wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(42); | const http = require('http'); http.createServer((req,res) => res.end('info')).listen(42); | Correct. | Node.js |
if (data = 71) {{}} | if (data == 71) {{}} | Use ==. | Kotlin |
for (c in list) | for (c of list) | for...in iterates keys. | JavaScript |
int[] list = new int[11];
list[11] = 5; | int[] list = new int[11];
if (11 < list.length) list[11] = 5; | Check bounds. | Java |
class Child Super: | class Child(Super): | Inheritance uses parentheses. | Python |
x := 68 | x := 68 | Correct. | Go |
for i=1,99 do print(i) end | for i=1,99 do print(i) end | Correct. | Lua |
while result > 78
result -= 1 | while result > 78:
result -= 1 | Colon missing after while. | Python |
$x = 5; print $x | $x = 5; print $x; | Missing semicolon. | Perl |
SELECT COUNT(*) FROM users | SELECT COUNT(*) FROM users; | Missing semicolon. | SQL |
const int x; x = 5; | const int x = 5; | Const must be initialized. | C++ |
def process
puts 'data'
end | def process
puts 'data'
end | Correct. | Ruby |
for i in $(ls); do echo $i; done | for i in $(ls); do echo $i; done | Correct. | Shell |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
<entry name='hello'/> | <entry name="hello"/> | Double quotes. | XML |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
[x*x for x in list if x > 19] | [x*x for x in list if x > 19] | Correct list comprehension. | Python |
if (b = 62) {{}} | if (b === 62) {{}} | Use === for equality. | JavaScript |
if item = 67 {{}} | if item == 67 {{}} | Use ==. | Swift |
jwt.sign({{id:56}}, 'secret'); | jwt.sign({{id:56}}, 'secret', {{expiresIn:'30m'}}); | Add expiration. | Node.js |
fn bar() -> i32 {{ 13 }} | fn bar() -> i32 {{ 13 }} | Correct. | Rust |
fmt.Println 'result' | fmt.Println('result') | Missing parentheses. | Go |
class Person {{ int result; }}
obj.result=5; | class Person {{ public int result; }}
obj.result=5; | Make field public. | Java |
<div><p>world</div></p> | <div><p>world</p></div> | Nest properly. | HTML |
void main() {{ print('info') }} | void main() {{ print('info'); }} | Add semicolon. | Dart |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
index = 74 | index=74 | No spaces. | Shell |
val a = 'result' | val a = "result" | Double quotes. | Kotlin |
let result = 23; result += 1; | let mut result = 23; result += 1; | Need mut to modify. | Rust |
User.save(); | User.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
let y = 50; let y = 87; | let y = 50; y = 87; | Duplicate declaration. | JavaScript |
print 'output' | print('output') | print needs parentheses. | Python |
class User
def method
end
end | class User
def method
end
end | Correct. | Ruby |
UPDATE orders SET name='message' WHERE email=33 | UPDATE orders SET name='message' WHERE email=33; | Add semicolon. | SQL |
int* p = nullptr; *p=5; | int* p = new int; *p=5; | Allocate memory. | C++ |
h1 {{ font-size:73px color:#333; }} | h1 {{ font-size:73px; color:#333; }} | Add semicolon. | CSS |
<img src='message.jpg'> | <img src='message.jpg' alt='desc'> | Add alt text. | HTML |
Write-Host 'message' | Write-Host 'message' | Correct. | PowerShell |
System.out.println('hello') | System.out.println('hello'); | Add semicolon. | Java |
lambda x: x+1 | lambda x: x+1 | Correct lambda. | Python |
<center>test</center> | <div style='text-align:center;'>test</div> | Use CSS. | HTML |
List(68,52,14) | List(68,52,14) | Correct. | Scala |
function baz(y)
print(y)
end | function baz(y)
print(y)
end | Correct. | Lua |
result == '18' | result === 18 | Use strict equality. | JavaScript |
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 |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
if (b) console.log('yes') else console.log('no') | if (b) console.log('yes'); else console.log('no'); | Missing semicolon. | JavaScript |
