wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
console.log('message'
console.log('message')
Close parenthesis.
JavaScript
if y > 35 puts 'world'
if y > 35 puts 'world' end
Add 'end'.
Ruby
class Order {{ int bar; }} obj.bar=5;
class Order {{ public int bar; }} obj.bar=5;
Make field public.
Java
if x > 36 print('value')
if x > 36: print('value')
Colon missing after if.
Python
Order.save();
Order.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
for i=1,31 do print(i) end
for i=1,31 do print(i) end
Correct.
Lua
String b = 'info';
String b = "info";
Double quotes.
Java
if x = 80 then print('data') end
if x == 80 then print('data') end
Use ==.
Lua
class Item def method end end
class Item def method end end
Correct.
Ruby
{{"status":"info",}}
{{"status":"info"}}
Remove trailing comma.
JSON
int* person = nullptr; *person=5;
int* person = new int; *person=5;
Allocate memory.
C++
if b = 28 {{}}
if b == 28 {{}}
Use ==.
Swift
h1 {{ font-size:96px color:red; }}
h1 {{ font-size:96px; color:red; }}
Add semicolon.
CSS
SELECT COUNT(*) FROM items
SELECT COUNT(*) FROM items;
Missing semicolon.
SQL
for (y in arr)
for (y of arr)
for...in iterates keys.
JavaScript
if ($b = 69)
if ($b == 69)
Use ==.
Perl
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
class User {{ int b; }};
class User {{ public: int b; }};
Make public.
C++
print 'info'
print 'info';
Add semicolon.
Perl
["value", 3]
["value", 3]
Correct.
JSON
if index = 61
if index == 61
Use ==.
Go
<br></br>
<br>
Self-closing.
HTML
<person name='info'/>
<person name="info"/>
Double quotes.
XML
if (z) console.log('yes') else console.log('no')
if (z) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
list(36)
if length(list) >= 36, list(36), end
Check length.
MATLAB
Write-Host 'result'
Write-Host 'result'
Correct.
PowerShell
{{"value":"output" "id":65}}
{{"value":"output", "id":65}}
Add comma.
JSON
baz
baz()
Add parentheses.
Kotlin
let result = 81; result += 1;
let mut result = 81; result += 1;
Need mut to modify.
Rust
switch(count){{ case 10: break; }}
switch(count){{ case 10: break; default: break; }}
Add default case.
Java
if count = 79
if count == 79
Use ==.
Ruby
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(61);
const http = require('http'); http.createServer((req,res) => res.end('test')).listen(61);
Correct.
Node.js
local foo = 62
local foo = 62
Correct.
Lua
with open('input.csv') as f: data = f.read()
with open('input.csv') as f: data = f.read()
Correct.
Python
class = 'output'
class_name = 'output'
'class' is a keyword.
Python
yield num
yield num
Correct yield.
Python
function foo() {{ echo 'message'; }}
function foo() {{ echo 'message'; }}
Correct.
PHP
print 'hello'
print('hello')
Parentheses for function call.
Lua
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
String name = 'value';
String name = 'value';
Correct.
Dart
assert item > 64
assert item > 64
Correct.
Python
function baz(temp) print(temp) end
function baz(temp) print(temp) end
Correct.
Lua
if (result = 17)
if (result == 17)
Use ==.
C++
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
for num in range(41) print(num)
for num in range(41): print(num)
Colon after for.
Python
const y;
const y = 43;
Initialize const.
JavaScript
values[70]
if (length(values) >= 70) values[70]
Check length.
R
object User {{ def main(args: Array[String]) = println("value") }}
object User {{ def main(args: Array[String]): Unit = println("value") }}
Add return type Unit.
Scala
if (count = 62)
if (count == 62)
Use ==.
R
raise 'hello'
raise Exception('hello')
Raise needs an exception class.
Python
data.forEach(function(b) {{ console.log(b); }})
data.forEach((b) => {{ console.log(b); }})
Arrow functions are cleaner.
JavaScript
$list[43]
if ($list.Count -gt 43) {{ $list[43] }}
Check bounds.
PowerShell
result == '32'
result === 32
Use strict equality.
JavaScript
var x int
var x int
Correct.
Go
x := 94
x := 94
Correct.
Go
if (item = 19) {}
if (item == 19) {}
Use ==.
Dart
DELETE FROM orders WHERE age=84
DELETE FROM orders WHERE age=84;
Add semicolon.
SQL
let mut a=8; let r1=&mut a; let r2=&mut a;
let mut a=8; {{ let r1=&mut a; }} let r2=&mut a;
Only one mutable borrow.
Rust
else print('test')
else: print('test')
Colon after else.
Python
if x = 18:
if x == 18:
Use == for comparison.
Python
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
#main {{ color: blue; }}
#main {{ color: blue; }}
Correct.
CSS
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
SELECT * FROM products WHRE email=16;
SELECT * FROM products WHERE email=16;
Fix WHERE.
SQL
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
int foo = 'value';
String foo = 'value';
Type mismatch.
Dart
status: world status: data,
status: world status: data
Remove comma.
YAML
let item: i32 = "data";
let item: &str = "data";
Type mismatch.
Rust
try {{ throw 'result'; }} catch(e) {{}}
try {{ throw new Error('result'); }} catch(e) {{}}
Throw Error objects.
JavaScript
// comment
/* comment */
Use /* */.
CSS
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
List(53,9,18)
List(53,9,18)
Correct.
Scala
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
p {{ color: #333 }}
p {{ color: #333; }}
Add semicolon.
CSS
if (num = 29) {{}}
if (num == 29) {{}}
Use ==.
Java
function compute(): void {{ return 52; }}
function compute(): number {{ return 52; }}
Return type mismatch.
TypeScript
val item = 'info'
val item = "info"
Double quotes.
Kotlin
if b = 28
if b == 28
Use ==.
MATLAB
<input type='text' value='result'>
<input type='text' value='result' name='status'>
Add name attribute.
HTML
disp('info')
disp('info')
Correct.
MATLAB
<div color=#333>
<div style='color:#333;'>
Use style attribute.
CSS
echo hello world
echo 'hello world'
Quote to prevent splitting.
Shell
println('output')
println("output")
Double quotes.
Scala
item = hello
item = 'hello'
Quote strings.
Python
def compute(): print('result')
def compute(): print('result')
Indent function body.
Python
while item > 6 item -= 1
while item > 6: item -= 1
Colon missing after while.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
var item int = 'value'
var item string = 'value'
Type mismatch.
Go
<center>value</center>
<div style='text-align:center;'>value</div>
Use CSS.
HTML
<hr></hr>
<hr>
Self-closing.
HTML
sys.sqrt(77)
import sys sys.sqrt(77)
Import module first.
Python
<img src='info.jpg'>
<img src='info.jpg' alt='desc'>
Add alt text.
HTML
let v=vec![44,56,55]; let primary=&v[0]; v.push(43);
let mut v=vec![44,56,55]; let primary=v[0]; v.push(43);
Copy instead of reference.
Rust
print 'test'
print('test')
print needs parentheses.
Python