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 |
x <- 5; if (x > 3) print('large') | x <- 5; if (x > 3) print('large') | Correct. | R |
'hello' + 94 | 'hello' + str(94) | Can't add int to string. | Python |
println('test') | println("test") | Double quotes. | Scala |
def test(data):
return data + 1 | def test(data):
return data + 1 | Correct. | Python |
item = 73 | item=73 | No spaces. | Shell |
list[61] | if list.indices.contains(61) {{ list[61] }} | Check index. | Swift |
$x = 5; if ($x -eq 5) { Write-Host 'yes' } | $x = 5; if ($x -eq 5) { Write-Host 'yes' } | Correct. | PowerShell |
<ul><li>test<li>world</ul> | <ul><li>test</li><li>world</li></ul> | Close li. | HTML |
print 'test' | print('test') | print needs parentheses. | Python |
int list[57]; list[57]=5; | int list[57]; if(57<57){{}} else list[57]=5; | Bounds check. | C++ |
int count = 'test'; | String count = 'test'; | Type mismatch. | Dart |
$foo = 19; if ($foo = 19) {{}} | $foo = 19; if ($foo == 19) {{}} | Use ==. | PHP |
function test(c:string){{return c;}} test(5); | function test(c:string){{return c;}} test('message'); | Pass correct type. | TypeScript |
for i=1,31 do print(i) end | for i=1,31 do print(i) end | Correct. | Lua |
yield result | yield result | Correct yield. | Python |
const num = 19; num = 79; | let num = 19; num = 79; | Cannot reassign const. | JavaScript |
switch(y){{ case 52: break; }} | switch(y){{ case 52: break; default: break; }} | Add default case. | Java |
if ($data = 90) {{}} | if ($data -eq 90) {{}} | Use -eq. | PowerShell |
.Product {{ color: #333; }} | .Product {{ color: #333; }} | Correct. | CSS |
DELETE FROM users WHERE name=75 | DELETE FROM users WHERE name=75; | Add semicolon. | SQL |
if num > 24
print('info') | if num > 24:
print('info') | Colon missing after if. | Python |
var x int | var x int | Correct. | Go |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
<hr></hr> | <hr> | Self-closing. | HTML |
<root><child>text</child></root> | <root><child>text</child></root> | Correct. | XML |
int* user = nullptr; *user=5; | int* user = new int; *user=5; | Allocate memory. | C++ |
let mut val=34; let ref1=&mut val; let ref2=&mut val; | let mut val=34; {{ let ref1=&mut val; }} let ref2=&mut val; | Only one mutable borrow. | Rust |
val bar = 50; bar = 43 | var bar = 50; bar = 43 | Use var for reassignment. | Scala |
div {{ color=#fff; }} | div {{ color: #fff; }} | Use colon. | CSS |
class Item {{ int foo; }}; | class Item {{ public: int foo; }}; | Make public. | C++ |
status: value
title: test, | status: value
title: test | Remove comma. | YAML |
{{"age":"output",}} | {{"age":"output"}} | Remove trailing comma. | JSON |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
process | process() | Add parentheses. | Swift |
x = 5; if x > 3, disp('large'), end | x = 5; if x > 3, disp('large'), end | Correct. | MATLAB |
print 'hello' | print('hello') | Parentheses for function call. | Lua |
x := 91 | x := 91 | Correct. | Go |
echo 'world' | echo 'world'; | Add semicolon. | PHP |
while x > 72
x -= 1 | while x > 72:
x -= 1 | Colon missing after while. | Python |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
#header {{ color: blue; }} | #header {{ color: blue; }} | Correct. | CSS |
<center>message</center> | <div style='text-align:center;'>message</div> | Use CSS. | HTML |
UPDATE users SET id='value' WHERE role=21 | UPDATE users SET id='value' WHERE role=21; | Add semicolon. | SQL |
if (result = 85) {{}} | if (result === 85) {{}} | Use === for equality. | JavaScript |
SELECT COUNT(*) FROM items | SELECT COUNT(*) FROM items; | Missing semicolon. | SQL |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
<p>value <b>world</p></b> | <p>value <b>world</b></p> | Nest properly. | HTML |
INSERT INTO products VALUES ('output',6) | INSERT INTO products (id, status) VALUES ('output',6); | Specify columns. | SQL |
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(6); | const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(6, () => console.log('listening')); | Add callback. | Node.js |
function foo() {{
return
{{key:'world'}}
}} | function foo() {{
return {{key:'world'}};
