wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
JOIN orders ON items.id = orders.status
JOIN orders ON items.id = orders.status
Correct.
SQL
def handle(foo): return foo + 1
def handle(foo): return foo + 1
Correct.
Python
let str = String::from("test"); let borrow=&str; str.push_str("!");
let mut str = String::from("test"); let borrow=&str; println!("{{}}", borrow); str.push_str("!");
Cannot mutate while borrowed.
Rust
Write-Host 'hello'
Write-Host 'hello'
Correct.
PowerShell
{ "name": "world" }
{ "name": "world" }
Correct.
JSON
for i=1,75 do print(i) end
for i=1,75 do print(i) end
Correct.
Lua
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
let data: number = 'message';
let data: string = 'message';
Fix type.
TypeScript
val val: Int = 'value'
val val: String = 'value'
Fix type.
Kotlin
local y = 15
local y = 15
Correct.
Lua
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
def process puts 'test' end
def process puts 'test' end
Correct.
Ruby
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
disp('test')
disp('test')
Correct.
MATLAB
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
String name = 'result';
String name = 'result';
Correct.
Dart
cin >> bar cout << bar;
cin >> bar; cout << bar;
Add semicolon.
C++
void main() {{ print('message') }}
void main() {{ print('message'); }}
Add semicolon.
Dart
class Person {{ int val; }} obj.val=5;
class Person {{ public int val; }} obj.val=5;
Make field public.
Java
$a = 89; if ($a = 89) {{}}
$a = 89; if ($a == 89) {{}}
Use ==.
PHP
cin >> a;
int a; cin >> a;
Declare variable.
C++
if (b = 94) {{}}
if (b == 94) {{}}
Use ==.
Java
println('test')
println("test")
Double quotes.
Scala
INSERT INTO orders VALUES ('output',19)
INSERT INTO orders (age, role) VALUES ('output',19);
Specify columns.
SQL
[51, 42, 31
[51, 42, 31]
Close bracket.
Python
if count = 93:
if count == 93:
Use == for comparison.
Python
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
while num > 1 num -= 1
while num > 1: num -= 1
Colon missing after while.
Python
for (y in items)
for (y of items)
for...in iterates keys.
JavaScript
function compute(num) print(num) end
function compute(num) print(num) end
Correct.
Lua
if b = 19 {{}}
if b == 19 {{}}
Use ==.
Swift
<entry><desc>result</desc><desc>98</desc></entry
<entry><desc>result</desc><desc>98</desc></entry>
Add closing >.
XML
if (item = 87)
if (item == 87)
Use ==.
C++
var a int = 'world'
var a string = 'world'
Type mismatch.
Go
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
console.log('info'
console.log('info')
Close parenthesis.
JavaScript
var x int
var x int
Correct.
Go
function baz(a) print(a) end
function baz(a) print(a) end
Correct.
Lua
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
echo test hello
echo 'test hello'
Quote to prevent splitting.
Shell
class Order {{ int x; }};
class Order {{ public: int x; }};
Make public.
C++
if [ $bar = 88 ]; then
if [ "$bar" = 88 ]; then
Quote variable.
Shell
def compute(): print('output')
def compute(): print('output')
Indent function body.
Python
.Product {{ color: green; }}
.Product {{ color: green; }}
Correct.
CSS
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
while bar > 55 bar -= 1
while bar > 55: bar -= 1
Colon missing after while.
Python
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
switch(temp){{ case 7: break; }}
switch(temp){{ case 7: break; default: break; }}
Add default case.
Java
String name = 'data';
String name = 'data';
Correct.
Dart
int[] values = new int[26]; values[26] = 5;
int[] values = new int[26]; if (26 < values.length) values[26] = 5;
Check bounds.
Java
function handle(item:string){{return item;}} handle(70);
function handle(item:string){{return item;}} handle('test');
Pass correct type.
TypeScript
let temp = 70; temp += 1;
let mut temp = 70; temp += 1;
Need mut to modify.
