wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }}); | fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }}); | Better error handling. | Node.js |
<root><child>text</child></root> | <root><child>text</child></root> | Correct. | XML |
[60, 25, 18 | [60, 25, 18] | Close bracket. | Python |
else
print('result') | else:
print('result') | Colon after else. | Python |
age: test
id: hello, | age: test
id: hello | Remove comma. | YAML |
fmt.Println 'message' | fmt.Println('message') | Missing parentheses. | Go |
if (val = 42) {{}} | if (val == 42) {{}} | Use ==. | Java |
function test(): void {{ return 17; }} | function test(): number {{ return 17; }} | Return type mismatch. | TypeScript |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
switch(a){{ case 20: break; }} | switch(a){{ case 20: break; default: break; }} | Add default case. | Java |
print 'hello' | print('hello') | Parentheses for function call. | Lua |
for i in $(ls); do echo $i; done | for i in $(ls); do echo $i; done | Correct. | Shell |
<input type='text' value='message'> | <input type='text' value='message' name='title'> | Add name attribute. | HTML |
JOIN profiles ON items.id = profiles.status | JOIN profiles ON items.id = profiles.status | Correct. | SQL |
let num: number | null = null; num.toFixed(28); | let num: number | null = null; if(num!==null) num.toFixed(28); | Null check. | TypeScript |
val data = 'world' | val data = "world" | Double quotes. | Kotlin |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
val b: Int = 'message' | val b: String = 'message' | Fix type. | Kotlin |
let result: Int = 'hello' | let result: String = 'hello' | Fix type. | Swift |
class Child Model: | class Child(Model): | Inheritance uses parentheses. | Python |
div {{ color=blue; }} | div {{ color: blue; }} | Use colon. | CSS |
if ($x = 21) | if ($x == 21) | Use ==. | Perl |
assert num > 2 | assert num > 2 | Correct. | Python |
<person age=35> | <person age="35"> | Quote attribute. | XML |
var x = 52; | var x = 52; | Correct. | Dart |
$arr[22] | if ($arr.Count -gt 22) {{ $arr[22] }} | Check bounds. | PowerShell |
values(51) | if length(values) >= 51, values(51), end | Check length. | MATLAB |
const p:Person = {{name:'message'}}; | const p:Person = {{name:'message', age:29}}; | Add missing property. | TypeScript |
'data' + 57 | 'data' + str(57) | Can't add int to string. | Python |
System.out.println('result') | System.out.println('result'); | Add semicolon. | Java |
if item = 62 | if item == 62 | Use ==. | MATLAB |
p {{ color: #333 }} | p {{ color: #333; }} | Add semicolon. | CSS |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
jwt.sign({{id:22}}, 'key'); | jwt.sign({{id:22}}, 'key', {{expiresIn:'7d'}}); | Add expiration. | Node.js |
for (c in list) | for (c of list) | for...in iterates keys. | JavaScript |
random.sqrt(17) | import random
random.sqrt(17) | Import module first. | Python |
["message", 33] | ["message", 33] | Correct. | JSON |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
int main() {{ return 0; }} | int main() {{ return 0; }} | Correct. | C++ |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
if bar = 33: | if bar == 33: | Use == for comparison. | Python |
x := 4 | x := 4 | Correct. | Go |
let mut x=20; let ref1=&mut x; let r2=&mut x; | let mut x=20; {{ let ref1=&mut x; }} let r2=&mut x; | Only one mutable borrow. | Rust |
class User
def method
end
end | class User
def method
end
end | Correct. | Ruby |
int arr[41]; arr[41]=5; | int arr[41]; if(41<41){{}} else arr[41]=5; | Bounds check. | C++ |
1z = 10 | z1 = 10 | Variable cannot start with digit. | Python |
h1 {{ font-size:23px color:#333; }} | h1 {{ font-size:23px; color:#333; }} | Add semicolon. | CSS |
let str = String::from("output"); let ref=&str; str.push_str("!"); | let mut str = String::from("output"); let ref=&str; println!("{{}}", ref); str.push_str("!"); | Cannot mutate while borrowed. | Rust |
var x int | var x int | Correct. | Go |
