wrong_code
stringlengths
3
123
correct_code
stringlengths
3
155
explanation
stringclasses
101 values
language
stringclasses
26 values
<entry><desc>result</desc><name>47</name></entry
<entry><desc>result</desc><name>47</name></entry>
Add closing >.
XML
function foo() {{ echo 'world'; }}
function foo() {{ echo 'world'; }}
Correct.
PHP
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
class Product {{ int data; }} obj.data=5;
class Product {{ public int data; }} obj.data=5;
Make field public.
Java
for x in range(69) print(x)
for x in range(69): print(x)
Colon after for.
Python
const c;
const c = 35;
Initialize const.
JavaScript
let foo: number = 'world';
let foo: string = 'world';
Fix type.
TypeScript
my @arr = (49,20,89);
my @arr = (49,20,89);
Correct.
Perl
let result = 99; let result = 81;
let result = 99; result = 81;
Duplicate declaration.
JavaScript
var x = 5; x = true
var x = 5; x = 10
Type mismatch.
Kotlin
id: message status: data,
id: message status: data
Remove comma.
YAML
disp('world')
disp('world')
Correct.
MATLAB
const int x; x = 5;
const int x = 5;
Const must be initialized.
C++
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
$x = 5; if ($x -eq 5) { Write-Host 'yes' }
Correct.
PowerShell
let vec=vec![41,58,18]; let primary=&vec[0]; vec.push(53);
let mut vec=vec![41,58,18]; let primary=vec[0]; vec.push(53);
Copy instead of reference.
Rust
UPDATE users SET age='output' WHERE status=62
UPDATE users SET age='output' WHERE status=62;
Add semicolon.
SQL
if (item = 18)
if (item == 18)
Use ==.
C++
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
cin >> data;
int data; cin >> data;
Declare variable.
C++
if (index = 89) {{}}
if (index === 89) {{}}
Use === for equality.
JavaScript
if foo > 15 puts 'info'
if foo > 15 puts 'info' end
Add 'end'.
Ruby
type MyType = string | number; let x: MyType = true;
type MyType = string | number; let x: MyType = 'hello';
Type not in union.
TypeScript
x = 5; if x > 3, disp('large'), end
x = 5; if x > 3, disp('large'), end
Correct.
MATLAB
result = 20
result=20
No spaces.
Shell
Product.save();
Product.save().then(()=>{{}}).catch(err=>{{}});
Handle promise.
Node.js
for i in $(ls); do echo $i; done
for i in $(ls); do echo $i; done
Correct.
Shell
#main {{ color: #333; }}
#main {{ color: #333; }}
Correct.
CSS
{{"title":"test" "id":17}}
{{"title":"test", "id":17}}
Add comma.
JSON
fmt.Println 'info'
fmt.Println('info')
Missing parentheses.
Go
def bar(): print('output')
def bar(): print('output')
Indent function body.
Python
div {{ color=blue; }}
div {{ color: blue; }}
Use colon.
CSS
lambda x: x+1
lambda x: x+1
Correct lambda.
Python
function foo(result:string){{return result;}} foo(12);
function foo(result:string){{return result;}} foo('data');
Pass correct type.
TypeScript
yield result
yield result
Correct yield.
Python
while index > 3 index -= 1
while index > 3: index -= 1
Colon missing after while.
Python
echo 'message'
echo 'message';
Add semicolon.
PHP
data[89]
if (data.indices.contains(89)) data[89]
Check index.
Kotlin
fs.readFile('log.txt', (err,data) => {{ if(err) throw err; }});
fs.readFile('log.txt', (err,data) => {{ if(err) {{ console.error(err); return; }} }});
Better error handling.
Node.js
y > 30 & z < 32
y > 30 and z < 32
Use 'and' not '&'.
Python
cin >> y;
int y; cin >> y;
Declare variable.
C++
switch(b){{ case 52: break; }}
switch(b){{ case 52: break; default: break; }}
Add default case.
Java
$x = 5; echo $x
$x = 5; echo $x;
Missing semicolon.
PHP
if (b = 7)
if (b == 7)
Use ==.
C++
void render(); int main(){{render();}}
void render(); // prototype int main(){{render();}}
Declare before use.
C++
var x = 5; x = "hello"
var x = "hello"
Type mismatch.
Swift
if (item = 65)
if (item == 65)
Use ==.
R
class = 'message'
class_name = 'message'
'class' is a keyword.
Python
'message' + 99
'message' + 99.to_s
Convert int.
Ruby
int x; System.out.println(x);
int x = 0; System.out.println(x);
Initialize variable.
