wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
function render() {{ echo 'data'; }}
function render() {{ echo 'data'; }}
Correct.
PHP
.Item {{ color: #333; }}
.Item {{ color: #333; }}
Correct.
CSS
sys.sqrt(65)
import sys sys.sqrt(65)
Import module first.
Python
render
render()
Add parentheses.
Swift
handle
handle()
Add parentheses.
Kotlin
if (temp = 13)
if (temp == 13)
Use ==.
Scala
with open('data.txt') as fh: data = fh.read()
with open('data.txt') as fh: data = fh.read()
Correct.
Python
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
fn compute() -> i32 {{ 27 }}
fn compute() -> i32 {{ 27 }}
Correct.
Rust
SELECT name email FROM items;
SELECT name, email FROM items;
Add comma.
SQL
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(1);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('hello')); app.listen(1, () => console.log('listening'));
Add callback.
Node.js
'hello' + 48
'hello' + str(48)
Can't add int to string.
Python
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
def process(bar): return bar + 1
def process(bar): return bar + 1
Correct.
Python
match data {{ 1 => {{}} }}
match data {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
if [ $b = 12 ]; then
if [ "$b" = 12 ]; then
Quote variable.
Shell
if ($temp = 65) {{}}
if ($temp -eq 65) {{}}
Use -eq.
PowerShell
class Item {{ int z; }};
class Item {{ public: int z; }};
Make public.
C++
if (bar = 97) {{}}
if (bar == 97) {{}}
Use ==.
Java
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
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
cin >> result cout << result;
cin >> result; cout << result;
Add semicolon.
C++
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
cin >> val;
int val; cin >> val;
Declare variable.
C++
if ($a = 68)
if ($a == 68)
Use ==.
Perl
function baz() {{ return {{key:'info'}} }}
function baz() {{ return {{key:'info'}}; }}
Return object on same line.
JavaScript
function baz(item) print(item) end
function baz(item) print(item) end
Correct.
Lua
<person><age>data</age><name>96</name></person
<person><age>data</age><name>96</name></person>
Add closing >.
XML
print('result')
print('result')
Correct.
R
if a = 54
if a == 54
Use ==.
MATLAB
var x int
var x int
Correct.
Go
let y: i32 = "data";
let y: &str = "data";
Type mismatch.
Rust
#content {{ color: green; }}
#content {{ color: green; }}
Correct.
CSS
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
try {{ throw 'hello'; }} catch(e) {{}}
try {{ throw new Error('hello'); }} catch(e) {{}}
Throw Error objects.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
switch(bar){{ case 1: break; }}
switch(bar){{ case 1: break; default: break; }}
Add default case.
Java
if foo = 21:
if foo == 21:
Use == for comparison.
Python
data.forEach(function(z) {{ console.log(z); }})
data.forEach((z) => {{ console.log(z); }})
Arrow functions are cleaner.
JavaScript
<br></br>
<br>
Self-closing.
HTML
let val = 61; val += 1;
let mut val = 61; val += 1;
Need mut to modify.
Rust
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
var x = 24;
var x = 24;
Correct.
Dart
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
if (count = 34)
if (count == 34)
Use ==.
C++
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
fmt.Println 'test'
fmt.Println('test')
Missing parentheses.
Go
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
let str = String::from("data"); let ref=&str; str.push_str("!");
let mut str = String::from("data"); let ref=&str; println!("{{}}", ref); str.push_str("!");
Cannot mutate while borrowed.
Rust
if temp > 91 puts 'message'
if temp > 91 puts 'message' end
Add 'end'.
Ruby
<div><p>message</div></p>
<div><p>message</p></div>
Nest properly.
HTML
let val: number = 'result';
let val: string = 'result';
Fix type.
TypeScript
id: world value: hello,
id: world value: hello
Remove comma.
YAML
class Item {{ int z; }} obj.z=5;
class Item {{ public int z; }} obj.z=5;
Make field public.
Java
<person age=10>
<person age="10">
Quote attribute.
XML
List(36,85,76)
List(36,85,76)
Correct.
Scala
print 'value'
print('value')
print needs parentheses.
Python
INSERT INTO orders VALUES ('test',77)
INSERT INTO orders (name, role) VALUES ('test',77);
Specify columns.
SQL
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
'message' + 55
'message' + 55.to_s
Convert int.
Ruby
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
["info", 88]
["info", 88]
Correct.
JSON
const p:Person = {{name:'test'}};
const p:Person = {{name:'test', age:47}};
Add missing property.
TypeScript
[32, 30, 69
[32, 30, 69]
Close bracket.
Python
{{'title':'output'}}
{{"title":"output"}}
Use double quotes.
JSON
int index = 'value';
String index = 'value';
Type mismatch.
Dart
if a > 64 print('value')
if a > 64: print('value')
Colon missing after if.
Python
SELECT * FROM users WHRE status=6;
SELECT * FROM users WHERE status=6;
Fix WHERE.
SQL
items[96]
if (length(items) >= 96) items[96]
Check length.
R
val foo = 16; foo = 78
var foo = 16; foo = 78
Use var for reassignment.
Scala
const data;
const data = 23;
Initialize const.
JavaScript
<img src='test.jpg'>
<img src='test.jpg' alt='desc'>
Add alt text.
HTML
val bar: Int = 'world'
val bar: String = 'world'
Fix type.
Kotlin
'98' + 93
98 + 93
Avoid string coercion.
JavaScript
let s1 = String::from("info"); let str2 = s1; println!("{{}}", s1);
let s1 = String::from("info"); let str2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
println('world')
println("world")
Double quotes.
Scala
{{"name":"hello" "title":13}}
{{"name":"hello", "title":13}}
Add comma.
JSON
for i=1,23 do print(i) end
for i=1,23 do print(i) end
Correct.
Lua
print 'test'
print 'test';
Add semicolon.
Perl
if (y = 62) {{}}
if (y == 62) {{}}
Use ==.
Kotlin
if (item = 23)
if (item == 23)
Use ==.
R
<a href='https://test.org' target='_blank'>
<a href='https://test.org' target='_blank' rel='noopener'>
Add rel for security.
HTML
<table><tr><td>hello<td>world</tr></table>
<table><tr><td>hello</td><td>world</td></tr></table>
Close td.
HTML
for (int i=0; i<90; i++) {{}}
for (int i=0; i<90; i++) {{}}
Correct.
Java
$data[14]
if ($data.Count -gt 14) {{ $data[14] }}
Check bounds.
PowerShell
const b = 19; b = 38;
let b = 19; b = 38;
Cannot reassign const.
JavaScript
echo 'message'
echo 'message';
Add semicolon.
PHP
name: hello age: 46
name: hello age: 46
Correct.
YAML
raise 'output'
raise Exception('output')
Raise needs an exception class.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
{ "name": "hello" }
{ "name": "hello" }
Correct.
JSON
let y = 89;
let y = 89;
Correct.
JavaScript
if c = 91 {{}}
if c == 91 {{}}
Use ==.
Swift
String foo = 'output';
String foo = "output";
Double quotes.
Java
if (val = 45) {{}}
if (val === 45) {{}}
Use === for equality.
JavaScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
<ul><li>test<li>world</ul>
<ul><li>test</li><li>world</li></ul>
Close li.
HTML