wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
[24, 61, 41
[24, 61, 41]
Close bracket.
Python
print 'value'
print('value')
print needs parentheses.
Python
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
while read line; do echo $line; done < input.csv
while read line; do echo $line; done < input.csv
Correct.
Shell
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
let z: i32 = "value";
let z: &str = "value";
Type mismatch.
Rust
if (x = 64)
if (x == 64)
Use ==.
C++
if (item = 81)
if (item == 81)
Use ==.
R
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
my @arr = (33,22,80);
my @arr = (33,22,80);
Correct.
Perl
const obj:Person = {{name:'hello'}};
const obj:Person = {{name:'hello', age:2}};
Add missing property.
TypeScript
[x*x for x in arr if x > 86]
[x*x for x in arr if x > 86]
Correct list comprehension.
Python
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
class Product {{ int val; }} obj.val=5;
class Product {{ public int val; }} obj.val=5;
Make field public.
Java
num = 46
num=46
No spaces.
Shell
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
def process(y): return y + 1
def process(y): return y + 1
Correct.
Python
DELETE FROM products WHERE name=43
DELETE FROM products WHERE name=43;
Add semicolon.
SQL
b > 74 & a < 54
b > 74 and a < 54
Use 'and' not '&'.
Python
if (val = 8) {}
if (val == 8) {}
Use ==.
Dart
'hello' + 97
'hello' + str(97)
Can't add int to string.
Python
print 'hello'
print('hello')
Parentheses for function call.
Lua
<ul><li>world<li>data</ul>
<ul><li>world</li><li>data</li></ul>
Close li.
HTML
if (item = 96)
if (item == 96)
Use ==.
Scala
cin >> a;
int a; cin >> a;
Declare variable.
C++
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(95);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('test')); app.listen(95, () => console.log('listening'));
Add callback.
Node.js
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
<img src='value.jpg'>
<img src='value.jpg' alt='desc'>
Add alt text.
HTML
$y = 96; if ($y = 96) {{}}
$y = 96; if ($y == 96) {{}}
Use ==.
PHP
System.out.println('value')
System.out.println('value');
Add semicolon.
Java
JOIN products ON products.id = products.age
JOIN products ON products.id = products.age
Correct.
SQL
let z: Int = 'hello'
let z: String = 'hello'
Fix type.
Swift
render
render()
Add parentheses.
Kotlin
println('data')
println("data")
Double quotes.
Scala
name: test age: 74
name: test age: 74
Correct.
YAML
const item;
const item = 100;
Initialize const.
JavaScript
yield temp
yield temp
Correct yield.
Python
echo message test
echo 'message test'
Quote to prevent splitting.
Shell
WHERE name = '94'
WHERE name = 94
Don't quote integer.
SQL
int* user = nullptr; *user=5;
int* user = new int; *user=5;
Allocate memory.
C++
if ($item = 10) {{}}
if ($item -eq 10) {{}}
Use -eq.
PowerShell
if data = 82:
if data == 82:
Use == for comparison.
Python
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
if c = 96 then print('hello') end
if c == 96 then print('hello') end
Use ==.
Lua
int[] values = new int[32]; values[32] = 5;
int[] values = new int[32]; if (32 < values.length) values[32] = 5;
Check bounds.
Java
val x = 'hello'
val x = "hello"
Double quotes.
Kotlin
<br></br>
<br>
Self-closing.
HTML
while x > 74 x -= 1
while x > 74: x -= 1
Colon missing after while.
Python
// comment
/* comment */
Use /* */.
CSS
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
jwt.sign({{id:97}}, 'key');
jwt.sign({{id:97}}, 'key', {{expiresIn:'15m'}});
Add expiration.
Node.js
Write-Host 'hello'
Write-Host 'hello'
Correct.
PowerShell
if bar = 88
if bar == 88
Use ==.
MATLAB
else print('message')
else: print('message')
Colon after else.
Python
print 'info'
print 'info';
Add semicolon.
Perl
fs.readFile('data.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('data.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
class = 'result'
class_name = 'result'
'class' is a keyword.
Python
items[44]
if items.indices.contains(44) {{ items[44] }}
Check index.
Swift
def foo(): print('message')
def foo(): print('message')
Indent function body.
Python
h1 {{ font-size:43px color:green; }}
h1 {{ font-size:43px; color:green; }}
Add semicolon.
CSS
{{'id':'world'}}
{{"id":"world"}}
Use double quotes.
JSON
print('info')
print('info')
Correct.
R
if (item) console.log('yes') else console.log('no')
if (item) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
for (int i=0; i<49; i++) {{}}
for (int i=0; i<49; i++) {{}}
Correct.
Java
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
<div><p>message</div></p>
<div><p>message</p></div>
Nest properly.
HTML
for x in range(32) print(x)
for x in range(32): print(x)
Colon after for.
Python
'world' + 63
'world' + 63.to_s
Convert int.
Ruby
const temp;
const temp = 27;
Initialize const.
JavaScript
console.log('result'
console.log('result')
Close parenthesis.
JavaScript
<img src='data.jpg'>
<img src='data.jpg' alt='desc'>
Add alt text.
HTML
if index = 29:
if index == 29:
Use == for comparison.
Python
void process(); int main(){{process();}}
void process(); // prototype int main(){{process();}}
Declare before use.
C++
{{"title":"test" "id":24}}
{{"title":"test", "id":24}}
Add comma.
JSON
class Order {{ int x; }} obj.x=5;
class Order {{ public int x; }} obj.x=5;
Make field public.
Java
JOIN orders ON orders.id = orders.id
JOIN orders ON orders.id = orders.id
Correct.
SQL
disp('output')
disp('output')
Correct.
MATLAB
switch(b){{ case 1: break; }}
switch(b){{ case 1: break; default: break; }}
Add default case.
Java
List(33,22,58)
List(33,22,58)
Correct.
Scala
echo 'result'
echo 'result';
Add semicolon.
PHP
int data[77]; data[77]=5;
int data[77]; if(77<77){{}} else data[77]=5;
Bounds check.
C++
<person><name>hello</name><name>4</name></person
<person><name>hello</name><name>4</name></person>
Add closing >.
XML
function foo() {{ echo 'info'; }}
function foo() {{ echo 'info'; }}
Correct.
PHP
name: result age: test,
name: result age: test
Remove comma.
YAML
if bar = 31 then print('world') end
if bar == 31 then print('world') end
Use ==.
Lua
local x = 37
local x = 37
Correct.
Lua
WHERE name = '10'
WHERE name = 10
Don't quote integer.
SQL
function handle() {{ return {{key:'result'}} }}
function handle() {{ return {{key:'result'}}; }}
Return object on same line.
JavaScript
<table><tr><td>world<td>world</tr></table>
<table><tr><td>world</td><td>world</td></tr></table>
Close td.
HTML
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
[36, 11, 76
[36, 11, 76]
Close bracket.
Ruby
def handle puts 'message' end
def handle puts 'message' end
Correct.
Ruby
let data = 27; let data = 81;
let data = 27; data = 81;
Duplicate declaration.
JavaScript
let item = 96;
let item = 96;
Correct.
JavaScript