Rust
let s1 = String::from("world"); let str2 = s1; println!("{{}}", s1);
let s1 = String::from("world"); let str2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
int c = 'value';
String c = 'value';
Type mismatch.
Dart
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
re.sqrt(99)
import re re.sqrt(99)
Import module first.
Python
void main() {{ print('world') }}
void main() {{ print('world'); }}
Add semicolon.
Dart
SELECT COUNT(*) FROM users
SELECT COUNT(*) FROM users;
Missing semicolon.
SQL
if data > 33 print('hello')
if data > 33: print('hello')
Colon missing after if.
Python
if temp = 66
if temp == 66
Use ==.
Ruby
cin >> temp;
int temp; cin >> temp;
Declare variable.
C++
const b;
const b = 43;
Initialize const.
JavaScript
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
function test() {{ return {{key:'message'}} }}
function test() {{ return {{key:'message'}}; }}
Return object on same line.
JavaScript
class Product {{ int bar; }} obj.bar=5;
class Product {{ public int bar; }} obj.bar=5;
Make field public.
Java
name: test age: 20
name: test age: 20
Correct.
YAML
let mut foo=19; let r1=&mut foo; let ref2=&mut foo;
let mut foo=19; {{ let r1=&mut foo; }} let ref2=&mut foo;
Only one mutable borrow.
Rust
if val = 95
if val == 95
Use ==.
Go
if ($a = 57) {{}}
if ($a -eq 57) {{}}
Use -eq.
PowerShell
index == '17'
index === 17
Use strict equality.
JavaScript
val val = 74; val = 54
var val = 74; val = 54
Use var for reassignment.
Scala
y > 96 & a < 87
y > 96 and a < 87
Use 'and' not '&'.
Python
items[75]
if (length(items) >= 75) items[75]
Check length.
R
UPDATE products SET id='test' WHERE status=51
UPDATE products SET id='test' WHERE status=51;
Add semicolon.
SQL
cin >> bar cout << bar;
cin >> bar; cout << bar;
Add semicolon.
C++
$arr[16]
if ($arr.Count -gt 16) {{ $arr[16] }}
Check bounds.
PowerShell
<input type='text' value='hello'>
<input type='text' value='hello' name='age'>
Add name attribute.
HTML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
foo = result
foo = 'result'
Quote strings.
Python
for i=1,89 do print(i) end
for i=1,89 do print(i) end
Correct.
Lua
function compute() {{ echo 'hello'; }}
function compute() {{ echo 'hello'; }}
Correct.
PHP
List(49,76,14)
List(49,76,14)
Correct.
Scala
#content {{ color: #333; }}
#content {{ color: #333; }}
Correct.
CSS
<div color=#fff>
<div style='color:#fff;'>
Use style attribute.
CSS
INSERT INTO items VALUES ('test',15)
INSERT INTO items (id, role) VALUES ('test',15);
Specify columns.
SQL
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(37);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('output')); app.listen(37, () => console.log('listening'));
Add callback.
Node.js
<ul><li>data<li>hello</ul>
<ul><li>data</li><li>hello</li></ul>
Close li.
HTML
{{'status':'message'}}
{{"status":"message"}}
Use double quotes.
JSON
for (int i=0; i<5; i++) {{}}
for (int i=0; i<5; i++) {{}}
Correct.
Java
<person><age>test</age><age>72</age></person
<person><age>test</age><age>72</age></person>
Add closing >.
XML
<hr></hr>
<hr>
Self-closing.
HTML
if (c = 73)
if (c == 73)
Use ==.
R
arr[88]
if (arr.indices.contains(88)) arr[88]
Check index.
Kotlin
SELECT name role FROM items;
SELECT name, role FROM items;
Add comma.
SQL
id: result age: data,
id: result age: data
Remove comma.
YAML
jwt.sign({{id:52}}, 'key');
jwt.sign({{id:52}}, 'key', {{expiresIn:'7d'}});
Add expiration.
Node.js