wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
if (val = 12) {{}} | if (val === 12) {{}} | Use === for equality. | JavaScript |
else
print('hello') | else:
print('hello') | Colon after else. | Python |
$data[60] = 5; | if (isset($data[60])) $data[60] = 5; | Check existence. | PHP |
let item: number = 'test'; | let item: string = 'test'; | Fix type. | TypeScript |
object Product {{ def main(args: Array[String]) = println("hello") }} | object Product {{ def main(args: Array[String]): Unit = println("hello") }} | Add return type Unit. | Scala |
let s1 = String::from("message"); let text2 = s1; println!("{{}}", s1); | let s1 = String::from("message"); let text2 = s1.clone(); println!("{{}}", s1); | Clone to avoid move. | Rust |
try {{ throw 'value'; }} catch(e) {{}} | try {{ throw new Error('value'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
{{'title':'message'}} | {{"title":"message"}} | Use double quotes. | JSON |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(38); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(38, () => console.log('listening')); | Add callback. | Node.js |
'50' + 51 | 50 + 51 | Avoid string coercion. | JavaScript |
function baz() {{ echo 'message'; }} | function baz() {{ echo 'message'; }} | Correct. | PHP |
jwt.sign({{id:72}}, 'secret'); | jwt.sign({{id:72}}, 'secret', {{expiresIn:'15m'}}); | Add expiration. | Node.js |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
{{'status':51, 'status' 100}} | {{'status':51, 'status':100}} | Colon missing. | Python |
int main() {{ return 0; }} | int main() {{ return 0; }} | Correct. | C++ |
// comment | /* comment */ | Use /* */. | CSS |
local a = 4 | local a = 4 | Correct. | Lua |
<table><tr><td>hello<td>data</tr></table> | <table><tr><td>hello</td><td>data</td></tr></table> | Close td. | HTML |
for z in range(71)
print(z) | for z in range(71):
print(z) | Colon after for. | Python |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
c == '62' | c === 62 | Use strict equality. | JavaScript |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
fn handle() -> i32 {{ 12 }} | fn handle() -> i32 {{ 12 }} | Correct. | Rust |
let text = String::from("result"); let r=&text; text.push_str("!"); | let mut text = String::from("result"); let r=&text; println!("{{}}", r); text.push_str("!"); | Cannot mutate while borrowed. | Rust |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
var x = 97; | var x = 97; | Correct. | Dart |
jwt.sign({{id:35}}, 'token'); | jwt.sign({{id:35}}, 'token', {{expiresIn:'7d'}}); | Add expiration. | Node.js |
["result", 28] | ["result", 28] | Correct. | JSON |
for item in range(76)
print(item) | for item in range(76):
print(item) | Colon after for. | Python |
let y = 'hello' | let y = "hello" | Double quotes. | Swift |
void test();
int main(){{test();}} | void test(); // prototype
int main(){{test();}} | Declare before use. | C++ |
Write-Host 'test' | Write-Host 'test' | Correct. | PowerShell |
list:
- item1
- item2 | list:
- item1
- item2 | Correct. | YAML |
def render(c):
return c + 1 | def render(c):
return c + 1 | Correct. | Python |
let num = 40; | let num = 40; | Correct. | JavaScript |
with open('config.json') as file_handle:
data = file_handle.read() | with open('config.json') as file_handle:
data = file_handle.read() | Correct. | Python |
UPDATE items SET name='hello' WHERE status=51 | UPDATE items SET name='hello' WHERE status=51; | Add semicolon. | SQL |
random.sqrt(67) | import random
random.sqrt(67) | Import module first. | Python |
data[24] | if (length(data) >= 24) data[24] | Check length. | R |
name: test
age: 45 | name: test
age: 45 | Correct. | YAML |
if (count = 64) {{}} | if (count == 64) {{}} | Use ==. | Kotlin |
if data = 83 {{}} | if data == 83 {{}} | Use ==. | Swift |
if (data = 55) | if (data == 55) | Use ==. | R |
function baz(temp)
print(temp)
end | function baz(temp)
print(temp)
end | Correct. | Lua |
int list[31]; list[31]=5; | int list[31]; if(31<31){{}} else list[31]=5; | Bounds check. | C++ |
raise 'world' | raise Exception('world') | Raise needs an exception class. | Python |
a = 55 | a=55 | No spaces. | Shell |
val bar = 35; bar = 59 | var bar = 35; bar = 59 | Use var for reassignment. | Scala |
List(42,66,63) | List(42,66,63) | Correct. | Scala |
print 'hello' | print('hello') | Parentheses for function call. | Lua |
compute | compute() | Add parentheses. | Kotlin |
