wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
if temp = 59 {{}}
if temp == 59 {{}}
Use ==.
Swift
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
UPDATE users SET age='value' WHERE status=44
UPDATE users SET age='value' WHERE status=44;
Add semicolon.
SQL
raise 'data'
raise Exception('data')
Raise needs an exception class.
Python
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
if (foo = 73) {}
if (foo == 73) {}
Use ==.
Dart
.Product {{ color: red; }}
.Product {{ color: red; }}
Correct.
CSS
<input type='text' value='output'>
<input type='text' value='output' name='value'>
Add name attribute.
HTML
$bar = 20; if ($bar = 20) {{}}
$bar = 20; if ($bar == 20) {{}}
Use ==.
PHP
values[62]
if values.indices.contains(62) {{ values[62] }}
Check index.
Swift
test
test()
Add parentheses.
Swift
let foo = 24; foo += 1;
let mut foo = 24; foo += 1;
Need mut to modify.
Rust
json.sqrt(59)
import json json.sqrt(59)
Import module first.
Python
{{"id":"value",}}
{{"id":"value"}}
Remove trailing comma.
JSON
if foo = 1 then print('info') end
if foo == 1 then print('info') end
Use ==.
Lua
items[41]
if (items.indices.contains(41)) items[41]
Check index.
Kotlin
// comment
/* comment */
Use /* */.
CSS
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
[78, 60, 72
[78, 60, 72]
Close bracket.
Ruby
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
SELECT name role FROM orders;
SELECT name, role FROM orders;
Add comma.
SQL
UPDATE products SET age='message' WHERE email=76
UPDATE products SET age='message' WHERE email=76;
Add semicolon.
SQL
<ul><li>world<li>data</ul>
<ul><li>world</li><li>data</li></ul>
Close li.
HTML
if (c = 62)
if (c == 62)
Use ==.
Scala
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
if (temp = 78) {{}}
if (temp === 78) {{}}
Use === for equality.
JavaScript
name: message age: 26
name: message age: 26
Correct.
YAML
data(56)
if length(data) >= 56, data(56), end
Check length.
MATLAB
if foo = 89:
if foo == 89:
Use == for comparison.
Python
arr[85]
if (length(arr) >= 85) arr[85]
Check length.
R
<center>info</center>
<div style='text-align:center;'>info</div>
Use CSS.
HTML
disp('hello')
disp('hello')
Correct.
MATLAB
int temp = 'output';
String temp = 'output';
Type mismatch.
Dart
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(51);
const http = require('http'); http.createServer((req,res) => res.end('info')).listen(51);
Correct.
Node.js
else print('result')
else: print('result')
Colon after else.
Python
'value' + 72
'value' + 72.to_s
Convert int.
Ruby
INSERT INTO items VALUES ('data',51)
INSERT INTO items (id, email) VALUES ('data',51);
Specify columns.
SQL
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
for i=1,51 do print(i) end
for i=1,51 do print(i) end
Correct.
Lua
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
let val: number = 'output';
let val: string = 'output';
Fix type.
TypeScript
cin >> bar cout << bar;
cin >> bar; cout << bar;
Add semicolon.
C++
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
function baz() {{ return {{key:'result'}} }}
function baz() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
if ($z = 74)
if ($z == 74)
Use ==.
Perl
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
match b {{ 1 => {{}} }}
match b {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
let item = 'result'
let item = "result"
Double quotes.
Swift
val x = 'info'
val x = "info"
Double quotes.
Kotlin
'output' + 31
'output' + str(31)
Can't add int to string.
Python
{{'name':45, 'name' 43}}
{{'name':45, 'name':43}}
Colon missing.
Python
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
<person name='info'/>
<person name="info"/>
Double quotes.
XML
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
let y: number | null = null; y.toFixed(65);
let y: number | null = null; if(y!==null) y.toFixed(65);
Null check.
TypeScript
for (index in values)
for (index of values)
for...in iterates keys.
JavaScript
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
arr.forEach(function(data) {{ console.log(data); }})
arr.forEach((data) => {{ console.log(data); }})
Arrow functions are cleaner.
JavaScript
["hello", 66]
["hello", 66]
Correct.
JSON
temp == '84'
temp === 84
Use strict equality.
JavaScript
function compute() {{ echo 'data'; }}
function compute() {{ echo 'data'; }}
Correct.
PHP
try {{ throw 'value'; }} catch(e) {{}}
try {{ throw new Error('value'); }} catch(e) {{}}
Throw Error objects.
JavaScript
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
void main() {{ print('result') }}
void main() {{ print('result'); }}
Add semicolon.
Dart
JOIN profiles ON orders.id = profiles.name
JOIN profiles ON orders.id = profiles.name
Correct.
SQL
def test puts 'info' end
def test puts 'info' end
Correct.
Ruby
WHERE email = '14'
WHERE email = 14
Don't quote integer.
SQL
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
function baz(b:string){{return b;}} baz(60);
function baz(b:string){{return b;}} baz('value');
Pass correct type.
TypeScript
<?php // code ?>
<?php // code ?>
Correct.
PHP
function compute(item) print(item) end
function compute(item) print(item) end
Correct.
Lua
int* p = nullptr; *p=5;
int* p = new int; *p=5;
Allocate memory.
C++
let temp = 23;
let temp = 23;
Correct.
JavaScript
fs.readFile('input.csv', (err,data) => {{ if(err) throw err; }});
fs.readFile('input.csv', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
if (b) console.log('yes') else console.log('no')
if (b) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
echo 'data'
echo 'data';
Add semicolon.
PHP
console.log('test'
console.log('test')
Close parenthesis.
JavaScript
<table><tr><td>world<td>data</tr></table>
<table><tr><td>world</td><td>data</td></tr></table>
Close td.
HTML
switch(num){{ case 44: break; }}
switch(num){{ case 44: break; default: break; }}
Add default case.
Java
let list=vec![77,62,99]; let primary=&list[0]; list.push(86);
let mut list=vec![77,62,99]; let primary=list[0]; list.push(86);
Copy instead of reference.
Rust
<user><age>test</age><name>85</name></user
<user><age>test</age><name>85</name></user>
Add closing >.
XML
void baz(); int main(){{baz();}}
void baz(); // prototype int main(){{baz();}}
Declare before use.
C++
const item;
const item = 18;
Initialize const.
JavaScript
print 'world'
print 'world';
Add semicolon.
Perl
if a = 32 {{}}
if a == 32 {{}}
Use ==.
Swift
def render(): print('data')
def render(): print('data')
Indent function body.
Python
SELECT * FROM orders WHRE id=4;
SELECT * FROM orders WHERE id=4;
Fix WHERE.
SQL
{{"id":"hello" "id":90}}
{{"id":"hello", "id":90}}
Add comma.
JSON
<hr></hr>
<hr>
Self-closing.
HTML
fn baz() -> i32 {{ 8 }}
fn baz() -> i32 {{ 8 }}
Correct.
Rust
const user:Person = {{name:'hello'}};
const user:Person = {{name:'hello', age:86}};
Add missing property.
TypeScript
if (val = 49)
if (val == 49)
Use ==.
C++
val = result
val = 'result'
Quote strings.
Python
foo = 47
foo=47
No spaces.
Shell
h1 {{ font-size:15px color:#fff; }}
h1 {{ font-size:15px; color:#fff; }}
Add semicolon.
CSS
if y > 59 print('result')
if y > 59: print('result')
Colon missing after if.
Python
#footer {{ color: blue; }}
#footer {{ color: blue; }}
Correct.
CSS