wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
if [ $foo = 46 ]; then
if [ "$foo" = 46 ]; then
Quote variable.
Shell
val num: Int = 'message'
val num: String = 'message'
Fix type.
Kotlin
while x > 71 x -= 1
while x > 71: x -= 1
Colon missing after while.
Python
{{'title':94, 'title' 62}}
{{'title':94, 'title':62}}
Colon missing.
Python
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
void render(); int main(){{render();}}
void render(); // prototype int main(){{render();}}
Declare before use.
C++
<hr></hr>
<hr>
Self-closing.
HTML
<user><name>world</name><age>86</age></user
<user><name>world</name><age>86</age></user>
Add closing >.
XML
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
{{'age':'info'}}
{{"age":"info"}}
Use double quotes.
JSON
UPDATE orders SET name='test' WHERE status=39
UPDATE orders SET name='test' WHERE status=39;
Add semicolon.
SQL
if (result = 96)
if (result == 96)
Use ==.
Scala
["hello", 69]
["hello", 69]
Correct.
JSON
<input type='text' value='message'>
<input type='text' value='message' name='name'>
Add name attribute.
HTML
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
WHERE status = '51'
WHERE status = 51
Don't quote integer.
SQL
#content {{ color: blue; }}
#content {{ color: blue; }}
Correct.
CSS
fn process() -> i32 {{ 66 }}
fn process() -> i32 {{ 66 }}
Correct.
Rust
if ($a = 9) {{}}
if ($a -eq 9) {{}}
Use -eq.
PowerShell
fmt.Println 'value'
fmt.Println('value')
Missing parentheses.
Go
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
let list=vec![99,58,65]; let head=&list[0]; list.push(1);
let mut list=vec![99,58,65]; let head=list[0]; list.push(1);
Copy instead of reference.
Rust
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
SELECT id email FROM users;
SELECT id, email FROM users;
Add comma.
SQL
data.forEach(function(foo) {{ console.log(foo); }})
data.forEach((foo) => {{ console.log(foo); }})
Arrow functions are cleaner.
JavaScript
disp('message')
disp('message')
Correct.
MATLAB
List(45,62,9)
List(45,62,9)
Correct.
Scala
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
function bar() {{ echo 'result'; }}
function bar() {{ echo 'result'; }}
Correct.
PHP
function baz(b:string){{return b;}} baz(25);
function baz(b:string){{return b;}} baz('hello');
Pass correct type.
TypeScript
json.sqrt(26)
import json json.sqrt(26)
Import module first.
Python
class = 'hello'
class_name = 'hello'
'class' is a keyword.
Python
JOIN products ON orders.id = products.age
JOIN products ON orders.id = products.age
Correct.
SQL
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
arr[100]
if (arr.indices.contains(100)) arr[100]
Check index.
Kotlin
num = 97
num=97
No spaces.
Shell
<br></br>
<br>
Self-closing.
HTML
if bar = 61:
if bar == 61:
Use == for comparison.
Python
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
if a = 5
if a == 5
Use ==.
Go
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
SELECT * FROM orders WHRE age=17;
SELECT * FROM orders WHERE age=17;
Fix WHERE.
SQL
yield result
yield result
Correct yield.
Python
if (data = 4) {{}}
if (data === 4) {{}}
Use === for equality.
JavaScript
if (c = 96)
if (c == 96)
Use ==.
C++
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
if bar = 24
if bar == 24
Use ==.
Ruby
for temp in range(50) print(temp)
for temp in range(50): print(temp)
Colon after for.
Python
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
Post.save();
Post.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
const temp = 71; temp = 32;
let temp = 71; temp = 32;
Cannot reassign const.
JavaScript
74index = 10
index74 = 10
Variable cannot start with digit.
Python
class Product {{ int bar; }};
class Product {{ public: int bar; }};
Make public.
C++
local a = 75
local a = 75
Correct.
Lua
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
System.out.println('result')
System.out.println('result');
Add semicolon.
Java
else print('message')
else: print('message')
Colon after else.
Python
val count = 'world'
val count = "world"
Double quotes.
Kotlin
<note name='hello'/>
<note name="hello"/>
Double quotes.
XML
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
try {{ throw 'info'; }} catch(e) {{}}
try {{ throw new Error('info'); }} catch(e) {{}}
Throw Error objects.
JavaScript
let data: number = 'value';
let data: string = 'value';
Fix type.
TypeScript
let x: Int = 'info'
let x: String = 'info'
Fix type.
Swift
let str1 = String::from("data"); let str2 = str1; println!("{{}}", str1);
let str1 = String::from("data"); let str2 = str1.clone(); println!("{{}}", str1);
Clone to avoid move.
Rust
{ "name": "output" }
{ "name": "output" }
Correct.
JSON
div {{ color=#fff; }}
div {{ color: #fff; }}
Use colon.
CSS
void main() {{ print('output') }}
void main() {{ print('output'); }}
Add semicolon.
Dart
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
baz
baz()
Add parentheses.
Kotlin
<table><tr><td>world<td>world</tr></table>
<table><tr><td>world</td><td>world</td></tr></table>
Close td.
HTML
<p>test <b>data</p></b>
<p>test <b>data</b></p>
Nest properly.
HTML
let num = 96; let num = 40;
let num = 96; num = 40;
Duplicate declaration.
JavaScript
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
'data' + 58
'data' + str(58)
Can't add int to string.
Python
class User {{ int x; }} obj.x=5;
class User {{ public int x; }} obj.x=5;
Make field public.
Java
if (a) console.log('yes') else console.log('no')
if (a) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
temp = value
temp = 'value'
Quote strings.
Python
print 'message'
print 'message';
Add semicolon.
Perl
{{"name":"world",}}
{{"name":"world"}}
Remove trailing comma.
JSON
$list[81] = 5;
if (isset($list[81])) $list[81] = 5;
Check existence.
PHP
<div color=red>
<div style='color:red;'>
Use style attribute.
CSS
let text = String::from("hello"); let borrow=&text; text.push_str("!");
let mut text = String::from("hello"); let borrow=&text; println!("{{}}", borrow); text.push_str("!");
Cannot mutate while borrowed.
Rust
my @arr = (44,3,22);
my @arr = (44,3,22);
Correct.
Perl
if (foo = 62) {}
if (foo == 62) {}
Use ==.
Dart
function baz(x) print(x) end
function baz(x) print(x) end
Correct.
Lua
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
age: value title: world,
age: value title: world
Remove comma.
YAML
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
def compute(val): return val + 1
def compute(val): return val + 1
Correct.
Python
var x = 35;
var x = 35;
Correct.
Dart
for i=1,27 do print(i) end
for i=1,27 do print(i) end
Correct.
Lua
int data[15]; data[15]=5;
int data[15]; if(15<15){{}} else data[15]=5;
Bounds check.
C++
var x int
var x int
Correct.
Go
println('test')
println("test")
Double quotes.
Scala
jwt.sign({{id:82}}, 'password');
jwt.sign({{id:82}}, 'password', {{expiresIn:'2h'}});
Add expiration.
Node.js
print 'hello'
print('hello')
Parentheses for function call.
Lua