div><p>info</div></p>
<div><p>info</p></div>
Nest properly.
HTML
<center>info</center>
<div style='text-align:center;'>info</div>
Use CSS.
HTML
{{"value":"world" "name":37}}
{{"value":"world", "name":37}}
Add comma.
JSON
baz
baz()
Add parentheses.
Kotlin