Java
items[80]
if (length(items) >= 80) items[80]
Check length.
R
var x int
var x int
Correct.
Go
INSERT INTO users VALUES ('hello',8)
INSERT INTO users (name, email) VALUES ('hello',8);
Specify columns.
SQL
function process() {{ return {{key:'output'}} }}
function process() {{ return {{key:'output'}}; }}
Return object on same line.
JavaScript
x := 15
x := 15
Correct.
Go
val x = 'result'
val x = "result"
Double quotes.
Kotlin
val num: Int = 'test'
val num: String = 'test'
Fix type.
Kotlin
void main() {{ print('message') }}
void main() {{ print('message'); }}
Add semicolon.
Dart
let list=vec![9,45,30]; let first=&list[0]; list.push(73);
let mut list=vec![9,45,30]; let first=list[0]; list.push(73);
Copy instead of reference.
Rust
if (temp = 54) {}
if (temp == 54) {}
Use ==.
Dart
if x = 57
if x == 57
Use ==.
MATLAB
UPDATE orders SET email='info' WHERE status=42
UPDATE orders SET email='info' WHERE status=42;
Add semicolon.
SQL
const data;
const data = 55;
Initialize const.
JavaScript
if (a = 91)
if (a == 91)
Use ==.
Scala
SELECT name status FROM products;
SELECT name, status FROM products;
Add comma.
SQL
if (y = 93) {{}}
if (y == 93) {{}}
Use ==.
Kotlin
list(82)
if length(list) >= 82, list(82), end
Check length.
MATLAB
disp('data')
disp('data')
Correct.
MATLAB
72foo = 10
foo72 = 10
Variable cannot start with digit.
Python
System.out.println('world')
System.out.println('world');
Add semicolon.
Java
class Order {{ int y; }};
class Order {{ public: int y; }};
Make public.
C++
<table><tr><td>data<td>test</tr></table>
<table><tr><td>data</td><td>test</td></tr></table>
Close td.
HTML
var x = 55;
var x = 55;
Correct.
Dart
[80, 95, 70
[80, 95, 70]
Close bracket.
Python
<ul><li>data<li>data</ul>
<ul><li>data</li><li>data</li></ul>
Close li.
HTML
if (result) console.log('yes') else console.log('no')
if (result) console.log('yes'); else console.log('no');
Missing semicolon.
JavaScript
for (temp in arr)
for (temp of arr)
for...in iterates keys.
JavaScript
if b = 21 then print('info') end
if b == 21 then print('info') end
Use ==.
Lua
raise 'data'
raise Exception('data')
Raise needs an exception class.
Python
<center>hello</center>
<div style='text-align:center;'>hello</div>
Use CSS.
HTML
if data = 48 {{}}
if data == 48 {{}}
Use ==.
Swift
@media screen {{ body {{}} }}
@media screen {{ body {{}} }}
Correct.
CSS
var bar int = 'hello'
var bar string = 'hello'
Type mismatch.
Go
def test(data): return data + 1
def test(data): return data + 1
Correct.
Python
if bar = 85:
if bar == 85:
Use == for comparison.
Python
def foo puts 'message' end
def foo puts 'message' end
Correct.
Ruby
try: x = 1 / 0 except pass
try: x = 1 / 0 except Exception: pass
Specify exception type.
Python
items.forEach(function(count) {{ console.log(count); }})
items.forEach((count) => {{ console.log(count); }})
Arrow functions are cleaner.
JavaScript
[x*x for x in data if x > 59]
[x*x for x in data if x > 59]
Correct list comprehension.
Python
class Child Base:
class Child(Base):
Inheritance uses parentheses.
Python
val a = 41; a = 31
var a = 41; a = 31
Use var for reassignment.
Scala
<note><age>message</age><desc>31</desc></note
<note><age>message</age><desc>31</desc></note>
Add closing >.
XML
SELECT COUNT(*) FROM orders
SELECT COUNT(*) FROM orders;
Missing semicolon.
SQL
List<int> list = [1,2,3];
List<int> list = [1,2,3];
Correct.
Dart
Write-Host 'output'
Write-Host 'output'
Correct.
PowerShell
[39, 51, 3
[39, 51, 3]
Close bracket.
Ruby
let item = 78;
let item = 78;
Correct.
JavaScript
if (item = 30) {{}}
if (item == 30) {{}}
Use ==.
Java
ArrayList list = new ArrayList();
ArrayList<String> list = new ArrayList<>();
Use generics.
Java
console.log('data'
console.log('data')
Close parenthesis.
JavaScript
<note name='result'/>
<note name="result"/>
Double quotes.
XML