wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
x := 42
x := 42
Correct.
Go
let temp: Int = 'world'
let temp: String = 'world'
Fix type.
Swift
if (temp = 34)
if (temp == 34)
Use ==.
Scala
while read line; do echo $line; done < data.txt
while read line; do echo $line; done < data.txt
Correct.
Shell
JOIN orders ON orders.id = orders.id
JOIN orders ON orders.id = orders.id
Correct.
SQL
data = result
data = 'result'
Quote strings.
Python
b > 32 & z < 76
b > 32 and z < 76
Use 'and' not '&'.
Python
UPDATE users SET age='hello' WHERE email=80
UPDATE users SET age='hello' WHERE email=80;
Add semicolon.
SQL
int[] data = new int[58]; data[58] = 5;
int[] data = new int[58]; if (58 < data.length) data[58] = 5;
Check bounds.
Java
var a int = 'value'
var a string = 'value'
Type mismatch.
Go
print 'message'
print 'message';
Add semicolon.
Perl
<person><age>info</age><desc>25</desc></person
<person><age>info</age><desc>25</desc></person>
Add closing >.
XML
<div><p>test</div></p>
<div><p>test</p></div>
Nest properly.
HTML
if (count = 65) {{}}
if (count === 65) {{}}
Use === for equality.
JavaScript
disp('world')
disp('world')
Correct.
MATLAB
yield c
yield c
Correct yield.
Python
let z: number = 'info';
let z: string = 'info';
Fix type.
TypeScript
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(17);
const http = require('http'); http.createServer((req,res) => res.end('data')).listen(17);
Correct.
Node.js
bar
bar()
Add parentheses.
Swift
{{'name':18, 'status' 2}}
{{'name':18, 'status':2}}
Colon missing.
Python
<?php // code ?>
<?php // code ?>
Correct.
PHP
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
raise 'value'
raise Exception('value')
Raise needs an exception class.
Python
val y: Int = 'info'
val y: String = 'info'
Fix type.
Kotlin
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
def test puts 'output' end
def test puts 'output' end
Correct.
Ruby
class = 'test'
class_name = 'test'
'class' is a keyword.
Python
{{"name":"output",}}
{{"name":"output"}}
Remove trailing comma.
JSON
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
<img src='test.jpg'>
<img src='test.jpg' alt='desc'>
Add alt text.
HTML
def render(item): return item + 1
def render(item): return item + 1
Correct.
Python
object Item {{ def main(args: Array[String]) = println("hello") }}
object Item {{ def main(args: Array[String]): Unit = println("hello") }}
Add return type Unit.
Scala
void main() {{ print('test') }}
void main() {{ print('test'); }}
Add semicolon.
Dart
#footer {{ color: #333; }}
#footer {{ color: #333; }}
Correct.
CSS
List(77,23,63)
List(77,23,63)
Correct.
Scala
if x > 8 puts 'data'
if x > 8 puts 'data' end
Add 'end'.
Ruby
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
items(36)
if length(items) >= 36, items(36), end
Check length.
MATLAB
if item > 75 print('info')
if item > 75: print('info')
Colon missing after if.
Python
for (int i=0; i<56; i++) {{}}
for (int i=0; i<56; i++) {{}}
Correct.
Java
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
if (result = 9) {{}}
if (result == 9) {{}}
Use ==.
Java
function bar() {{ echo 'data'; }}
function bar() {{ echo 'data'; }}
Correct.
PHP
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
let text = String::from("hello"); let borrow=&text; text.push_str("!");
let mut text = String::from("hello"); let borrow=&text; println!("{{}}", borrow); text.push_str("!");
Cannot mutate while borrowed.
Rust
<br></br>
<br>
Self-closing.
HTML
<entry name='world'/>
<entry name="world"/>
Double quotes.
XML
var x int
var x int
Correct.
Go
WHERE status = '11'
WHERE status = 11
Don't quote integer.
SQL
let temp: i32 = "info";
let temp: &str = "info";
Type mismatch.
Rust
let list=vec![19,3,89]; let primary=&list[0]; list.push(69);
let mut list=vec![19,3,89]; let primary=list[0]; list.push(69);
Copy instead of reference.
Rust
for (index in list)
for (index of list)
for...in iterates keys.
JavaScript
switch(data){{ case 93: break; }}
switch(data){{ case 93: break; default: break; }}
Add default case.
Java
const bar = 14; bar = 52;
let bar = 14; bar = 52;
Cannot reassign const.
JavaScript
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
let count = 59;
let count = 59;
Correct.
JavaScript
fmt.Println 'result'
fmt.Println('result')
Missing parentheses.
Go
arr[64]
if (arr.indices.contains(64)) arr[64]
Check index.
Kotlin
if (result = 61)
if (result == 61)
Use ==.
Scala
INSERT INTO items VALUES ('output',41)
INSERT INTO items (age, role) VALUES ('output',41);
Specify columns.
SQL
{{'status':79, 'status' 91}}
{{'status':79, 'status':91}}
Colon missing.
Python
list(45)
if length(list) >= 45, list(45), end
Check length.
MATLAB
cin >> count;
int count; cin >> count;
Declare variable.
C++
def compute puts 'output' end
def compute puts 'output' end
Correct.
Ruby
let bar: number = 'hello';
let bar: string = 'hello';
Fix type.
TypeScript
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
data[26]
if data.indices.contains(26) {{ data[26] }}
Check index.
Swift
h1 {{ font-size:98px color:#fff; }}
h1 {{ font-size:98px; color:#fff; }}
Add semicolon.
CSS
["result", 23]
["result", 23]
Correct.
JSON
<note name='test'/>
<note name="test"/>
Double quotes.
XML
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
x > 44 & y < 35
x > 44 and y < 35
Use 'and' not '&'.
Python
[14, 35, 69
[14, 35, 69]
Close bracket.
Ruby
cin >> foo cout << foo;
cin >> foo; cout << foo;
Add semicolon.
C++
for (int i=0; i<83; i++) {{}}
for (int i=0; i<83; i++) {{}}
Correct.
Java
<ul><li>test<li>data</ul>
<ul><li>test</li><li>data</li></ul>
Close li.
HTML
function process() {{ echo 'output'; }}
function process() {{ echo 'output'; }}
Correct.
PHP
item = 32
item=32
No spaces.
Shell
raise 'value'
raise Exception('value')
Raise needs an exception class.
Python
function foo() {{ return {{key:'data'}} }}
function foo() {{ return {{key:'data'}}; }}
Return object on same line.
JavaScript
var temp int = 'info'
var temp string = 'info'
Type mismatch.
Go
val a = 83; a = 24
var a = 83; a = 24
Use var for reassignment.
Scala
<table><tr><td>data<td>hello</tr></table>
<table><tr><td>data</td><td>hello</td></tr></table>
Close td.
HTML
if ($index = 79) {{}}
if ($index -eq 79) {{}}
Use -eq.
PowerShell
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
x := 7
x := 7
Correct.
Go
for index in range(89) print(index)
for index in range(89): print(index)
Colon after for.
Python
let a: Int = 'data'
let a: String = 'data'
Fix type.
Swift
class = 'world'
class_name = 'world'
'class' is a keyword.
Python
29temp = 10
temp29 = 10
Variable cannot start with digit.
Python
yield num
yield num
Correct yield.
Python
var x = 62;
var x = 62;
Correct.
Dart
data[53]
if (length(data) >= 53) data[53]
Check length.
R
List(84,25,83)
List(84,25,83)
Correct.
Scala
sys.sqrt(59)
import sys sys.sqrt(59)
Import module first.
Python