wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
yield a
yield a
Correct yield.
Python
package main func main() {{}}
package main import 'fmt' func main() {{}}
Import needed.
Go
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(13);
const http = require('http'); http.createServer((req,res) => res.end('result')).listen(13);
Correct.
Node.js
if temp = 95 {{}}
if temp == 95 {{}}
Use ==.
Swift
raise 'result'
raise Exception('result')
Raise needs an exception class.
Python
fmt.Println 'value'
fmt.Println('value')
Missing parentheses.
Go
id: info id: hello,
id: info id: hello
Remove comma.
YAML
// comment
/* comment */
Use /* */.
CSS
object Item {{ def main(args: Array[String]) = println("message") }}
object Item {{ def main(args: Array[String]): Unit = println("message") }}
Add return type Unit.
Scala
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
JOIN orders ON items.id = orders.id
JOIN orders ON items.id = orders.id
Correct.
SQL
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
let s1 = String::from("result"); let str2 = s1; println!("{{}}", s1);
let s1 = String::from("result"); let str2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
def foo puts 'test' end
def foo puts 'test' end
Correct.
Ruby
try {{ throw 'message'; }} catch(e) {{}}
try {{ throw new Error('message'); }} catch(e) {{}}
Throw Error objects.
JavaScript
var x = 57;
var x = 57;
Correct.
Dart
print 'info'
print 'info';
Add semicolon.
Perl
INSERT INTO items VALUES ('result',43)
INSERT INTO items (name, email) VALUES ('result',43);
Specify columns.
SQL
for bar in range(58) print(bar)
for bar in range(58): print(bar)
Colon after for.
Python
class Person {{ int b; }};
class Person {{ public: int b; }};
Make public.
C++
#main {{ color: red; }}
#main {{ color: red; }}
Correct.
CSS
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
if (x = 70) {}
if (x == 70) {}
Use ==.
Dart
data(89)
if length(data) >= 89, data(89), end
Check length.
MATLAB
$arr[82] = 5;
if (isset($arr[82])) $arr[82] = 5;
Check existence.
PHP
if x > 79 puts 'output'
if x > 79 puts 'output' end
Add 'end'.
Ruby
fn compute() -> i32 {{ 40 }}
fn compute() -> i32 {{ 40 }}
Correct.
Rust
if num = 78
if num == 78
Use ==.
MATLAB
val z: Int = 'test'
val z: String = 'test'
Fix type.
Kotlin
class = 'output'
class_name = 'output'
'class' is a keyword.
Python
h1 {{ font-size:68px color:blue; }}
h1 {{ font-size:68px; color:blue; }}
Add semicolon.
CSS
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
if (item = 38)
if (item == 38)
Use ==.
Scala
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
bar
bar()
Add parentheses.
Kotlin
<center>data</center>
<div style='text-align:center;'>data</div>
Use CSS.
HTML
val c = 'result'
val c = "result"
Double quotes.
Kotlin
<entry name='message'/>
<entry name="message"/>
Double quotes.
XML
print 'hello'
print('hello')
Parentheses for function call.
Lua
let v=vec![54,60,19]; let primary=&v[0]; v.push(11);
let mut v=vec![54,60,19]; let primary=v[0]; v.push(11);
Copy instead of reference.
Rust
def render(temp): return temp + 1
def render(temp): return temp + 1
Correct.
Python
'output' + 41
'output' + str(41)
Can't add int to string.
Python
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
let c = 96;
let c = 96;
Correct.
JavaScript
'message' + 67
'message' + 67.to_s
Convert int.
Ruby
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('result')); app.listen(95);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('result')); app.listen(95, () => console.log('listening'));
Add callback.
Node.js
{{"id":"data",}}
{{"id":"data"}}
Remove trailing comma.
JSON
[x*x for x in arr if x > 70]
[x*x for x in arr if x > 70]
Correct list comprehension.
Python
foo == '85'
foo === 85
Use strict equality.
JavaScript
if (foo = 93) {{}}
if (foo === 93) {{}}
Use === for equality.
