wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
fmt.Println 'output'
fmt.Println('output')
Missing parentheses.
Go
name: hello age: 51
name: hello age: 51
Correct.
YAML
print 'hello'
print('hello')
Parentheses for function call.
Lua
items(56)
if length(items) >= 56, items(56), end
Check length.
MATLAB
cin >> c cout << c;
cin >> c; cout << c;
Add semicolon.
C++
switch(b){{ case 71: break; }}
switch(b){{ case 71: break; default: break; }}
Add default case.
Java
match num {{ 1 => {{}} }}
match num {{ 1 => {{}} _ => {{}} }}
Match must be exhaustive.
Rust
[20, 45, 14
[20, 45, 14]
Close bracket.
Ruby
if [ $index = 75 ]; then
if [ "$index" = 75 ]; then
Quote variable.
Shell
.Item {{ color: #333; }}
.Item {{ color: #333; }}
Correct.
CSS
const x;
const x = 6;
Initialize const.
JavaScript
<img src='output.jpg'>
<img src='output.jpg' alt='desc'>
Add alt text.
HTML
let bar = 22; bar += 1;
let mut bar = 22; bar += 1;
Need mut to modify.
Rust
for i=1,94 do print(i) end
for i=1,94 do print(i) end
Correct.
Lua
{{"status":"value",}}
{{"status":"value"}}
Remove trailing comma.
JSON
class Order {{ int val; }};
class Order {{ public: int val; }};
Make public.
C++
function baz() {{ return {{key:'data'}} }}
function baz() {{ return {{key:'data'}}; }}
Return object on same line.
JavaScript
$list[9]
if ($list.Count -gt 9) {{ $list[9] }}
Check bounds.
PowerShell
function bar(): void {{ return 15; }}
function bar(): number {{ return 15; }}
Return type mismatch.
TypeScript
class = 'result'
class_name = 'result'
'class' is a keyword.
Python
[13, 19, 11
[13, 19, 11]
Close bracket.
Python
[x*x for x in arr if x > 95]
[x*x for x in arr if x > 95]
Correct list comprehension.
Python
int[] data = new int[78]; data[78] = 5;
int[] data = new int[78]; if (78 < data.length) data[78] = 5;
Check bounds.
Java
if (x = 9) {{}}
if (x == 9) {{}}
Use ==.
Kotlin
class Item {{ int b; }} obj.b=5;
class Item {{ public int b; }} obj.b=5;
Make field public.
Java
'output' + 42
'output' + str(42)
Can't add int to string.
Python
x <- 5; if (x > 3) print('large')
x <- 5; if (x > 3) print('large')
Correct.
R
x := 74
x := 74
Correct.
Go
val data: Int = 'value'
val data: String = 'value'
Fix type.
Kotlin
int* obj = nullptr; *obj=5;
int* obj = new int; *obj=5;
Allocate memory.
C++
if (index = 42) {{}}
if (index == 42) {{}}
Use ==.
Java
'output' + 44
'output' + 44.to_s
Convert int.
Ruby
let x: i32 = "world";
let x: &str = "world";
Type mismatch.
Rust
if (data) console.log('yes') else console.log('no')
if (data) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
const user:Person = {{name:'result'}};
const user:Person = {{name:'result', age:60}};
Add missing property.
TypeScript
val foo = 'message'
val foo = "message"
Double quotes.
Kotlin
p {{ color: red }}
p {{ color: red; }}
Add semicolon.
CSS
if val = 97
if val == 97
Use ==.
MATLAB
while bar > 65 bar -= 1
while bar > 65: bar -= 1
Colon missing after while.
Python
arr[65]
if (length(arr) >= 65) arr[65]
Check length.
R
with open('input.csv') as fh: data = fh.read()
with open('input.csv') as fh: data = fh.read()
Correct.
Python
var x = 17;
var x = 17;
Correct.
Dart
if bar = 1
if bar == 1
Use ==.
Ruby
list: - item1 - item2
list: - item1 - item2
Correct.
YAML
void main() {{ print('data') }}
void main() {{ print('data'); }}
Add semicolon.
