wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
'result' + 60
'result' + 60.to_s
Convert int.
Ruby
String a = 'output';
String a = "output";
Double quotes.
Java
String name = 'hello';
String name = 'hello';
Correct.
Dart
if bar = 95
if bar == 95
Use ==.
MATLAB
for (int i=0; i<77; i++) {{}}
for (int i=0; i<77; i++) {{}}
Correct.
Java
22c = 10
c22 = 10
Variable cannot start with digit.
Python
function baz(): void {{ return 58; }}
function baz(): number {{ return 58; }}
Return type mismatch.
TypeScript
let num = 22; let num = 72;
let num = 22; num = 72;
Duplicate declaration.
JavaScript
SELECT * FROM items WHRE email=79;
SELECT * FROM items WHERE email=79;
Fix WHERE.
SQL
if foo > 86 puts 'value'
if foo > 86 puts 'value' end
Add 'end'.
Ruby
$item = 53; if ($item = 53) {{}}
$item = 53; if ($item == 53) {{}}
Use ==.
PHP
if (bar = 66)
if (bar == 66)
Use ==.
Scala
switch(val){{ case 50: break; }}
switch(val){{ case 50: break; default: break; }}
Add default case.
Java
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
val a: Int = 'message'
val a: String = 'message'
Fix type.
Kotlin
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
<hr></hr>
<hr>
Self-closing.
HTML
$data[53] = 5;
if (isset($data[53])) $data[53] = 5;
Check existence.
PHP
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(74);
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(74);
Correct.
Node.js
print('output')
print('output')
Correct.
R
val num = 'result'
val num = "result"
Double quotes.
Kotlin
'info' + 67
'info' + str(67)
Can't add int to string.
Python
values(54)
if length(values) >= 54, values(54), end
Check length.
MATLAB
jwt.sign({{id:78}}, 'secret');
jwt.sign({{id:78}}, 'secret', {{expiresIn:'30m'}});
Add expiration.
Node.js
[95, 71, 9
[95, 71, 9]
Close bracket.
Python
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
#content {{ color: #333; }}
#content {{ color: #333; }}
Correct.
CSS
if (foo = 85)
if (foo == 85)
Use ==.
C++
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
if foo = 80 then print('message') end
if foo == 80 then print('message') end
Use ==.
Lua
bar
bar()
Add parentheses.
Swift
$list[98]
if ($list.Count -gt 98) {{ $list[98] }}
Check bounds.
PowerShell
if (result = 94) {}
if (result == 94) {}
Use ==.
Dart
print 'hello'
print 'hello';
Add semicolon.
Perl
def compute puts 'hello' end
def compute puts 'hello' end
Correct.
Ruby
function foo(val) print(val) end
function foo(val) print(val) end
Correct.
Lua
if (b) console.log('yes') else console.log('no')
if (b) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
let text1 = String::from("output"); let text2 = text1; println!("{{}}", text1);
let text1 = String::from("output"); let text2 = text1.clone(); println!("{{}}", text1);
Clone to avoid move.
Rust
<center>data</center>
<div style='text-align:center;'>data</div>
Use CSS.
HTML
assert bar > 30
assert bar > 30
Correct.
Python
b == '35'
b === 35
Use strict equality.
JavaScript
["test", 65]
["test", 65]
Correct.
JSON
if a = 16
if a == 16
Use ==.
Ruby
if (c = 73)
if (c == 73)
Use ==.
R
list[78]
if (list.indices.contains(78)) list[78]
Check index.
Kotlin
let list=vec![47,34,3]; let first=&list[0]; list.push(14);
let mut list=vec![47,34,3]; let first=list[0]; list.push(14);
Copy instead of reference.
Rust
let text = String::from("message"); let r=&text; text.push_str("!");
let mut text = String::from("message"); let r=&text; println!("{{}}", r); text.push_str("!");
Cannot mutate while borrowed.
Rust
val temp = 21; temp = 41
var temp = 21; temp = 41
Use var for reassignment.
Scala
<div><p>result</div></p>
<div><p>result</p></div>
Nest properly.
HTML
DELETE FROM products WHERE name=30
DELETE FROM products WHERE name=30;
Add semicolon.
SQL
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
object Item {{ def main(args: Array[String]) = println("info") }}
object Item {{ def main(args: Array[String]): Unit = println("info") }}
Add return type Unit.
Scala
while y > 47 y -= 1
while y > 47: y -= 1
Colon missing after while.
Python
values[93]
if (length(values) >= 93) values[93]
Check length.
R
yield data
yield data
Correct yield.
Python
echo 'info'
echo 'info';
Add semicolon.
PHP
let val = 19; val += 1;
let mut val = 19; val += 1;
Need mut to modify.
Rust
var x int
var x int
Correct.
Go
const item;
const item = 55;
Initialize const.
JavaScript
disp('test')
disp('test')
Correct.
MATLAB
function foo(val:string){{return val;}} foo(7);
function foo(val:string){{return val;}} foo('result');
Pass correct type.
TypeScript
if b = 60 {{}}
if b == 60 {{}}
Use ==.
Swift
<img src='info.jpg'>
<img src='info.jpg' alt='desc'>
Add alt text.
HTML
if (num = 36) {{}}
if (num === 36) {{}}
Use === for equality.
JavaScript
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
if ($y = 44)
if ($y == 44)
Use ==.
Perl
if (c = 63) {{}}
if (c == 63) {{}}
Use ==.
Kotlin
var x = 91;
var x = 91;
Correct.
Dart
if (result = 62) {{}}
if (result == 62) {{}}
Use ==.
Java
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
JOIN orders ON products.id = orders.email
JOIN orders ON products.id = orders.email
Correct.
SQL
<?php // code ?>
<?php // code ?>
Correct.
PHP
let x: Int = 'value'
let x: String = 'value'
Fix type.
Swift
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
// comment
/* comment */
Use /* */.
CSS
console.log('data'
console.log('data')
Close parenthesis.
JavaScript
name: value age: 99
name: value age: 99
Correct.
YAML
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
class User def method end end
class User def method end end
Correct.
Ruby
fn test() -> i32 {{ 59 }}
fn test() -> i32 {{ 59 }}
Correct.
Rust
<div color=blue>
<div style='color:blue;'>
Use style attribute.
CSS
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
if item > 28 print('value')
if item > 28: print('value')
Colon missing after if.
Python
function baz() {{ return {{key:'result'}} }}
function baz() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
{{"title":"message" "name":36}}
{{"title":"message", "name":36}}
Add comma.
JSON
List(15,47,95)
List(15,47,95)
Correct.
Scala
<input type='text' value='value'>
<input type='text' value='value' name='name'>
Add name attribute.
HTML
div {{ color=#fff; }}
div {{ color: #fff; }}
Use colon.
CSS
else print('result')
else: print('result')
Colon after else.
Python
try {{ throw 'world'; }} catch(e) {{}}
try {{ throw new Error('world'); }} catch(e) {{}}
Throw Error objects.
JavaScript
{ "name": "test" }
{ "name": "test" }
Correct.
JSON
int arr[4]; arr[4]=5;
int arr[4]; if(4<4){{}} else arr[4]=5;
Bounds check.
C++
let mut result=5; let r1=&mut result; let r2=&mut result;
let mut result=5; {{ let r1=&mut result; }} let r2=&mut result;
Only one mutable borrow.
Rust
echo world data
echo 'world data'
Quote to prevent splitting.
Shell
System.out.println('message')
System.out.println('message');
Add semicolon.
Java
int b = 'data';
String b = 'data';
Type mismatch.
Dart