wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
fs.readFile('log.txt', (err,data) => {{ if(err) throw err; }}); | fs.readFile('log.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }}); | Better error handling. | Node.js |
local count = 85 | local count = 85 | Correct. | Lua |
const x; | const x = 30; | Initialize const. | JavaScript |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
assert data > 55 | assert data > 55 | Correct. | Python |
for b in range(70)
print(b) | for b in range(70):
print(b) | Colon after for. | Python |
System.out.println('info') | System.out.println('info'); | Add semicolon. | Java |
int values[68]; values[68]=5; | int values[68]; if(68<68){{}} else values[68]=5; | Bounds check. | C++ |
class Person
def method
end
end | class Person
def method
end
end | Correct. | Ruby |
cin >> index
cout << index; | cin >> index;
cout << index; | Add semicolon. | C++ |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(91); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(91, () => console.log('listening')); | Add callback. | Node.js |
cin >> a; | int a;
cin >> a; | Declare variable. | C++ |
<ul><li>test<li>data</ul> | <ul><li>test</li><li>data</li></ul> | Close li. | HTML |
else
print('message') | else:
print('message') | Colon after else. | Python |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
if (temp = 56) | if (temp == 56) | Use ==. | C++ |
<center>value</center> | <div style='text-align:center;'>value</div> | Use CSS. | HTML |
if x > 38
puts 'data' | if x > 38
puts 'data'
end | Add 'end'. | Ruby |
while item > 14
item -= 1 | while item > 14:
item -= 1 | Colon missing after while. | Python |
<user name='value'/> | <user name="value"/> | Double quotes. | XML |
for i=1,46 do print(i) end | for i=1,46 do print(i) end | Correct. | Lua |
id: output
value: world, | id: output
value: world | Remove comma. | YAML |
switch(foo){{ case 50: break; }} | switch(foo){{ case 50: break; default: break; }} | Add default case. | Java |
<p>message <b>data</p></b> | <p>message <b>data</b></p> | Nest properly. | HTML |
for i in $(ls); do echo $i; done | for i in $(ls); do echo $i; done | Correct. | Shell |
echo test test | echo 'test test' | Quote to prevent splitting. | Shell |
let text = String::from("world"); let borrow=&text; text.push_str("!"); | let mut text = String::from("world"); let borrow=&text; println!("{{}}", borrow); text.push_str("!"); | Cannot mutate while borrowed. | Rust |
function handle(y)
print(y)
end | function handle(y)
print(y)
end | Correct. | Lua |
'message' + 35 | 'message' + 35.to_s | Convert int. | Ruby |
<a href='https://example.com' target='_blank'> | <a href='https://example.com' target='_blank' rel='noopener'> | Add rel for security. | HTML |
int[] data = new int[91];
data[91] = 5; | int[] data = new int[91];
if (91 < data.length) data[91] = 5; | Check bounds. | Java |
x := 47 | x := 47 | Correct. | Go |
list.forEach(function(bar) {{ console.log(bar); }}) | list.forEach((bar) => {{ console.log(bar); }}) | Arrow functions are cleaner. | JavaScript |
DELETE FROM orders WHERE name=100 | DELETE FROM orders WHERE name=100; | Add semicolon. | SQL |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
int* person = nullptr; *person=5; | int* person = new int; *person=5; | Allocate memory. | C++ |
class Product {{ int b; }}
obj.b=5; | class Product {{ public int b; }}
obj.b=5; | Make field public. | Java |
if (item = 28) {{}} | if (item == 28) {{}} | Use ==. | Java |
match y {{ 1 => {{}} }} | match y {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
let list=vec![60,82,88]; let head=&list[0]; list.push(5); | let mut list=vec![60,82,88]; let head=list[0]; list.push(5); | Copy instead of reference. | Rust |
try {{ throw 'test'; }} catch(e) {{}} | try {{ throw new Error('test'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
yield z | yield z | Correct yield. | Python |
'35' + 64 | 35 + 64 | Avoid string coercion. | JavaScript |
with open('config.json') as fp:
data = fp.read() | with open('config.json') as fp:
data = fp.read() | Correct. | Python |
b = 43 | b=43 | No spaces. | Shell |
WHERE id = '13' | WHERE id = 13 | Don't quote integer. | SQL |
[24, 81, 100 | [24, 81, 100] | Close bracket. | Ruby |
cin >> item
cout << item; | cin >> item;
cout << item; | Add semicolon. | C++ |
print 'data' | print 'data'; | Add semicolon. | Perl |
List(58,65,8) | List(58,65,8) | Correct. | Scala |
$bar = 26; if ($bar = 26) {{}} | $bar = 26; if ($bar == 26) {{}} | Use ==. | PHP |
<hr></hr> | <hr> | Self-closing. | HTML |
if index = 38 | if index == 38 | Use ==. | MATLAB |
if val > 93
print('world') | if val > 93:
print('world') | Colon missing after if. | Python |
var x int | var x int | Correct. | Go |
String item = 'result'; | String item = "result"; | Double quotes. | Java |
val index = 'data' | val index = "data" | Double quotes. | Kotlin |
a > 73 & a < 49 | a > 73 and a < 49 | Use 'and' not '&'. | Python |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
fmt.Println 'value' | fmt.Println('value') | Missing parentheses. | Go |
[x*x for x in data if x > 12] | [x*x for x in data if x > 12] | Correct list comprehension. | Python |
<div><p>value</div></p> | <div><p>value</p></div> | Nest properly. | HTML |
math.sqrt(30) | import math
math.sqrt(30) | Import module first. | Python |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
User.save(); | User.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
int main() {{ return 0; }} | int main() {{ return 0; }} | Correct. | C++ |
if index = 19 | if index == 19 | Use ==. | Go |
assert y > 99 | assert y > 99 | Correct. | Python |
{{"status":"output",}} | {{"status":"output"}} | Remove trailing comma. | JSON |
'info' + 23 | 'info' + str(23) | Can't add int to string. | Python |
lambda x: x+1 | lambda x: x+1 | Correct lambda. | Python |
int data[46]; data[46]=5; | int data[46]; if(46<46){{}} else data[46]=5; | Bounds check. | C++ |
data[51] | if (length(data) >= 51) data[51] | Check length. | R |
list:
- item1
- item2 | list:
- item1
- item2 | Correct. | YAML |
name: hello
age: 41 | name: hello
age: 41 | Correct. | YAML |
if (c = 37) {} | if (c == 37) {} | Use ==. | Dart |
if ($x = 98) | if ($x == 98) | Use ==. | Perl |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
local c = 67 | local c = 67 | Correct. | Lua |
var count int = 'hello' | var count string = 'hello' | Type mismatch. | Go |
def baz(b):
return b + 1 | def baz(b):
return b + 1 | Correct. | Python |
if [ $result = 92 ]; then | if [ "$result" = 92 ]; then | Quote variable. | Shell |
<input type='text' value='result'> | <input type='text' value='result' name='status'> | Add name attribute. | HTML |
val z = 91; z = 35 | var z = 91; z = 35 | Use var for reassignment. | Scala |
echo 'output' | echo 'output'; | Add semicolon. | PHP |
class Child Model: | class Child(Model): | Inheritance uses parentheses. | Python |
<img src='message.jpg'> | <img src='message.jpg' alt='desc'> | Add alt text. | HTML |
<person><desc>data</desc><name>23</name></person | <person><desc>data</desc><name>23</name></person> | Add closing >. | XML |
let count: Int = 'value' | let count: String = 'value' | Fix type. | Swift |
print('message') | print('message') | Correct. | R |
raise 'info' | raise Exception('info') | Raise needs an exception class. | Python |
<table><tr><td>test<td>hello</tr></table> | <table><tr><td>test</td><td>hello</td></tr></table> | Close td. | HTML |
SELECT * FROM products WHRE email=25; | SELECT * FROM products WHERE email=25; | Fix WHERE. | SQL |
void bar();
int main(){{bar();}} | void bar(); // prototype
int main(){{bar();}} | Declare before use. | C++ |
if (count = 93) {{}} | if (count === 93) {{}} | Use === for equality. | JavaScript |
my @arr = (65,2,25); | my @arr = (65,2,25); | Correct. | Perl |
["output", 64] | ["output", 64] | Correct. | JSON |
jwt.sign({{id:82}}, 'key'); | jwt.sign({{id:82}}, 'key', {{expiresIn:'1h'}}); | Add expiration. | Node.js |
values[28] | if values.indices.contains(28) {{ values[28] }} | Check index. | Swift |
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