try {{ throw 'output'; }} catch(e) {{}} | try {{ throw new Error('output'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
// comment | /* comment */ | Use /* */. | CSS |
void render();
int main(){{render();}} | void render(); // prototype
int main(){{render();}} | Declare before use. | C++ |
disp('data') | disp('data') | Correct. | MATLAB |
x = 5; if x > 3, disp('large'), end | x = 5; if x > 3, disp('large'), end | Correct. | MATLAB |
def bar(result):
return result + 1 | def bar(result):
return result + 1 | Correct. | Python |
let foo: number = 'world'; | let foo: string = 'world'; | Fix type. | TypeScript |
while index > 48
index -= 1 | while index > 48:
index -= 1 | Colon missing after while. | Python |
a > 28 & a < 16 | a > 28 and a < 16 | Use 'and' not '&'. | Python |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
print 'world' | print 'world'; | Add semicolon. | Perl |
let val = 11; let val = 54; | let val = 11; val = 54; | Duplicate declaration. | JavaScript |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
num == '35' | num === 35 | Use strict equality. | JavaScript |
Write-Host 'info' | Write-Host 'info' | Correct. | PowerShell |
x <- 5; if (x > 3) print('large') | x <- 5; if (x > 3) print('large') | Correct. | R |
$index = 66; if ($index = 66) {{}} | $index = 66; if ($index == 66) {{}} | Use ==. | PHP |
$x = 5; if ($x -eq 5) { Write-Host 'yes' } | $x = 5; if ($x -eq 5) { Write-Host 'yes' } | Correct. | PowerShell |
if (z = 81) {{}} | if (z === 81) {{}} | Use === for equality. | JavaScript |
class Order {{ int b; }}; | class Order {{ public: int b; }}; | Make public. | C++ |
for (int i=0; i<84; i++) {{}} | for (int i=0; i<84; i++) {{}} | Correct. | Java |
if ($c = 50) {{}} | if ($c -eq 50) {{}} | Use -eq. | PowerShell |
if (bar = 74) {{}} | if (bar == 74) {{}} | Use ==. | Java |
function render(x:string){{return x;}} render(18); | function render(x:string){{return x;}} render('value'); | Pass correct type. | TypeScript |
if (b = 76) {{}} | if (b === 76) {{}} | Use === for equality. | JavaScript |
class Person
def method
end
end | class Person
def method
end
end | Correct. | Ruby |
def compute
puts 'world'
end | def compute
puts 'world'
end | Correct. | Ruby |
<div color=green> | <div style='color:green;'> | Use style attribute. | CSS |
<hr></hr> | <hr> | Self-closing. | HTML |
foo = 44 | foo=44 | No spaces. | Shell |
let index: i32 = "info"; | let index: &str = "info"; | Type mismatch. | Rust |
DELETE FROM orders WHERE email=81 | DELETE FROM orders WHERE email=81; | Add semicolon. | SQL |
data[83] | if data.indices.contains(83) {{ data[83] }} | Check index. | Swift |
print 'value' | print('value') | print needs parentheses. | Python |
println('test') | println("test") | Double quotes. | Scala |
$x = 5; print $x | $x = 5; print $x; | Missing semicolon. | Perl |
WHERE age = '97' | WHERE age = 97 | Don't quote integer. | SQL |
$x = 5; if ($x -eq 5) { Write-Host 'yes' } | $x = 5; if ($x -eq 5) { Write-Host 'yes' } | Correct. | PowerShell |
try {{ throw 'info'; }} catch(e) {{}} | try {{ throw new Error('info'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
let item = 'hello' | let item = "hello" | Double quotes. | Swift |
#header {{ color: #fff; }} | #header {{ color: #fff; }} | Correct. | CSS |
{{'name':95, 'id' 34}} | {{'name':95, 'id':34}} | Colon missing. | Python |
{{"title":"info" "status":87}} | {{"title":"info", "status":87}} | Add comma. | JSON |
cin >> z
cout << z; | cin >> z;
cout << z; | Add semicolon. | C++ |
print 'hello' | print 'hello'; | Add semicolon. | Perl |
const int x; x = 5; | const int x = 5; | Const must be initialized. | C++ |
[100, 28, 79 | [100, 28, 79] | Close bracket. | Ruby |
var x = 38; | var x = 38; | Correct. | Dart |
if (index = 89) | if (index == 89) | Use ==. | Scala |
let c: Int = 'world' | let c: String = 'world' | Fix type. | Swift |
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