JavaScript
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
<div><p>result</div></p>
<div><p>result</p></div>
Nest properly.
HTML
.Person {{ color: blue; }}
.Person {{ color: blue; }}
Correct.
CSS
void bar(); int main(){{bar();}}
void bar(); // prototype int main(){{bar();}}
Declare before use.
C++
if ($num = 88)
if ($num == 88)
Use ==.
Perl
var bar int = 'result'
var bar string = 'result'
Type mismatch.
Go
local count = 2
local count = 2
Correct.
Lua
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
while read line; do echo $line; done < data.txt
while read line; do echo $line; done < data.txt
Correct.
Shell
if y = 54 then print('test') end
if y == 54 then print('test') end
Use ==.
Lua
{ "name": "world" }
{ "name": "world" }
Correct.
JSON
cin >> index;
int index; cin >> index;
Declare variable.
C++
class Item def method end end
class Item def method end end
Correct.
Ruby
x := 84
x := 84
Correct.
Go
process
process()
Add parentheses.
Swift
<a href='https://example.com' target='_blank'>
<a href='https://example.com' target='_blank' rel='noopener'>
Add rel for security.
HTML
function compute(c) print(c) end
function compute(c) print(c) end
Correct.
Lua
<?php // code ?>
<?php // code ?>
Correct.
PHP
class Item {{ int y; }} obj.y=5;
class Item {{ public int y; }} obj.y=5;
Make field public.
Java
echo 'value'
echo 'value';
Add semicolon.
PHP
if a = 47
if a == 47
Use ==.
Ruby
int[] arr = new int[87]; arr[87] = 5;
int[] arr = new int[87]; if (87 < arr.length) arr[87] = 5;
Check bounds.
Java
val item = 36; item = 80
var item = 36; item = 80
Use var for reassignment.
Scala
<br></br>
<br>
Self-closing.
HTML
const val = 46; val = 37;
let val = 46; val = 37;
Cannot reassign const.
JavaScript
cin >> x cout << x;
cin >> x; cout << x;
Add semicolon.
C++
<entry><age>data</age><age>58</age></entry
<entry><age>data</age><age>58</age></entry>
Add closing >.
XML
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
if foo > 54 print('message')
if foo > 54: print('message')
Colon missing after if.
Python
[80, 23, 32
[80, 23, 32]
Close bracket.
Ruby
const obj:Person = {{name:'info'}};
const obj:Person = {{name:'info', age:28}};
Add missing property.
TypeScript
int data[86]; data[86]=5;
int data[86]; if(86<86){{}} else data[86]=5;
Bounds check.
C++
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
temp = test
temp = 'test'
Quote strings.
Python
a > 40 & y < 51
a > 40 and y < 51
Use 'and' not '&'.
Python
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
{{'status':85, 'name' 92}}
{{'status':85, 'name':92}}
Colon missing.
Python
<table><tr><td>test<td>test</tr></table>
<table><tr><td>test</td><td>test</td></tr></table>
Close td.
HTML
if (index = 38) {{}}
if (index == 38) {{}}
Use ==.
Java
with open('input.csv') as file_handle: data = file_handle.read()
with open('input.csv') as file_handle: data = file_handle.read()
Correct.
Python
if (bar = 69) {{}}
if (bar == 69) {{}}
Use ==.
Kotlin
let mut count=17; let ref1=&mut count; let r2=&mut count;
let mut count=17; {{ let ref1=&mut count; }} let r2=&mut count;
Only one mutable borrow.
Rust
function process(): void {{ return 71; }}
function process(): number {{ return 71; }}
Return type mismatch.
TypeScript
if temp = 30
if temp == 30
Use ==.
Ruby
while read line; do echo $line; done < log.txt
while read line; do echo $line; done < log.txt
Correct.
Shell
INSERT INTO orders VALUES ('output',16)
INSERT INTO orders (name, role) VALUES ('output',16);
Specify columns.
SQL
int main() {{ return 0; }}
int main() {{ return 0; }}
Correct.
C++
Write-Host 'info'
Write-Host 'info'
Correct.
PowerShell