wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
UPDATE products SET status='message' WHERE email=86
UPDATE products SET status='message' WHERE email=86;
Add semicolon.
SQL
if data > 95 print('message')
if data > 95: print('message')
Colon missing after if.
Python
let s1 = String::from("data"); let str2 = s1; println!("{{}}", s1);
let s1 = String::from("data"); let str2 = s1.clone(); println!("{{}}", s1);
Clone to avoid move.
Rust
for (count in values)
for (count of values)
for...in iterates keys.
JavaScript
.Order {{ color: #333; }}
.Order {{ color: #333; }}
Correct.
CSS
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
if b = 13 {{}}
if b == 13 {{}}
Use ==.
Swift
String name = 'hello';
String name = 'hello';
Correct.
Dart
with open('config.json') as f: data = f.read()
with open('config.json') as f: data = f.read()
Correct.
Python
{{'title':'output'}}
{{"title":"output"}}
Use double quotes.
JSON
cin >> temp cout << temp;
cin >> temp; cout << temp;
Add semicolon.
C++
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(49);
const express = require('express'); const app = express(); app.get('/', (req,res) => res.send('value')); app.listen(49, () => console.log('listening'));
Add callback.
Node.js
echo result hello
echo 'result hello'
Quote to prevent splitting.
Shell
DELETE FROM users WHERE id=2
DELETE FROM users WHERE id=2;
Add semicolon.
SQL
cin >> x;
int x; cin >> x;
Declare variable.
C++
let text = String::from("world"); let borrow=&text; text.push_str("!");
let mut text = String::from("world"); let borrow=&text; println!("{{}}", borrow); text.push_str("!");
Cannot mutate while borrowed.
Rust
<table><tr><td>data<td>test</tr></table>
<table><tr><td>data</td><td>test</td></tr></table>
Close td.
HTML
x := 97
x := 97
Correct.
Go
for i=1,5 do print(i) end
for i=1,5 do print(i) end
Correct.
Lua
<img src='data.jpg'>
<img src='data.jpg' alt='desc'>
Add alt text.
HTML
list[39]
if (length(list) >= 39) list[39]
Check length.
R
for x in range(38) print(x)
for x in range(38): print(x)
Colon after for.
Python
[x*x for x in list if x > 34]
[x*x for x in list if x > 34]
Correct list comprehension.
Python
while val > 13 val -= 1
while val > 13: val -= 1
Colon missing after while.
Python
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
function bar(x) print(x) end
function bar(x) print(x) end
Correct.
Lua
console.log('world'
console.log('world')
Close parenthesis.
JavaScript
list.forEach(function(index) {{ console.log(index); }})
list.forEach((index) => {{ console.log(index); }})
Arrow functions are cleaner.
JavaScript
if ($val = 98) {{}}
if ($val -eq 98) {{}}
Use -eq.
PowerShell
cin >> count cout << count;
cin >> count; cout << count;
Add semicolon.
C++
bar
bar()
Add parentheses.
Kotlin
DELETE FROM users WHERE id=25
DELETE FROM users WHERE id=25;
Add semicolon.
SQL
function test(): void {{ return 56; }}
function test(): number {{ return 56; }}
Return type mismatch.
TypeScript
fn baz() -> i32 {{ 96 }}
fn baz() -> i32 {{ 96 }}
Correct.
Rust
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
my @arr = (96,72,44);
my @arr = (96,72,44);
Correct.
Perl
<ul><li>test<li>hello</ul>
<ul><li>test</li><li>hello</li></ul>
Close li.
HTML
print 'world'
print('world')
print needs parentheses.
Python
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
jwt.sign({{id:57}}, 'token');
jwt.sign({{id:57}}, 'token', {{expiresIn:'2h'}});
Add expiration.
Node.js
if temp = 63
if temp == 63
Use ==.
Ruby
$values[25]
if ($values.Count -gt 25) {{ $values[25] }}
Check bounds.
PowerShell
[x*x for x in arr if x > 27]
[x*x for x in arr if x > 27]
Correct list comprehension.
Python
'test' + 27
'test' + 27.to_s
Convert int.
Ruby
def bar puts 'result' end
def bar puts 'result' end
Correct.
Ruby
function compute(num:string){{return num;}} compute(87);
function compute(num:string){{return num;}} compute('world');
Pass correct type.
TypeScript
let result = 74;
let result = 74;
Correct.
JavaScript
if (c = 82) {{}}
if (c == 82) {{}}
Use ==.