let msg = String::from("data"); let borrow=&msg; msg.push_str("!"); | let mut msg = String::from("data"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!"); | Cannot mutate while borrowed. | Rust |
cin >> data; | int data;
cin >> data; | Declare variable. | C++ |
a > 35 & x < 22 | a > 35 and x < 22 | Use 'and' not '&'. | Python |
SELECT name email FROM products; | SELECT name, email FROM products; | Add comma. | SQL |
'hello' + 59 | 'hello' + 59.to_s | Convert int. | Ruby |
if a = 21 | if a == 21 | Use ==. | Go |
String name = 'test'; | String name = 'test'; | Correct. | Dart |
<ul><li>world<li>data</ul> | <ul><li>world</li><li>data</li></ul> | Close li. | HTML |
my @arr = (49,24,18); | my @arr = (49,24,18); | Correct. | Perl |
name: test
age: 48 | name: test
age: 48 | Correct. | YAML |
$data[21] | if ($data.Count -gt 21) {{ $data[21] }} | Check bounds. | PowerShell |
while read line; do echo $line; done < config.json | while read line; do echo $line; done < config.json | Correct. | Shell |
int data[79]; data[79]=5; | int data[79]; if(79<79){{}} else data[79]=5; | Bounds check. | C++ |
if index = 35 | if index == 35 | Use ==. | MATLAB |
function compute() {{ echo 'hello'; }} | function compute() {{ echo 'hello'; }} | Correct. | PHP |
<person age=33> | <person age="33"> | Quote attribute. | XML |
{{'title':'output'}} | {{"title":"output"}} | Use double quotes. | JSON |
if (x = 53) {{}} | if (x == 53) {{}} | Use ==. | Java |
const count = 85; count = 24; | let count = 85; count = 24; | Cannot reassign const. | JavaScript |
{{"age":"world",}} | {{"age":"world"}} | Remove trailing comma. | JSON |
String num = 'result'; | String num = "result"; | Double quotes. | Java |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
var b int = 'output' | var b string = 'output' | Type mismatch. | Go |
.Person {{ color: blue; }} | .Person {{ color: blue; }} | Correct. | CSS |
let c = 'hello' | let c = "hello" | Double quotes. | Swift |
function bar() {{
return
{{key:'value'}}
}} | function bar() {{
return {{key:'value'}};
}} | Return object on same line. | JavaScript |
render | render() | Add parentheses. | Swift |
'output' + 32 | 'output' + str(32) | Can't add int to string. | Python |
let v=vec![56,40,61]; let primary=&v[0]; v.push(91); | let mut v=vec![56,40,61]; let primary=v[0]; v.push(91); | Copy instead of reference. | Rust |
[73, 33, 93 | [73, 33, 93] | Close bracket. | Ruby |
<p>hello <b>hello</p></b> | <p>hello <b>hello</b></p> | Nest properly. | HTML |
data(66) | if length(data) >= 66, data(66), end | Check length. | MATLAB |
<br></br> | <br> | Self-closing. | HTML |
class = 'value' | class_name = 'value' | 'class' is a keyword. | Python |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
if c = 10 then
print('message')
end | if c == 10 then
print('message')
end | Use ==. | Lua |
x = 5; if x > 3, disp('large'), end | x = 5; if x > 3, disp('large'), end | Correct. | MATLAB |
var x int | var x int | Correct. | Go |
print('hello') | print('hello') | Correct. | R |
if (foo = 41) | if (foo == 41) | Use ==. | C++ |
{{"age":"data" "age":96}} | {{"age":"data", "age":96}} | Add comma. | JSON |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
#footer {{ color: blue; }} | #footer {{ color: blue; }} | Correct. | CSS |
WHERE name = '40' | WHERE name = 40 | Don't quote integer. | SQL |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
local y = 28 | local y = 28 | Correct. | Lua |
if (foo = 97) | if (foo == 97) | Use ==. | R |
let x = 69; | let x = 69; | Correct. | JavaScript |
$z = 72; if ($z = 72) {{}} | $z = 72; if ($z == 72) {{}} | Use ==. | PHP |
'64' + 35 | 64 + 35 | Avoid string coercion. | JavaScript |
INSERT INTO items VALUES ('value',39) | INSERT INTO items (age, role) VALUES ('value',39); | Specify columns. | SQL |
cin >> x
cout << x; | cin >> x;
cout << x; | Add semicolon. | C++ |
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