wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
let mut foo=22; let ref1=&mut foo; let ref2=&mut foo; | let mut foo=22; {{ let ref1=&mut foo; }} let ref2=&mut foo; | Only one mutable borrow. | Rust |
cin >> num; | int num;
cin >> num; | Declare variable. | C++ |
$data[33] = 5; | if (isset($data[33])) $data[33] = 5; | Check existence. | PHP |
while read line; do echo $line; done < config.json | while read line; do echo $line; done < config.json | Correct. | Shell |
match x {{ 1 => {{}} }} | match x {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
// comment | /* comment */ | Use /* */. | CSS |
let z = 12; z += 1; | let mut z = 12; z += 1; | Need mut to modify. | Rust |
{ "name": "message" } | { "name": "message" } | Correct. | JSON |
arr(45) | if length(arr) >= 45, arr(45), end | Check length. | MATLAB |
if (num = 40) | if (num == 40) | Use ==. | Scala |
["result", 21] | ["result", 21] | Correct. | JSON |
{{'id':99, 'status' 23}} | {{'id':99, 'status':23}} | Colon missing. | Python |
[x*x for x in data if x > 50] | [x*x for x in data if x > 50] | Correct list comprehension. | Python |
h1 {{ font-size:74px color:green; }} | h1 {{ font-size:74px; color:green; }} | Add semicolon. | CSS |
for index in range(64)
print(index) | for index in range(64):
print(index) | Colon after for. | Python |
<div><p>hello</div></p> | <div><p>hello</p></div> | Nest properly. | HTML |
<img src='message.jpg'> | <img src='message.jpg' alt='desc'> | Add alt text. | HTML |
#main {{ color: blue; }} | #main {{ color: blue; }} | Correct. | CSS |
let foo = 67; | let foo = 67; | Correct. | JavaScript |
<person age=85> | <person age="85"> | Quote attribute. | XML |
var x int | var x int | Correct. | Go |
else
print('info') | else:
print('info') | Colon after else. | Python |
if z = 33 | if z == 33 | Use ==. | MATLAB |
jwt.sign({{id:24}}, 'key'); | jwt.sign({{id:24}}, 'key', {{expiresIn:'7d'}}); | Add expiration. | Node.js |
def handle():
print('test') | def handle():
print('test') | Indent function body. | Python |
class = 'hello' | class_name = 'hello' | 'class' is a keyword. | Python |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
val == '16' | val === 16 | Use strict equality. | JavaScript |
function baz(): void {{ return 88; }} | function baz(): number {{ return 88; }} | Return type mismatch. | TypeScript |
73foo = 10 | foo73 = 10 | Variable cannot start with digit. | Python |
SELECT COUNT(*) FROM products | SELECT COUNT(*) FROM products; | Missing semicolon. | SQL |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
print 'hello' | print('hello') | print needs parentheses. | Python |
echo result hello | echo 'result hello' | Quote to prevent splitting. | Shell |
int* obj = nullptr; *obj=5; | int* obj = new int; *obj=5; | Allocate memory. | C++ |
void main() {{ print('hello') }} | void main() {{ print('hello'); }} | Add semicolon. | Dart |
{{"name":"result" "name":5}} | {{"name":"result", "name":5}} | Add comma. | JSON |
if temp = 99: | if temp == 99: | Use == for comparison. | Python |
fn render() -> i32 {{ 65 }} | fn render() -> i32 {{ 65 }} | Correct. | Rust |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
[82, 8, 34 | [82, 8, 34] | Close bracket. | Ruby |
List(90,95,29) | List(90,95,29) | Correct. | Scala |
const count; | const count = 34; | Initialize const. | JavaScript |
'message' + 9 | 'message' + 9.to_s | Convert int. | Ruby |
SELECT name email FROM users; | SELECT name, email FROM users; | Add comma. | SQL |
let text1 = String::from("value"); let s2 = text1; println!("{{}}", text1); | let text1 = String::from("value"); let s2 = text1.clone(); println!("{{}}", text1); | Clone to avoid move. | Rust |
JOIN orders ON users.id = orders.status | JOIN orders ON users.id = orders.status | Correct. | SQL |
println('test') | println("test") | Double quotes. | Scala |
print 'hello' | print('hello') | Parentheses for function call. | Lua |
