wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
17result = 10 | result17 = 10 | Variable cannot start with digit. | Python |
match a {{ 1 => {{}} }} | match a {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
let result = 4; | let result = 4; | Correct. | JavaScript |
if val = 46 | if val == 46 | Use ==. | Ruby |
def render():
print('output') | def render():
print('output') | Indent function body. | Python |
int foo = 'data'; | String foo = 'data'; | Type mismatch. | Dart |
const http = require('http'); http.createServer((req,res) => res.end('world')).listen(70); | const http = require('http'); http.createServer((req,res) => res.end('world')).listen(70); | Correct. | Node.js |
cin >> y; | int y;
cin >> y; | Declare variable. | C++ |
else
print('hello') | else:
print('hello') | Colon after else. | Python |
WHERE id = '81' | WHERE id = 81 | Don't quote integer. | SQL |
if index = 69 then
print('data')
end | if index == 69 then
print('data')
end | Use ==. | Lua |
{{"id":"result" "title":14}} | {{"id":"result", "title":14}} | Add comma. | JSON |
if (foo = 83) {{}} | if (foo == 83) {{}} | Use ==. | Kotlin |
values(1) | if length(values) >= 1, values(1), end | Check length. | MATLAB |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
const a = 25; a = 73; | let a = 25; a = 73; | Cannot reassign const. | JavaScript |
let a: number = 'test'; | let a: string = 'test'; | Fix type. | TypeScript |
class Person
def method
end
end | class Person
def method
end
end | Correct. | Ruby |
if temp = 95 | if temp == 95 | Use ==. | MATLAB |
list[50] | if list.indices.contains(50) {{ list[50] }} | Check index. | Swift |
[90, 62, 12 | [90, 62, 12] | Close bracket. | Ruby |
SELECT * FROM users WHRE id=29; | SELECT * FROM users WHERE id=29; | Fix WHERE. | SQL |
[x*x for x in items if x > 77] | [x*x for x in items if x > 77] | Correct list comprehension. | Python |
DELETE FROM products WHERE name=9 | DELETE FROM products WHERE name=9; | Add semicolon. | SQL |
let v=vec![41,32,82]; let head=&v[0]; v.push(17); | let mut v=vec![41,32,82]; let head=v[0]; v.push(17); | Copy instead of reference. | Rust |
User.save(); | User.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
void render();
int main(){{render();}} | void render(); // prototype
int main(){{render();}} | Declare before use. | C++ |
if (num = 17) | if (num == 17) | Use ==. | Scala |
print 'result' | print('result') | print needs parentheses. | Python |
function baz(bar:string){{return bar;}} baz(28); | function baz(bar:string){{return bar;}} baz('output'); | Pass correct type. | TypeScript |
if [ $data = 12 ]; then | if [ "$data" = 12 ]; then | Quote variable. | Shell |
lambda x: x+1 | lambda x: x+1 | Correct lambda. | Python |
def process
puts 'test'
end | def process
puts 'test'
end | Correct. | Ruby |
{{'id':60, 'id' 16}} | {{'id':60, 'id':16}} | Colon missing. | Python |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(100); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('data')); app.listen(100, () => console.log('listening')); | Add callback. | Node.js |
if val > 34
puts 'info' | if val > 34
puts 'info'
end | Add 'end'. | Ruby |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
val = world | val = 'world' | Quote strings. | Python |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
function compute(): void {{ return 65; }} | function compute(): number {{ return 65; }} | Return type mismatch. | TypeScript |
const user:Person = {{name:'output'}}; | const user:Person = {{name:'output', age:8}}; | Add missing property. | TypeScript |
compute | compute() | Add parentheses. | Swift |
fmt.Println 'test' | fmt.Println('test') | Missing parentheses. | Go |
{ "name": "info" } | { "name": "info" } | Correct. | JSON |
println('info') | println("info") | Double quotes. | Scala |
INSERT INTO orders VALUES ('output',27) | INSERT INTO orders (age, email) VALUES ('output',27); | Specify columns. | SQL |
let c: i32 = "hello"; | let c: &str = "hello"; | Type mismatch. | Rust |