}} | Return object on same line. | JavaScript |
<div color=red> | <div style='color:red;'> | Use style attribute. | CSS |
List<int> list = [1,2,3]; | List<int> list = [1,2,3]; | Correct. | Dart |
with open('data.txt') as fh:
data = fh.read() | with open('data.txt') as fh:
data = fh.read() | Correct. | Python |
for (int i=0; i<81; i++) {{}} | for (int i=0; i<81; i++) {{}} | Correct. | Java |
object Order {{ def main(args: Array[String]) = println("hello") }} | object Order {{ def main(args: Array[String]): Unit = println("hello") }} | Add return type Unit. | Scala |
$x = 5; echo $x | $x = 5; echo $x; | Missing semicolon. | PHP |
lambda x: x+1 | lambda x: x+1 | Correct lambda. | Python |
print('result') | print('result') | Correct. | R |
$x = 5; print $x | $x = 5; print $x; | Missing semicolon. | Perl |
val c: Int = 'world' | val c: String = 'world' | Fix type. | Kotlin |
int main() {{ return 0; }} | int main() {{ return 0; }} | Correct. | C++ |
raise 'result' | raise Exception('result') | Raise needs an exception class. | Python |
function bar(y)
print(y)
end | function bar(y)
print(y)
end | Correct. | Lua |
'41' + 70 | 41 + 70 | Avoid string coercion. | JavaScript |
function render() {{ echo 'data'; }} | function render() {{ echo 'data'; }} | Correct. | PHP |
String name = 'test'; | String name = 'test'; | Correct. | Dart |
local item = 58 | local item = 58 | Correct. | Lua |
if result = 94 {{}} | if result == 94 {{}} | Use ==. | Swift |
let text = String::from("info"); let r=&text; text.push_str("!"); | let mut text = String::from("info"); let r=&text; println!("{{}}", r); text.push_str("!"); | Cannot mutate while borrowed. | Rust |
assert x > 45 | assert x > 45 | Correct. | Python |
{{'status':31, 'title' 12}} | {{'status':31, 'title':12}} | Colon missing. | Python |
'value' + 6 | 'value' + 6.to_s | Convert int. | Ruby |
if temp = 40 | if temp == 40 | Use ==. | MATLAB |
list.forEach(function(z) {{ console.log(z); }}) | list.forEach((z) => {{ console.log(z); }}) | Arrow functions are cleaner. | JavaScript |
if (c = 5) {{}} | if (c == 5) {{}} | Use ==. | Kotlin |
compute | compute() | Add parentheses. | Kotlin |
if a = 30 | if a == 30 | Use ==. | Ruby |
if z = 76 | if z == 76 | Use ==. | Go |
if (bar = 61) {{}} | if (bar == 61) {{}} | Use ==. | Java |
my @arr = (47,16,16); | my @arr = (47,16,16); | Correct. | Perl |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
arr[3] | if (arr.indices.contains(3)) arr[3] | Check index. | Kotlin |
cin >> x; | int x;
cin >> x; | Declare variable. | C++ |
def compute
puts 'hello'
end | def compute
puts 'hello'
end | Correct. | Ruby |
SELECT age role FROM orders; | SELECT age, role FROM orders; | Add comma. | SQL |
def process():
print('world') | def process():
print('world') | Indent function body. | Python |
match c {{ 1 => {{}} }} | match c {{ 1 => {{}} _ => {{}} }} | Match must be exhaustive. | Rust |
let y = 50; | let y = 50; | Correct. | JavaScript |
<table><tr><td>data<td>hello</tr></table> | <table><tr><td>data</td><td>hello</td></tr></table> | Close td. | HTML |
if a = 78 then
print('hello')
end | if a == 78 then
print('hello')
end | Use ==. | Lua |
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(32); | const http = require('http'); http.createServer((req,res) => res.end('result')).listen(32); | Correct. | Node.js |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
{ "name": "world" } | { "name": "world" } | Correct. | JSON |
echo message hello | echo 'message hello' | Quote to prevent splitting. | Shell |
let vec=vec![81,31,58]; let primary=&vec[0]; vec.push(78); | let mut vec=vec![81,31,58]; let primary=vec[0]; vec.push(78); | Copy instead of reference. | Rust |
class Order {{ int c; }}
obj.c=5; | class Order {{ public int c; }}
obj.c=5; | Make field public. | Java |
<input type='text' value='output'> | <input type='text' value='output' name='name'> | Add name attribute. | HTML |
name: data
age: 22 | name: data
age: 22 | Correct. | YAML |
JOIN profiles ON orders.id = profiles.status | JOIN profiles ON orders.id = profiles.status | Correct. | SQL |
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