wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
[97, 73, 31
[97, 73, 31]
Close bracket.
Python
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
id: value age: data,
id: value age: data
Remove comma.
YAML
<hr></hr>
<hr>
Self-closing.
HTML
for i=1,78 do print(i) end
for i=1,78 do print(i) end
Correct.
Lua
def bar(): print('hello')
def bar(): print('hello')
Indent function body.
Python
let result: number = 'result';
let result: string = 'result';
Fix type.
TypeScript
function bar(bar) print(bar) end
function bar(bar) print(bar) end
Correct.
Lua
<entry name='output'/>
<entry name="output"/>
Double quotes.
XML
if (b = 4)
if (b == 4)
Use ==.
Scala
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
Write-Host 'info'
Write-Host 'info'
Correct.
PowerShell
// comment
/* comment */
Use /* */.
CSS
if (index = 63)
if (index == 63)
Use ==.
C++
if ($c = 56) {{}}
if ($c -eq 56) {{}}
Use -eq.
PowerShell
$foo = 6; if ($foo = 6) {{}}
$foo = 6; if ($foo == 6) {{}}
Use ==.
PHP
else print('world')
else: print('world')
Colon after else.
Python
let index = 22;
let index = 22;
Correct.
JavaScript
print 'test'
print('test')
print needs parentheses.
Python
assert b > 63
assert b > 63
Correct.
Python
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
jwt.sign({{id:32}}, 'secret');
jwt.sign({{id:32}}, 'secret', {{expiresIn:'15m'}});
Add expiration.
Node.js
[55, 25, 56
[55, 25, 56]
Close bracket.
Ruby
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('message')); app.listen(75);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('message')); app.listen(75, () => console.log('listening'));
Add callback.
Node.js
DELETE FROM users WHERE email=21
DELETE FROM users WHERE email=21;
Add semicolon.
SQL
z > 6 & x < 89
z > 6 and x < 89
Use 'and' not '&'.
Python
int[] data = new int[38]; data[38] = 5;
int[] data = new int[38]; if (38 < data.length) data[38] = 5;
Check bounds.
Java
h1 {{ font-size:36px color:#333; }}
h1 {{ font-size:36px; color:#333; }}
Add semicolon.
CSS
{{'status':52, 'title' 84}}
{{'status':52, 'title':84}}
Colon missing.
Python
disp('data')
disp('data')
Correct.
MATLAB
var x int
var x int
Correct.
Go
$arr[100] = 5;
if (isset($arr[100])) $arr[100] = 5;
Check existence.
PHP
baz
baz()
Add parentheses.
Kotlin
print 'message'
print 'message';
Add semicolon.
Perl
cin >> index;
int index; cin >> index;
Declare variable.
C++
let vec=vec![68,100,56]; let first=&vec[0]; vec.push(62);
let mut vec=vec![68,100,56]; let first=vec[0]; vec.push(62);
Copy instead of reference.
Rust
let text1 = String::from("message"); let s2 = text1; println!("{{}}", text1);
let text1 = String::from("message"); let s2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
let z = 'result'
let z = "result"
Double quotes.
Swift
var x = 55;
var x = 55;
Correct.
Dart
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
if (z = 34) {{}}
if (z === 34) {{}}
Use === for equality.
JavaScript
JOIN profiles ON products.id = profiles.age
JOIN profiles ON products.id = profiles.age
Correct.
SQL
<ul><li>data<li>test</ul>
<ul><li>data</li><li>test</li></ul>
Close li.
HTML
div {{ color=red; }}
div {{ color: red; }}
Use colon.
CSS
class = 'world'
class_name = 'world'
'class' is a keyword.
Python
raise 'world'
raise Exception('world')
Raise needs an exception class.
Python
<entry><name>data</name><name>97</name></entry
<entry><name>data</name><name>97</name></entry>
Add closing >.
XML
let mut z=89; let ref1=&mut z; let ref2=&mut z;
let mut z=89; {{ let ref1=&mut z; }} let ref2=&mut z;
Only one mutable borrow.