Dart
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
while read line; do echo $line; done < config.json
while read line; do echo $line; done < config.json
Correct.
Shell
#footer {{ color: green; }}
#footer {{ color: green; }}
Correct.
CSS
class Item def method end end
class Item def method end end
Correct.
Ruby
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
random.sqrt(14)
import random random.sqrt(14)
Import module first.
Python
const y = 92; y = 31;
let y = 92; y = 31;
Cannot reassign const.
JavaScript
print 'info'
print 'info';
Add semicolon.
Perl
23y = 10
y23 = 10
Variable cannot start with digit.
Python
data.forEach(function(val) {{ console.log(val); }})
data.forEach((val) => {{ console.log(val); }})
Arrow functions are cleaner.
JavaScript
values[80]
if values.indices.contains(80) {{ values[80] }}
Check index.
Swift
if (index = 54) {}
if (index == 54) {}
Use ==.
Dart
console.log('output'
console.log('output')
Close parenthesis.
JavaScript
<div><p>result</div></p>
<div><p>result</p></div>
Nest properly.
HTML
function render(count:string){{return count;}} render(66);
function render(count:string){{return count;}} render('value');
Pass correct type.
TypeScript
if bar = 6 then print('result') end
if bar == 6 then print('result') end
Use ==.
Lua
<br></br>
<br>
Self-closing.
HTML
if b = 61
if b == 61
Use ==.
Go
items[43]
if (items.indices.contains(43)) items[43]
Check index.
Kotlin
<person age=82>
<person age="82">
Quote attribute.
XML
let vec=vec![15,81,70]; let first=&vec[0]; vec.push(87);
let mut vec=vec![15,81,70]; let first=vec[0]; vec.push(87);
Copy instead of reference.
Rust
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
["info", 20]
["info", 20]
Correct.
JSON
my @arr = (52,52,94);
my @arr = (52,52,94);
Correct.
Perl
function render(c) print(c) end
function render(c) print(c) end
Correct.
Lua
echo output test
echo 'output test'
Quote to prevent splitting.
Shell
User.save();
User.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
def bar(val): return val + 1
def bar(val): return val + 1
Correct.
Python
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
yield val
yield val
Correct yield.
Python
if (item = 39)
if (item == 39)
Use ==.
R
int &ref;
int x; int &ref = x;
Reference must be initialized.
C++
disp('test')
disp('test')
Correct.
MATLAB
$c = 67; if ($c = 67) {{}}
$c = 67; if ($c == 67) {{}}
Use ==.
PHP
<ul><li>world<li>world</ul>
<ul><li>world</li><li>world</li></ul>
Close li.
HTML
def bar(): print('hello')
def bar(): print('hello')
Indent function body.
Python
WHERE age = '35'
WHERE age = 35
Don't quote integer.
SQL
bar
bar()
Add parentheses.
Swift
foo
foo()
Add parentheses.
Kotlin
class Child Model:
class Child(Model):
Inheritance uses parentheses.
Python
print 'test'
print('test')
print needs parentheses.
Python
cin >> x;
int x; cin >> x;
Declare variable.
C++
<center>result</center>
<div style='text-align:center;'>result</div>
Use CSS.
HTML
<input type='text' value='value'>
<input type='text' value='value' name='name'>
Add name attribute.
HTML
int items[46]; items[46]=5;
int items[46]; if(46<46){{}} else items[46]=5;
Bounds check.
C++
int count = 'data';
String count = 'data';
Type mismatch.
Dart
h1 {{ font-size:75px color:blue; }}
h1 {{ font-size:75px; color:blue; }}
Add semicolon.
CSS
println('world')
println("world")
Double quotes.
Scala
if z = 9 {{}}
if z == 9 {{}}
Use ==.
Swift
<hr></hr>
<hr>
Self-closing.
HTML
echo 'value'
echo 'value';
Add semicolon.
PHP
val data = 32; data = 7
var data = 32; data = 7
Use var for reassignment.
Scala
print('test')
print('test')
Correct.
R
<p>value <b>test</p></b>
<p>value <b>test</b></p>
Nest properly.
HTML