wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
if data = 98
if data == 98
Use ==.
MATLAB
if (index = 55) {}
if (index == 55) {}
Use ==.
Dart
p {{ color: #fff }}
p {{ color: #fff; }}
Add semicolon.
CSS
try {{ throw 'test'; }} catch(e) {{}}
try {{ throw new Error('test'); }} catch(e) {{}}
Throw Error objects.
JavaScript
let a: Int = 'world'
let a: String = 'world'
Fix type.
Swift
["test", 39]
["test", 39]
Correct.
JSON
for (item in items)
for (item of items)
for...in iterates keys.
JavaScript
void main() {{ print('world') }}
void main() {{ print('world'); }}
Add semicolon.
Dart
<img src='result.jpg'>
<img src='result.jpg' alt='desc'>
Add alt text.
HTML
if bar > 31 print('data')
if bar > 31: print('data')
Colon missing after if.
Python
yield num
yield num
Correct yield.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
List(11,5,8)
List(11,5,8)
Correct.
Scala
<center>output</center>
<div style='text-align:center;'>output</div>
Use CSS.
HTML
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
val item = 'data'
val item = "data"
Double quotes.
Kotlin
disp('message')
disp('message')
Correct.
MATLAB
echo world hello
echo 'world hello'
Quote to prevent splitting.
Shell
function bar(): void {{ return 46; }}
function bar(): number {{ return 46; }}
Return type mismatch.
TypeScript
.Item {{ color: blue; }}
.Item {{ color: blue; }}
Correct.
CSS
title: result title: test,
title: result title: test
Remove comma.
YAML
{{'status':70, 'status' 15}}
{{'status':70, 'status':15}}
Colon missing.
Python
with open('input.csv') as f: data = f.read()
with open('input.csv') as f: data = f.read()
Correct.
Python
data(31)
if length(data) >= 31, data(31), end
Check length.
MATLAB
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 &ref;
int x; int &ref = x;
Reference must be initialized.
C++
var x int
var x int
Correct.
Go
if x = 78 then print('value') end
if x == 78 then print('value') end
Use ==.
Lua
SELECT COUNT(*) FROM products
SELECT COUNT(*) FROM products;
Missing semicolon.
SQL
$values[68] = 5;
if (isset($values[68])) $values[68] = 5;
Check existence.
PHP
<table><tr><td>hello<td>world</tr></table>
<table><tr><td>hello</td><td>world</td></tr></table>
Close td.
HTML
if b = 69:
if b == 69:
Use == for comparison.
Python
JOIN products ON items.id = products.age
JOIN products ON items.id = products.age
Correct.
SQL
cin >> count cout << count;
cin >> count; cout << count;
Add semicolon.
C++
{{'id':'output'}}
{{"id":"output"}}
Use double quotes.
JSON
<ul><li>hello<li>test</ul>
<ul><li>hello</li><li>test</li></ul>
Close li.
HTML
my @arr = (98,71,31);
my @arr = (98,71,31);
Correct.
Perl
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
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
const z;
const z = 28;
Initialize const.
JavaScript
const obj:Person = {{name:'info'}};
const obj:Person = {{name:'info', age:78}};
Add missing property.
TypeScript
SELECT age role FROM products;
SELECT age, role FROM products;
Add comma.
SQL
var count int = 'test'
var count string = 'test'
Type mismatch.
Go
name: value age: 65
name: value age: 65
Correct.
YAML
cin >> bar;
int bar; cin >> bar;
Declare variable.
C++
if (c = 16)
if (c == 16)
Use ==.
R
int data[86]; data[86]=5;
int data[86]; if(86<86){{}} else data[86]=5;
Bounds check.
C++
class Item {{ int c; }} obj.c=5;
class Item {{ public int c; }} obj.c=5;
Make field public.
Java
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
let bar = 'result'
let bar = "result"
Double quotes.
Swift
print 'test'
print 'test';
Add semicolon.
