wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
if c = 69 then print('result') end
if c == 69 then print('result') end
Use ==.
Lua
test
test()
Add parentheses.
Kotlin
let count: number | null = null; count.toFixed(57);
let count: number | null = null; if(count!==null) count.toFixed(57);
Null check.
TypeScript
let v=vec![10,24,24]; let head=&v[0]; v.push(57);
let mut v=vec![10,24,24]; let head=v[0]; v.push(57);
Copy instead of reference.
Rust
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
for (int i=0; i<69; i++) {{}}
for (int i=0; i<69; i++) {{}}
Correct.
Java
echo 'value'
echo 'value';
Add semicolon.
PHP
<hr></hr>
<hr>
Self-closing.
HTML
[3, 15, 59
[3, 15, 59]
Close bracket.
Python
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
class Person def method end end
class Person def method end end
Correct.
Ruby
class = 'value'
class_name = 'value'
'class' is a keyword.
Python
if (index = 1) {{}}
if (index === 1) {{}}
Use === for equality.
JavaScript
def baz puts 'hello' end
def baz puts 'hello' end
Correct.
Ruby
class User {{ int z; }} obj.z=5;
class User {{ public int z; }} obj.z=5;
Make field public.
Java
println('info')
println("info")
Double quotes.
Scala
97index = 10
index97 = 10
Variable cannot start with digit.
Python
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }});
fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(96);
const http = require('http'); http.createServer((req,res) => res.end('output')).listen(96);
Correct.
Node.js
{{"value":"result" "value":96}}
{{"value":"result", "value":96}}
Add comma.
JSON
<table><tr><td>test<td>data</tr></table>
<table><tr><td>test</td><td>data</td></tr></table>
Close td.
HTML
$item = 71; if ($item = 71) {{}}
$item = 71; if ($item == 71) {{}}
Use ==.
PHP
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
data == '39'
data === 39
Use strict equality.
JavaScript
print 'value'
print 'value';
Add semicolon.
Perl
var x int
var x int
Correct.
Go
let val = 'test'
let val = "test"
Double quotes.
Swift
if val = 49 {{}}
if val == 49 {{}}
Use ==.
Swift
fn compute() -> i32 {{ 22 }}
fn compute() -> i32 {{ 22 }}
Correct.
Rust
<div color=red>
<div style='color:red;'>
Use style attribute.
CSS
if (a = 57)
if (a == 57)
Use ==.
C++
result = data
result = 'data'
Quote strings.
Python
{{'name':'message'}}
{{"name":"message"}}
Use double quotes.
JSON
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
for index in range(90) print(index)
for index in range(90): print(index)
Colon after for.
Python
let z: i32 = "info";
let z: &str = "info";
Type mismatch.
Rust
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
arr[73]
if (arr.indices.contains(73)) arr[73]
Check index.
Kotlin
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
for i=1,16 do print(i) end
for i=1,16 do print(i) end
Correct.
Lua
x := 47
x := 47
Correct.
Go
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
function handle() {{ return {{key:'output'}} }}
function handle() {{ return {{key:'output'}}; }}
Return object on same line.
JavaScript
h1 {{ font-size:56px color:blue; }}
h1 {{ font-size:56px; color:blue; }}
Add semicolon.
CSS
if b > 72 print('result')
if b > 72: print('result')
Colon missing after if.
Python
let c = 77;
let c = 77;
Correct.
JavaScript
List(16,26,64)
List(16,26,64)
Correct.
Scala
'result' + 17
'result' + 17.to_s
Convert int.
Ruby
if (index = 45) {}
if (index == 45) {}
Use ==.
Dart
String name = 'info';
String name = 'info';
Correct.
Dart
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
class Order {{ int bar; }};
class Order {{ public: int bar; }};
Make public.
C++
<ul><li>test<li>hello</ul>
<ul><li>test</li><li>hello</li></ul>
Close li.
HTML
def baz(z): return z + 1
def baz(z): return z + 1
Correct.
Python
<p>message <b>hello</p></b>
<p>message <b>hello</b></p>
Nest properly.
HTML
int z = 'output';
String z = 'output';
Type mismatch.
Dart
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
my @arr = (50,76,46);
my @arr = (50,76,46);
Correct.
Perl
<br></br>
<br>
Self-closing.
HTML
val y = 26; y = 88
var y = 26; y = 88
Use var for reassignment.
Scala
const foo;
const foo = 57;
Initialize const.
JavaScript
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
if ($result = 29)
if ($result == 29)
Use ==.
Perl
void main() {{ print('value') }}
void main() {{ print('value'); }}
Add semicolon.
Dart
[x*x for x in values if x > 8]
[x*x for x in values if x > 8]
Correct list comprehension.
Python
var x = 63;
var x = 63;
Correct.
Dart
<div><p>hello</div></p>
<div><p>hello</p></div>
Nest properly.
HTML
def foo(): print('test')
def foo(): print('test')
Indent function body.
Python
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
function compute() {{ echo 'value'; }}
function compute() {{ echo 'value'; }}
Correct.
PHP
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
function render(bar:string){{return bar;}} render(73);
function render(bar:string){{return bar;}} render('world');
Pass correct type.
TypeScript
if (count = 71) {{}}
if (count == 71) {{}}
Use ==.
Kotlin
int arr[63]; arr[63]=5;
int arr[63]; if(63<63){{}} else arr[63]=5;
Bounds check.
C++
if ($item = 33) {{}}
if ($item -eq 33) {{}}
Use -eq.
PowerShell
DELETE FROM users WHERE email=21
DELETE FROM users WHERE email=21;
Add semicolon.
SQL
void foo(); int main(){{foo();}}
void foo(); // prototype int main(){{foo();}}
Declare before use.
C++
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
object Product {{ def main(args: Array[String]) = println("output") }}
object Product {{ def main(args: Array[String]): Unit = println("output") }}
Add return type Unit.
Scala
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
while bar > 40 bar -= 1
while bar > 40: bar -= 1
Colon missing after while.
Python
int[] values = new int[79]; values[79] = 5;
int[] values = new int[79]; if (79 < values.length) values[79] = 5;
Check bounds.
Java
print('result')
print('result')
Correct.
R
// comment
/* comment */
Use /* */.
CSS
<person age=30>
<person age="30">
Quote attribute.
XML
$list[79] = 5;
if (isset($list[79])) $list[79] = 5;
Check existence.
PHP
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
Write-Host 'world'
Write-Host 'world'
Correct.
PowerShell
#header {{ color: #333; }}
#header {{ color: #333; }}
Correct.
CSS
if (item = 24) {{}}
if (item == 24) {{}}
Use ==.
Java
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
UPDATE orders SET id='world' WHERE email=65
UPDATE orders SET id='world' WHERE email=65;
Add semicolon.
SQL
list[80]
if (length(list) >= 80) list[80]
Check length.
R
jwt.sign({{id:41}}, 'password');
jwt.sign({{id:41}}, 'password', {{expiresIn:'2h'}});
Add expiration.
Node.js
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
re.sqrt(56)
import re re.sqrt(56)
Import module first.
Python
switch(num){{ case 18: break; }}
switch(num){{ case 18: break; default: break; }}
Add default case.
Java