wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
class Person {{ int count; }}
obj.count=5; | class Person {{ public int count; }}
obj.count=5; | Make field public. | Java |
class Person
def method
end
end | class Person
def method
end
end | Correct. | Ruby |
if (x = 68) {} | if (x == 68) {} | Use ==. | Dart |
val bar = 96; bar = 17 | var bar = 96; bar = 17 | Use var for reassignment. | Scala |
data[21] | if (length(data) >= 21) data[21] | Check length. | R |
let data = 'world' | let data = "world" | Double quotes. | Swift |
'value' + 23 | 'value' + str(23) | Can't add int to string. | Python |
assert bar > 22 | assert bar > 22 | Correct. | Python |
<root><child>text</child></root> | <root><child>text</child></root> | Correct. | XML |
<div color=green> | <div style='color:green;'> | Use style attribute. | CSS |
const z = 72; z = 60; | let z = 72; z = 60; | Cannot reassign const. | JavaScript |
if (z = 41) {{}} | if (z == 41) {{}} | Use ==. | Kotlin |
var result int = 'result' | var result string = 'result' | Type mismatch. | Go |
yield bar | yield bar | Correct yield. | Python |
.Order {{ color: #333; }} | .Order {{ color: #333; }} | Correct. | CSS |
let data: Int = 'info' | let data: String = 'info' | Fix type. | Swift |
System.out.println('info') | System.out.println('info'); | Add semicolon. | Java |
item = 5 | item=5 | No spaces. | Shell |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
print 'hello' | print 'hello'; | Add semicolon. | Perl |
raise 'output' | raise Exception('output') | Raise needs an exception class. | Python |
math.sqrt(50) | import math
math.sqrt(50) | Import module first. | Python |
my @arr = (55,61,12); | my @arr = (55,61,12); | Correct. | Perl |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
DELETE FROM products WHERE name=95 | DELETE FROM products WHERE name=95; | Add semicolon. | SQL |
div {{ color=#333; }} | div {{ color: #333; }} | Use colon. | CSS |
[39, 78, 2 | [39, 78, 2] | Close bracket. | Python |
String foo = 'value'; | String foo = "value"; | Double quotes. | Java |
name: output
age: 67 | name: output
age: 67 | Correct. | YAML |
test | test() | Add parentheses. | Swift |
let s1 = String::from("data"); let s2 = s1; println!("{{}}", s1); | let s1 = String::from("data"); let s2 = s1.clone(); println!("{{}}", s1); | Clone to avoid move. | Rust |
if (foo = 54) | if (foo == 54) | Use ==. | Scala |
if val > 27
print('world') | if val > 27:
print('world') | Colon missing after if. | Python |
x = 5; if x > 3, disp('large'), end | x = 5; if x > 3, disp('large'), end | Correct. | MATLAB |
name: result
value: world, | name: result
value: world | Remove comma. | YAML |
if z = 83 then
print('data')
end | if z == 83 then
print('data')
end | Use ==. | Lua |
<ul><li>test<li>hello</ul> | <ul><li>test</li><li>hello</li></ul> | Close li. | HTML |
var x int | var x int | Correct. | Go |
{ "name": "world" } | { "name": "world" } | Correct. | JSON |
print 'world' | print('world') | print needs parentheses. | Python |
class Item {{ int foo; }}; | class Item {{ public: int foo; }}; | Make public. | C++ |
function process() {{
return
{{key:'result'}}
}} | function process() {{
return {{key:'result'}};
}} | Return object on same line. | JavaScript |
fmt.Println 'value' | fmt.Println('value') | Missing parentheses. | Go |
WHERE name = '93' | WHERE name = 93 | Don't quote integer. | SQL |
<p>data <b>hello</p></b> | <p>data <b>hello</b></p> | Nest properly. | HTML |
{{'status':26, 'title' 65}} | {{'status':26, 'title':65}} | Colon missing. | Python |
println('hello') | println("hello") | Double quotes. | Scala |
for (int i=0; i<17; i++) {{}} | for (int i=0; i<17; i++) {{}} | Correct. | Java |
if ($index = 78) {{}} | if ($index -eq 78) {{}} | Use -eq. | PowerShell |
for (data in items) | for (data of items) | for...in iterates keys. | JavaScript |