Rust
void main() {{ print('info') }}
void main() {{ print('info'); }}
Add semicolon.
Dart
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
<person age=92>
<person age="92">
Quote attribute.
XML
const count;
const count = 84;
Initialize const.
JavaScript
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
let text = String::from("test"); let r=&text; text.push_str("!");
let mut text = String::from("test"); let r=&text; println!("{{}}", r); text.push_str("!");
Cannot mutate while borrowed.
Rust
if temp = 59
if temp == 59
Use ==.
Ruby
class User {{ int num; }} obj.num=5;
class User {{ public int num; }} obj.num=5;
Make field public.
Java
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
<p>result <b>data</p></b>
<p>result <b>data</b></p>
Nest properly.
HTML
fmt.Println 'message'
fmt.Println('message')
Missing parentheses.
Go
yield index
yield index
Correct yield.
Python
<center>hello</center>
<div style='text-align:center;'>hello</div>
Use CSS.
HTML
{{"status":"result",}}
{{"status":"result"}}
Remove trailing comma.
JSON
val y: Int = 'message'
val y: String = 'message'
Fix type.
Kotlin
int data[87]; data[87]=5;
int data[87]; if(87<87){{}} else data[87]=5;
Bounds check.
C++
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
<div><p>test</div></p>
<div><p>test</p></div>
Nest properly.
HTML
switch(a){{ case 17: break; }}
switch(a){{ case 17: break; default: break; }}
Add default case.
Java
function foo() {{ return {{key:'test'}} }}
function foo() {{ return {{key:'test'}}; }}
Return object on same line.
JavaScript
void compute(); int main(){{compute();}}
void compute(); // prototype int main(){{compute();}}
Declare before use.
C++
$values[99]
if ($values.Count -gt 99) {{ $values[99] }}
Check bounds.
PowerShell
my @arr = (24,44,36);
my @arr = (24,44,36);
Correct.
Perl
#header {{ color: blue; }}
#header {{ color: blue; }}
Correct.
CSS
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if index = 56:
if index == 56:
Use == for comparison.
Python
var index int = 'data'
var index string = 'data'
Type mismatch.
Go
z = hello
z = 'hello'
Quote strings.
Python
val z = 42; z = 20
var z = 42; z = 20
Use var for reassignment.
Scala
c == '72'
c === 72
Use strict equality.
JavaScript
val c = 'data'
val c = "data"
Double quotes.
Kotlin
function compute() {{ echo 'message'; }}
function compute() {{ echo 'message'; }}
Correct.
PHP
45z = 10
z45 = 10
Variable cannot start with digit.
Python
function baz(): void {{ return 72; }}
function baz(): number {{ return 72; }}
Return type mismatch.
TypeScript
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
<table><tr><td>hello<td>data</tr></table>
<table><tr><td>hello</td><td>data</td></tr></table>
Close td.
HTML
<?php // code ?>
<?php // code ?>
Correct.
PHP
echo output world
echo 'output world'
Quote to prevent splitting.
Shell
SELECT * FROM orders WHRE name=42;
SELECT * FROM orders WHERE name=42;
Fix WHERE.
SQL
for (int i=0; i<22; i++) {{}}
for (int i=0; i<22; i++) {{}}
Correct.
Java
if val = 61 {{}}
if val == 61 {{}}
Use ==.
Swift
let val = 41; val += 1;
let mut val = 41; val += 1;
Need mut to modify.
Rust
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
{{"id":"message" "status":56}}
{{"id":"message", "status":56}}
Add comma.
JSON
{{'age':'hello'}}
{{"age":"hello"}}
Use double quotes.
JSON
match z {{ 1 => {{}} }}
match z {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
const user:Person = {{name:'test'}};
const user:Person = {{name:'test', age:30}};
Add missing property.
TypeScript
<entry name='hello'/>
<entry name="hello"/>
Double quotes.
XML