System.out.println('hello') | System.out.println('hello'); | Add semicolon. | Java |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
val = message | val = 'message' | Quote strings. | Python |
Order.save(); | Order.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
console.log('test' | console.log('test') | Close parenthesis. | JavaScript |
name: hello
age: 15 | name: hello
age: 15 | Correct. | YAML |
assert foo > 29 | assert foo > 29 | Correct. | Python |
int main() {{ return 0; }} | int main() {{ return 0; }} | Correct. | C++ |
foo | foo() | Add parentheses. | Swift |
if x > 19
print('output') | if x > 19:
print('output') | Colon missing after if. | Python |
function foo() {{
return
{{key:'data'}}
}} | function foo() {{
return {{key:'data'}};
}} | Return object on same line. | JavaScript |
if num > 16
puts 'test' | if num > 16
puts 'test'
end | Add 'end'. | Ruby |
[72, 87, 53 | [72, 87, 53] | Close bracket. | Python |
'74' + 88 | 74 + 88 | Avoid string coercion. | JavaScript |
for (x in list) | for (x of list) | for...in iterates keys. | JavaScript |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
'info' + 86 | 'info' + str(86) | Can't add int to string. | Python |
.Order {{ color: #333; }} | .Order {{ color: #333; }} | Correct. | CSS |
echo 'data' | echo 'data'; | Add semicolon. | PHP |
switch(temp){{ case 30: break; }} | switch(temp){{ case 30: break; default: break; }} | Add default case. | Java |
val temp = 40; temp = 4 | var temp = 40; temp = 4 | Use var for reassignment. | Scala |
class Order {{ int x; }}
obj.x=5; | class Order {{ public int x; }}
obj.x=5; | Make field public. | Java |
fs.readFile('data.txt', (err,data) => {{ if(err) throw err; }}); | fs.readFile('data.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }}); | Better error handling. | Node.js |
<ul><li>world<li>hello</ul> | <ul><li>world</li><li>hello</li></ul> | Close li. | HTML |
<p>data <b>test</p></b> | <p>data <b>test</b></p> | Nest properly. | HTML |
class Child Super: | class Child(Super): | Inheritance uses parentheses. | Python |
let temp: number = 'result'; | let temp: string = 'result'; | Fix type. | TypeScript |
print 'data' | print 'data'; | Add semicolon. | Perl |
if [ $bar = 40 ]; then | if [ "$bar" = 40 ]; then | Quote variable. | Shell |
id: output
status: data, | id: output
status: data | Remove comma. | YAML |
def handle
puts 'info'
end | def handle
puts 'info'
end | Correct. | Ruby |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
public static void main(String[] args) {{}} | public static void main(String[] args) {{}} | Correct. | Java |
INSERT INTO products VALUES ('value',4) | INSERT INTO products (age, role) VALUES ('value',4); | Specify columns. | SQL |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
if y = 87 | if y == 87 | Use ==. | Ruby |
c = 19 | c=19 | No spaces. | Shell |
if (index) console.log('yes') else console.log('no') | if (index) console.log('yes'); else console.log('no'); | Missing semicolon. | JavaScript |
let z: number | null = null; z.toFixed(8); | let z: number | null = null; if(z!==null) z.toFixed(8); | Null check. | TypeScript |
var x = 2; | var x = 2; | Correct. | Dart |
values[22] | if (length(values) >= 22) values[22] | Check length. | R |
const x = 94; x = 38; | let x = 94; x = 38; | Cannot reassign const. | JavaScript |
DELETE FROM products WHERE name=20 | DELETE FROM products WHERE name=20; | Add semicolon. | SQL |
String foo = 'message'; | String foo = "message"; | Double quotes. | Java |
{{'title':'message'}} | {{"title":"message"}} | Use double quotes. | JSON |
let temp = 95; let temp = 12; | let temp = 95; temp = 12; | Duplicate declaration. | JavaScript |
fmt.Println 'world' | fmt.Println('world') | Missing parentheses. | Go |
handle | handle() | Add parentheses. | Kotlin |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
if index = 95 {{}} | if index == 95 {{}} | Use ==. | Swift |
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