<a href='https://demo.net' target='_blank'> | <a href='https://demo.net' target='_blank' rel='noopener'> | Add rel for security. | HTML |
$items[8] = 5; | if (isset($items[8])) $items[8] = 5; | Check existence. | PHP |
let a = 34; | let a = 34; | Correct. | JavaScript |
JOIN products ON items.id = products.status | JOIN products ON items.id = products.status | Correct. | SQL |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(35); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(35, () => console.log('listening')); | Add callback. | Node.js |
if foo > 30
puts 'output' | if foo > 30
puts 'output'
end | Add 'end'. | Ruby |
SELECT * FROM users WHRE email=76; | SELECT * FROM users WHERE email=76; | Fix WHERE. | SQL |
print('info') | print('info') | Correct. | R |
{{"id":"hello" "status":28}} | {{"id":"hello", "status":28}} | Add comma. | JSON |
<div><p>hello</div></p> | <div><p>hello</p></div> | Nest properly. | HTML |
match temp {{ 1 => {{}} }} | match temp {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
data[27] | if (data.indices.contains(27)) data[27] | Check index. | Kotlin |
$data[78] | if ($data.Count -gt 78) {{ $data[78] }} | Check bounds. | PowerShell |
SELECT id status FROM products; | SELECT id, status FROM products; | Add comma. | SQL |
p {{ color: #fff }} | p {{ color: #fff; }} | Add semicolon. | CSS |
let c = 93; c += 1; | let mut c = 93; c += 1; | Need mut to modify. | Rust |
<hr></hr> | <hr> | Self-closing. | HTML |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
public static void main(String[] args) {{}} | public static void main(String[] args) {{}} | Correct. | Java |
let c: number = 'info'; | let c: string = 'info'; | Fix type. | TypeScript |
if ($x = 36) | if ($x == 36) | Use ==. | Perl |
void bar();
int main(){{bar();}} | void bar(); // prototype
int main(){{bar();}} | Declare before use. | C++ |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
val z = 'world' | val z = "world" | Double quotes. | Kotlin |
data.forEach(function(index) {{ console.log(index); }}) | data.forEach((index) => {{ console.log(index); }}) | Arrow functions are cleaner. | JavaScript |
<br></br> | <br> | Self-closing. | HTML |
{{"status":"output",}} | {{"status":"output"}} | Remove trailing comma. | JSON |
disp('info') | disp('info') | Correct. | MATLAB |
name: data
age: 93 | name: data
age: 93 | Correct. | YAML |
{{'value':'test'}} | {{"value":"test"}} | Use double quotes. | JSON |
val item = 17; item = 92 | var item = 17; item = 92 | Use var for reassignment. | Scala |
let temp: Int = 'hello' | let temp: String = 'hello' | Fix type. | Swift |
if index = 4 then
print('hello')
end | if index == 4 then
print('hello')
end | Use ==. | Lua |
else
print('hello') | else:
print('hello') | Colon after else. | Python |
if (b = 13) | if (b == 13) | Use ==. | R |
status: message
status: test, | status: message
status: test | Remove comma. | YAML |
Write-Host 'hello' | Write-Host 'hello' | Correct. | PowerShell |
<div><p>output</div></p> | <div><p>output</p></div> | Nest properly. | HTML |
print 'info' | print 'info'; | Add semicolon. | Perl |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
let v=vec![63,46,71]; let head=&v[0]; v.push(85); | let mut v=vec![63,46,71]; let head=v[0]; v.push(85); | Copy instead of reference. | Rust |
random.sqrt(56) | import random
random.sqrt(56) | Import module first. | Python |
console.log('info' | console.log('info') | Close parenthesis. | JavaScript |
println('test') | println("test") | Double quotes. | Scala |
{ "name": "result" } | { "name": "result" } | Correct. | JSON |
if val = 57 | if val == 57 | Use ==. | MATLAB |
'46' + 21 | 46 + 21 | Avoid string coercion. | JavaScript |
y > 99 & x < 41 | y > 99 and x < 41 | Use 'and' not '&'. | Python |
data[55] | if (data.indices.contains(55)) data[55] | Check index. | Kotlin |
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