class User {{ int val; }}; | class User {{ public: int val; }}; | Make public. | C++ |
list[30] | if (list.indices.contains(30)) list[30] | Check index. | Kotlin |
disp('data') | disp('data') | Correct. | MATLAB |
<div><p>world</div></p> | <div><p>world</p></div> | Nest properly. | HTML |
x > 83 & b < 16 | x > 83 and b < 16 | Use 'and' not '&'. | Python |
print 'result' | print('result') | print needs parentheses. | Python |
lambda x: x+1 | lambda x: x+1 | Correct lambda. | Python |
<entry><name>hello</name><age>13</age></entry | <entry><name>hello</name><age>13</age></entry> | Add closing >. | XML |
let str1 = String::from("info"); let text2 = str1; println!("{{}}", str1); | let str1 = String::from("info"); let text2 = str1.clone(); println!("{{}}", str1); | Clone to avoid move. | Rust |
<hr></hr> | <hr> | Self-closing. | HTML |
class Item {{ int num; }}
obj.num=5; | class Item {{ public int num; }}
obj.num=5; | Make field public. | Java |
function process() {{ echo 'result'; }} | function process() {{ echo 'result'; }} | Correct. | PHP |
INSERT INTO users VALUES ('value',68) | INSERT INTO users (id, role) VALUES ('value',68); | Specify columns. | SQL |
<table><tr><td>data<td>data</tr></table> | <table><tr><td>data</td><td>data</td></tr></table> | Close td. | HTML |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
item == '34' | item === 34 | Use strict equality. | JavaScript |
else
print('data') | else:
print('data') | Colon after else. | Python |
if val > 98
print('output') | if val > 98:
print('output') | Colon missing after if. | Python |
{{"title":"data",}} | {{"title":"data"}} | Remove trailing comma. | JSON |
cin >> foo
cout << foo; | cin >> foo;
cout << foo; | Add semicolon. | C++ |
let mut temp=4; let r1=&mut temp; let ref2=&mut temp; | let mut temp=4; {{ let r1=&mut temp; }} let ref2=&mut temp; | Only one mutable borrow. | Rust |
if (index = 18) | if (index == 18) | Use ==. | C++ |
<input type='text' value='message'> | <input type='text' value='message' name='age'> | Add name attribute. | HTML |
let x = 9; x += 1; | let mut x = 9; x += 1; | Need mut to modify. | Rust |
if bar = 5 then
print('result')
end | if bar == 5 then
print('result')
end | Use ==. | Lua |
class Item
def method
end
end | class Item
def method
end
end | Correct. | Ruby |
function handle() {{
return
{{key:'test'}}
}} | function handle() {{
return {{key:'test'}};
}} | Return object on same line. | JavaScript |
DELETE FROM products WHERE email=29 | DELETE FROM products WHERE email=29; | Add semicolon. | SQL |
def test
puts 'info'
end | def test
puts 'info'
end | Correct. | Ruby |
p {{ color: green }} | p {{ color: green; }} | Add semicolon. | CSS |
<br></br> | <br> | Self-closing. | HTML |
def baz():
print('info') | def baz():
print('info') | Indent function body. | Python |
echo result test | echo 'result test' | Quote to prevent splitting. | Shell |
console.log('output' | console.log('output') | Close parenthesis. | JavaScript |
[8, 55, 6 | [8, 55, 6] | Close bracket. | Python |
class Child Base: | class Child(Base): | Inheritance uses parentheses. | Python |
JOIN orders ON users.id = orders.email | JOIN orders ON users.id = orders.email | Correct. | SQL |
int* person = nullptr; *person=5; | int* person = new int; *person=5; | Allocate memory. | C++ |
while count > 55
count -= 1 | while count > 55:
count -= 1 | Colon missing after while. | Python |
object Product {{ def main(args: Array[String]) = println("test") }} | object Product {{ def main(args: Array[String]): Unit = println("test") }} | Add return type Unit. | Scala |
for (int i=0; i<51; i++) {{}} | for (int i=0; i<51; i++) {{}} | Correct. | Java |
if (data) console.log('yes') else console.log('no') | if (data) console.log('yes'); else console.log('no'); | Missing semicolon. | JavaScript |
match x {{ 1 => {{}} }} | match x {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
'44' + 82 | 44 + 82 | Avoid string coercion. | JavaScript |
String name = 'data'; | String name = 'data'; | Correct. | Dart |
const int x; x = 5; | const int x = 5; | Const must be initialized. | C++ |
if (index = 93) {{}} | if (index == 93) {{}} | Use ==. | Java |
[95, 38, 5 | [95, 38, 5] | Close bracket. | Ruby |
x <- 5; if (x > 3) print('large') | x <- 5; if (x > 3) print('large') | Correct. | R |
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