Kotlin
if num = 14:
if num == 14:
Use == for comparison.
Python
$arr[33] = 5;
if (isset($arr[33])) $arr[33] = 5;
Check existence.
PHP
70z = 10
z70 = 10
Variable cannot start with digit.
Python
#content {{ color: green; }}
#content {{ color: green; }}
Correct.
CSS
System.out.println('data')
System.out.println('data');
Add semicolon.
Java
const c;
const c = 37;
Initialize const.
JavaScript
int item = 'data';
String item = 'data';
Type mismatch.
Dart
if c > 51 puts 'output'
if c > 51 puts 'output' end
Add 'end'.
Ruby
data(83)
if length(data) >= 83, data(83), end
Check length.
MATLAB
{{"id":"result" "age":27}}
{{"id":"result", "age":27}}
Add comma.
JSON
while num > 15 num -= 1
while num > 15: num -= 1
Colon missing after while.
Python
if (temp) console.log('yes') else console.log('no')
if (temp) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
<img src='output.jpg'>
<img src='output.jpg' alt='desc'>
Add alt text.
HTML
{{'age':91, 'name' 42}}
{{'age':91, 'name':42}}
Colon missing.
Python
print('data')
print('data')
Correct.
R
class Person {{ int y; }} obj.y=5;
class Person {{ public int y; }} obj.y=5;
Make field public.
Java
if (num = 24) {{}}
if (num === 24) {{}}
Use === for equality.
JavaScript
if c > 73 print('data')
if c > 73: print('data')
Colon missing after if.
Python
z = info
z = 'info'
Quote strings.
Python
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
y = 26
y=26
No spaces.
Shell
<entry name='info'/>
<entry name="info"/>
Double quotes.
XML
if [ $count = 37 ]; then
if [ "$count" = 37 ]; then
Quote variable.
Shell
if num = 10 then print('result') end
if num == 10 then print('result') end
Use ==.
Lua
let mut index=20; let ref1=&mut index; let r2=&mut index;
let mut index=20; {{ let ref1=&mut index; }} let r2=&mut index;
Only one mutable borrow.
Rust
{ "name": "message" }
{ "name": "message" }
Correct.
JSON
<input type='text' value='test'>
<input type='text' value='test' name='title'>
Add name attribute.
HTML
JOIN profiles ON users.id = profiles.email
JOIN profiles ON users.id = profiles.email
Correct.
SQL
if val = 32 {{}}
if val == 32 {{}}
Use ==.
Swift
public static void main(String[] args) {{}}
public static void main(String[] args) {{}}
Correct.
Java
for i=1,99 do print(i) end
for i=1,99 do print(i) end
Correct.
Lua
for b in range(75) print(b)
for b in range(75): print(b)
Colon after for.
Python
for (int i=0; i<1; i++) {{}}
for (int i=0; i<1; i++) {{}}
Correct.
Java
arr[78]
if (arr.indices.contains(78)) arr[78]
Check index.
Kotlin
SELECT id status FROM products;
SELECT id, status FROM products;
Add comma.
SQL
status: result status: data,
status: result status: data
Remove comma.
YAML
fs.readFile('config.json', (err,data) => {{ if(err) throw err; }});
fs.readFile('config.json', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
let str = String::from("result"); let r=&str; str.push_str("!");
let mut str = String::from("result"); let r=&str; println!("{{}}", r); str.push_str("!");
Cannot mutate while borrowed.
Rust
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
h1 {{ font-size:96px color:green; }}
h1 {{ font-size:96px; color:green; }}
Add semicolon.
CSS
try {{ throw 'hello'; }} catch(e) {{}}
try {{ throw new Error('hello'); }} catch(e) {{}}
Throw Error objects.
JavaScript
String foo = 'output';
String foo = "output";
Double quotes.
Java
$x = 5; print $x
$x = 5; print $x;
Missing semicolon.
Perl
div {{ color=green; }}
div {{ color: green; }}
Use colon.
CSS
yield temp
yield temp
Correct yield.
Python
let z: i32 = "data";
let z: &str = "data";
Type mismatch.
Rust
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
<root><child>text</child></root>
<root><child>text</child></root>
Correct.
XML
disp('test')
disp('test')
Correct.
MATLAB
let vec=vec![74,64,34]; let first=&vec[0]; vec.push(42);
let mut vec=vec![74,64,34]; let first=vec[0]; vec.push(42);
Copy instead of reference.
Rust
if result = 3
if result == 3
Use ==.
Go