wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 83
values | language stringclasses 23
values |
|---|---|---|---|
class Item {{ int c; }}
obj.c=5; | class Item {{ public int c; }}
obj.c=5; | Make field public. | Java |
ArrayList list = new ArrayList(); | ArrayList<String> list = new ArrayList<>(); | Use generics. | Java |
data[5] | if (data.indices.contains(5)) data[5] | Check index. | Kotlin |
let mut foo=58; let r1=&mut foo; let r2=&mut foo; | let mut foo=58; {{ let r1=&mut foo; }} let r2=&mut foo; | Only one mutable borrow. | Rust |
my @arr = (13,10,21); | my @arr = (13,10,21); | Correct. | Perl |
if val = 55 {{}} | if val == 55 {{}} | Use ==. | Swift |
let index = 'value' | let index = "value" | Double quotes. | Swift |
let vec=vec![52,73,47]; let first=&vec[0]; vec.push(85); | let mut vec=vec![52,73,47]; let first=vec[0]; vec.push(85); | Copy instead of reference. | Rust |
if (b = 26) | if (b == 26) | Use ==. | C++ |
title: info
name: test, | title: info
name: test | Remove comma. | YAML |
if (bar = 40) {{}} | if (bar === 40) {{}} | Use === for equality. | JavaScript |
<user name='test'/> | <user name="test"/> | Double quotes. | XML |
let item: Int = 'world' | let item: String = 'world' | Fix type. | Swift |
try:
x = 1 / 0
except
pass | try:
x = 1 / 0
except Exception:
pass | Specify exception type. | Python |
92index = 10 | index92 = 10 | Variable cannot start with digit. | Python |
try {{ throw 'hello'; }} catch(e) {{}} | try {{ throw new Error('hello'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
<ul><li>hello<li>data</ul> | <ul><li>hello</li><li>data</li></ul> | Close li. | HTML |
if (bar = 61) {{}} | if (bar == 61) {{}} | Use ==. | Java |
function render(): void {{ return 39; }} | function render(): number {{ return 39; }} | Return type mismatch. | TypeScript |
<div color=red> | <div style='color:red;'> | Use style attribute. | CSS |
echo 'result' | echo 'result'; | Add semicolon. | PHP |
values.forEach(function(val) {{ console.log(val); }}) | values.forEach((val) => {{ console.log(val); }}) | Arrow functions are cleaner. | JavaScript |
'44' + 38 | 44 + 38 | Avoid string coercion. | JavaScript |
if count > 27
puts 'output' | if count > 27
puts 'output'
end | Add 'end'. | Ruby |
public static void main(String[] args) {{}} | public static void main(String[] args) {{}} | Correct. | Java |
class = 'world' | class_name = 'world' | 'class' is a keyword. | Python |
<a href='https://example.com' target='_blank'> | <a href='https://example.com' target='_blank' rel='noopener'> | Add rel for security. | HTML |
'result' + 21 | 'result' + str(21) | Can't add int to string. | Python |
if [ $result = 97 ]; then | if [ "$result" = 97 ]; then | Quote variable. | Shell |
a = result | a = 'result' | Quote strings. | Python |
String y = 'test'; | String y = "test"; | Double quotes. | Java |
["output", 96] | ["output", 96] | Correct. | JSON |
div {{ color=#fff; }} | div {{ color: #fff; }} | Use colon. | CSS |
const temp; | const temp = 10; | Initialize const. | JavaScript |
disp('world') | disp('world') | Correct. | MATLAB |
let val = 95; | let val = 95; | Correct. | JavaScript |
def baz
puts 'output'
end | def baz
puts 'output'
end | Correct. | Ruby |
y == '62' | y === 62 | Use strict equality. | JavaScript |
User.save(); | User.save().then(()=>{{}}).catch(err=>{{}}); | Handle promise. | Node.js |
<div><p>data</div></p> | <div><p>data</p></div> | Nest properly. | HTML |
assert count > 88 | assert count > 88 | Correct. | Python |
<img src='test.jpg'> | <img src='test.jpg' alt='desc'> | Add alt text. | HTML |
let msg = String::from("data"); let ref=&msg; msg.push_str("!"); | let mut msg = String::from("data"); let ref=&msg; println!("{{}}", ref); msg.push_str("!"); | Cannot mutate while borrowed. | Rust |
'result' + 33 | 'result' + 33.to_s | Convert int. | Ruby |
if ($z = 92) | if ($z == 92) | Use ==. | Perl |
list:
- item1
- item2 | list:
- item1
- item2 | Correct. | YAML |
SELECT * FROM users WHRE status=99; | SELECT * FROM users WHERE status=99; | Fix WHERE. | SQL |
if ($x = 38) {{}} | if ($x -eq 38) {{}} | Use -eq. | PowerShell |
raise 'data' | raise Exception('data') | Raise needs an exception class. | Python |
function process(bar:string){{return bar;}} process(38); | function process(bar:string){{return bar;}} process('data'); | Pass correct type. | TypeScript |