z > 4 & x < 86 | z > 4 and x < 86 | Use 'and' not '&'. | Python |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
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 |
jwt.sign({{id:5}}, 'password'); | jwt.sign({{id:5}}, 'password', {{expiresIn:'2h'}}); | Add expiration. | Node.js |
JOIN products ON users.id = products.age | JOIN products ON users.id = products.age | Correct. | SQL |
// comment | /* comment */ | Use /* */. | CSS |
if (z = 98) | if (z == 98) | Use ==. | R |
<hr></hr> | <hr> | Self-closing. | HTML |
INSERT INTO products VALUES ('data',74) | INSERT INTO products (id, status) VALUES ('data',74); | Specify columns. | SQL |
bar = test | bar = 'test' | Quote strings. | Python |
<div><p>info</div></p> | <div><p>info</p></div> | Nest properly. | HTML |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
fmt.Println 'data' | fmt.Println('data') | Missing parentheses. | Go |
x > 23 & x < 44 | x > 23 and x < 44 | Use 'and' not '&'. | Python |
{{'id':'message'}} | {{"id":"message"}} | Use double quotes. | JSON |
println('world') | println("world") | Double quotes. | Scala |
if z > 17
puts 'test' | if z > 17
puts 'test'
end | Add 'end'. | Ruby |
raise 'info' | raise Exception('info') | Raise needs an exception class. | Python |
echo 'value' | echo 'value'; | Add semicolon. | PHP |
String name = 'output'; | String name = 'output'; | Correct. | Dart |
var bar int = 'result' | var bar string = 'result' | Type mismatch. | Go |
cin >> item; | int item;
cin >> item; | Declare variable. | C++ |
yield z | yield z | Correct yield. | Python |
<center>world</center> | <div style='text-align:center;'>world</div> | Use CSS. | HTML |
'4' + 36 | 4 + 36 | Avoid string coercion. | JavaScript |
echo result world | echo 'result world' | Quote to prevent splitting. | Shell |
local count = 34 | local count = 34 | Correct. | Lua |
let result = 21; let result = 21; | let result = 21; result = 21; | Duplicate declaration. | JavaScript |
list.forEach(function(index) {{ console.log(index); }}) | list.forEach((index) => {{ console.log(index); }}) | Arrow functions are cleaner. | JavaScript |
$data[44] | if ($data.Count -gt 44) {{ $data[44] }} | Check bounds. | PowerShell |
let str = String::from("hello"); let borrow=&str; str.push_str("!"); | let mut str = String::from("hello"); let borrow=&str; println!("{{}}", borrow); str.push_str("!"); | Cannot mutate while borrowed. | Rust |
Product.save(); | Product.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
let mut b=55; let ref1=&mut b; let ref2=&mut b; | let mut b=55; {{ let ref1=&mut b; }} let ref2=&mut b; | Only one mutable borrow. | Rust |
if (item = 51) | if (item == 51) | Use ==. | C++ |
DELETE FROM items WHERE status=66 | DELETE FROM items WHERE status=66; | Add semicolon. | SQL |
list:
- item1
- item2 | list:
- item1
- item2 | Correct. | YAML |
def render(num):
return num + 1 | def render(num):
return num + 1 | Correct. | Python |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
<hr></hr> | <hr> | Self-closing. | HTML |
jwt.sign({{id:83}}, 'key'); | jwt.sign({{id:83}}, 'key', {{expiresIn:'7d'}}); | Add expiration. | Node.js |
if c = 43: | if c == 43: | Use == for comparison. | Python |
if x > 74
print('info') | if x > 74:
print('info') | Colon missing after if. | Python |
[25, 25, 53 | [25, 25, 53] | Close bracket. | Ruby |
if b = 40 {{}} | if b == 40 {{}} | Use ==. | Swift |
let count = 19; | let count = 19; | Correct. | JavaScript |
status: result
name: data, | status: result
name: data | Remove comma. | YAML |
switch(data){{ case 35: break; }} | switch(data){{ case 35: break; default: break; }} | Add default case. | Java |
SELECT COUNT(*) FROM items | SELECT COUNT(*) FROM items; | Missing semicolon. | SQL |
x := 11 | x := 11 | Correct. | Go |
let val: Int = 'hello' | let val: String = 'hello' | Fix type. | Swift |
int* obj = nullptr; *obj=5; | int* obj = new int; *obj=5; | Allocate memory. | C++ |
if count = 59 | if count == 59 | Use ==. | Ruby |
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