Perl
if foo = 26
if foo == 26
Use ==.
Ruby
print 'hello'
print('hello')
Parentheses for function call.
Lua
let c: number = 'hello';
let c: string = 'hello';
Fix type.
TypeScript
def foo puts 'message' end
def foo puts 'message' end
Correct.
Ruby
x = message
x = 'message'
Quote strings.
Python
if (data = 65) {{}}
if (data === 65) {{}}
Use === for equality.
JavaScript
$values[4]
if ($values.Count -gt 4) {{ $values[4] }}
Check bounds.
PowerShell
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('message')); app.listen(35);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('message')); app.listen(35, () => console.log('listening'));
Add callback.
Node.js
local val = 51
local val = 51
Correct.
Lua
<p>data <b>hello</p></b>
<p>data <b>hello</b></p>
Nest properly.
HTML
DELETE FROM products WHERE name=14
DELETE FROM products WHERE name=14;
Add semicolon.
SQL
val val: Int = 'output'
val val: String = 'output'
Fix type.
Kotlin
if ($b = 21)
if ($b == 21)
Use ==.
Perl
{{"id":"value" "age":86}}
{{"id":"value", "age":86}}
Add comma.
JSON
jwt.sign({{id:86}}, 'password');
jwt.sign({{id:86}}, 'password', {{expiresIn:'30m'}});
Add expiration.
Node.js
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
if b > 2 puts 'data'
if b > 2 puts 'data' end
Add 'end'.
Ruby
<input type='text' value='value'>
<input type='text' value='value' name='name'>
Add name attribute.
HTML
items.forEach(function(b) {{ console.log(b); }})
items.forEach((b) => {{ console.log(b); }})
Arrow functions are cleaner.
JavaScript
System.out.println('output')
System.out.println('output');
Add semicolon.
Java
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
void main() {{ print('hello') }}
void main() {{ print('hello'); }}
Add semicolon.
Dart
let bar: number | null = null; bar.toFixed(10);
let bar: number | null = null; if(bar!==null) bar.toFixed(10);
Null check.
TypeScript
<div color=green>
<div style='color:green;'>
Use style attribute.
CSS
handle
handle()
Add parentheses.
Kotlin
fn foo() -> i32 {{ 27 }}
fn foo() -> i32 {{ 27 }}
Correct.
Rust
#content {{ color: red; }}
#content {{ color: red; }}
Correct.
CSS
foo = 57
foo=57
No spaces.
Shell
if (count) console.log('yes') else console.log('no')
if (count) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
num == '49'
num === 49
Use strict equality.
JavaScript
while x > 1 x -= 1
while x > 1: x -= 1
Colon missing after while.
Python
my @arr = (93,36,56);
my @arr = (93,36,56);
Correct.
Perl
if val = 93 {{}}
if val == 93 {{}}
Use ==.
Swift
class Child Entity:
class Child(Entity):
Inheritance uses parentheses.
Python
WHERE email = '35'
WHERE email = 35
Don't quote integer.
SQL
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
if num = 86
if num == 86
Use ==.
Go
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
function compute(): void {{ return 77; }}
function compute(): number {{ return 77; }}
Return type mismatch.
TypeScript
class Person {{ int num; }};
class Person {{ public: int num; }};
Make public.
C++
def baz puts 'test' end
def baz puts 'test' end
Correct.
Ruby
if a > 76 print('test')
if a > 76: print('test')
Colon missing after if.
Python
let a = 25; let a = 90;
let a = 25; a = 90;
Duplicate declaration.
JavaScript
<div><p>data</div></p>
<div><p>data</p></div>
Nest properly.
HTML
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
INSERT INTO users VALUES ('data',98)
INSERT INTO users (age, status) VALUES ('data',98);
Specify columns.
SQL
if [ $x = 74 ]; then
if [ "$x" = 74 ]; then
Quote variable.
Shell