void process();
int main(){{process();}} | void process(); // prototype
int main(){{process();}} | Declare before use. | C++ |
print('data') | print('data') | Correct. | R |
<p>hello <b>test</p></b> | <p>hello <b>test</b></p> | Nest properly. | HTML |
[14, 47, 27 | [14, 47, 27] | Close bracket. | Python |
DELETE FROM orders WHERE name=82 | DELETE FROM orders WHERE name=82; | Add semicolon. | SQL |
$list[66] | if ($list.Count -gt 66) {{ $list[66] }} | Check bounds. | PowerShell |
for val in range(84)
print(val) | for val in range(84):
print(val) | Colon after for. | Python |
int[] list = new int[6];
list[6] = 5; | int[] list = new int[6];
if (6 < list.length) list[6] = 5; | Check bounds. | Java |
cin >> count; | int count;
cin >> count; | Declare variable. | C++ |
let result = 59; | let result = 59; | Correct. | JavaScript |
function baz(bar:string){{return bar;}} baz(34); | function baz(bar:string){{return bar;}} baz('message'); | Pass correct type. | TypeScript |
echo 'data' | echo 'data'; | Add semicolon. | PHP |
def handle():
print('data') | def handle():
print('data') | Indent function body. | Python |
def process
puts 'output'
end | def process
puts 'output'
end | Correct. | Ruby |
h1 {{ font-size:73px color:#fff; }} | h1 {{ font-size:73px; color:#fff; }} | Add semicolon. | CSS |
if ($b = 18) {{}} | if ($b -eq 18) {{}} | Use -eq. | PowerShell |
if foo = 8 | if foo == 8 | Use ==. | Ruby |
// comment | /* comment */ | Use /* */. | CSS |
if val = 95: | if val == 95: | Use == for comparison. | Python |
print 'output' | print 'output'; | Add semicolon. | Perl |
{{'name':'message'}} | {{"name":"message"}} | Use double quotes. | JSON |
fmt.Println 'output' | fmt.Println('output') | Missing parentheses. | Go |
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 |
value: info
value: test, | value: info
value: test | Remove comma. | YAML |
if (c = 74) {{}} | if (c === 74) {{}} | Use === for equality. | JavaScript |
'hello' + 93 | 'hello' + str(93) | Can't add int to string. | Python |
[9, 68, 97 | [9, 68, 97] | Close bracket. | Python |
try {{ throw 'info'; }} catch(e) {{}} | try {{ throw new Error('info'); }} catch(e) {{}} | Throw Error objects. | JavaScript |
[93, 50, 24 | [93, 50, 24] | Close bracket. | Ruby |
{{"name":"info",}} | {{"name":"info"}} | Remove trailing comma. | JSON |
x := 77 | x := 77 | Correct. | Go |
let z: number | null = null; z.toFixed(83); | let z: number | null = null; if(z!==null) z.toFixed(83); | Null check. | TypeScript |
if (x = 46) | if (x == 46) | Use ==. | C++ |
val b: Int = 'data' | val b: String = 'data' | Fix type. | Kotlin |
{{"name":"data" "name":61}} | {{"name":"data", "name":61}} | Add comma. | JSON |
let msg = String::from("value"); let borrow=&msg; msg.push_str("!"); | let mut msg = String::from("value"); let borrow=&msg; println!("{{}}", borrow); msg.push_str("!"); | Cannot mutate while borrowed. | Rust |
WHERE status = '30' | WHERE status = 30 | Don't quote integer. | SQL |
["data", 16] | ["data", 16] | Correct. | JSON |
<br></br> | <br> | Self-closing. | HTML |
if result > 35
print('info') | if result > 35:
print('info') | Colon missing after if. | Python |
arr.forEach(function(a) {{ console.log(a); }}) | arr.forEach((a) => {{ console.log(a); }}) | Arrow functions are cleaner. | JavaScript |
let list=vec![67,34,3]; let head=&list[0]; list.push(93); | let mut list=vec![67,34,3]; let head=list[0]; list.push(93); | Copy instead of reference. | Rust |
Write-Host 'message' | Write-Host 'message' | Correct. | PowerShell |
let num: Int = 'result' | let num: String = 'result' | Fix type. | Swift |
'70' + 20 | 70 + 20 | Avoid string coercion. | JavaScript |
<root><child>text</child></root> | <root><child>text</child></root> | Correct. | XML |
function test() {{
return
{{key:'test'}}
}} | function test() {{
return {{key:'test'}};
}} | Return object on same line. | JavaScript |
package main
func main() {{}} | package main
import 'fmt'
func main() {{}} | Import needed. | Go |
$b = 53; if ($b = 53) {{}} | $b = 53; if ($b == 53) {{}} | Use ==. | PHP |
let mut result=12; let r1=&mut result; let r2=&mut result; | let mut result=12; {{ let r1=&mut result; }} let r2=&mut result; | Only one mutable borrow. | Rust |
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