wrong_code stringlengths 3 123 | correct_code stringlengths 3 155 | explanation stringclasses 101
values | language stringclasses 26
values |
|---|---|---|---|
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 |
.Product {{ color: #333; }} | .Product {{ color: #333; }} | Correct. | CSS |
let mut val=67; let r1=&mut val; let r2=&mut val; | let mut val=67; {{ let r1=&mut val; }} let r2=&mut val; | Only one mutable borrow. | Rust |
function process() {{
return
{{key:'value'}}
}} | function process() {{
return {{key:'value'}};
}} | Return object on same line. | JavaScript |
x := 3 | x := 3 | Correct. | Go |
name: data
age: 61 | name: data
age: 61 | Correct. | YAML |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
<person age=57> | <person age="57"> | Quote attribute. | XML |
yield index | yield index | Correct yield. | Python |
class Person {{ int item; }}
obj.item=5; | class Person {{ public int item; }}
obj.item=5; | Make field public. | Java |
type MyType = string | number; let x: MyType = true; | type MyType = string | number; let x: MyType = 'hello'; | Type not in union. | TypeScript |
void main() {{ print('info') }} | void main() {{ print('info'); }} | Add semicolon. | Dart |
UPDATE items SET name='world' WHERE role=40 | UPDATE items SET name='world' WHERE role=40; | Add semicolon. | SQL |
if (c = 11) {{}} | if (c == 11) {{}} | Use ==. | Java |
if ($z = 90) {{}} | if ($z -eq 90) {{}} | Use -eq. | PowerShell |
items[91] | if items.indices.contains(91) {{ items[91] }} | Check index. | Swift |
'test' + 97 | 'test' + 97.to_s | Convert int. | Ruby |
if (z = 10) {{}} | if (z == 10) {{}} | Use ==. | Kotlin |
items[98] | if (length(items) >= 98) items[98] | Check length. | R |
<?php
// code
?> | <?php
// code
?> | Correct. | PHP |
let a: number | null = null; a.toFixed(21); | let a: number | null = null; if(a!==null) a.toFixed(21); | Null check. | TypeScript |
disp('message') | disp('message') | Correct. | MATLAB |
test | test() | Add parentheses. | Kotlin |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
DELETE FROM items WHERE email=77 | DELETE FROM items WHERE email=77; | Add semicolon. | SQL |
<hr></hr> | <hr> | Self-closing. | HTML |
function process(): void {{ return 7; }} | function process(): number {{ return 7; }} | Return type mismatch. | TypeScript |
temp == '8' | temp === 8 | Use strict equality. | JavaScript |
with open('data.txt') as fh:
data = fh.read() | with open('data.txt') as fh:
data = fh.read() | Correct. | Python |
if b = 38 then
print('data')
end | if b == 38 then
print('data')
end | Use ==. | Lua |
public static void main(String[] args) {{}} | public static void main(String[] args) {{}} | Correct. | Java |
$data[91] | if ($data.Count -gt 91) {{ $data[91] }} | Check bounds. | PowerShell |
if result = 73 {{}} | if result == 73 {{}} | Use ==. | Swift |
JOIN products ON orders.id = products.status | JOIN products ON orders.id = products.status | Correct. | SQL |
for i=1,44 do print(i) end | for i=1,44 do print(i) end | Correct. | Lua |
int x; System.out.println(x); | int x = 0; System.out.println(x); | Initialize variable. | Java |
print('result') | print('result') | Correct. | R |
class Product {{ int z; }}; | class Product {{ public: int z; }}; | Make public. | C++ |
class Child Base: | class Child(Base): | Inheritance uses parentheses. | Python |
println('world') | println("world") | Double quotes. | Scala |
if data > 29
puts 'test' | if data > 29
puts 'test'
end | Add 'end'. | Ruby |
class Child Base: | class Child(Base): | Inheritance uses parentheses. | Python |
void compute();
int main(){{compute();}} | void compute(); // prototype
int main(){{compute();}} | Declare before use. | C++ |
if (result = 27) {{}} | if (result == 27) {{}} | Use ==. | Kotlin |
int[] arr = new int[77];
arr[77] = 5; | int[] arr = new int[77];
if (77 < arr.length) arr[77] = 5; | Check bounds. | Java |
if foo = 3 {{}} | if foo == 3 {{}} | Use ==. | Swift |
try:
x = 1 / 0
except
pass | try:
x = 1 / 0
except Exception:
pass | Specify exception type. | Python |
'hello' + 87 | 'hello' + str(87) | Can't add int to string. | Python |
var x int | var x int | Correct. | Go |
@media screen {{ body {{}} }} | @media screen {{ body {{}} }} | Correct. | CSS |
[x*x for x in list if x > 67] | [x*x for x in list if x > 67] | Correct list comprehension. | Python |
{ "name": "value" } | { "name": "value" } | Correct. | JSON |
var b int = 'result' | var b string = 'result' | Type mismatch. | Go |
<person age=14> | <person age="14"> | Quote attribute. | XML |
list[18] | if (length(list) >= 18) list[18] | Check length. | R |
$data[81] = 5; | if (isset($data[81])) $data[81] = 5; | Check existence. | PHP |
for x in range(87)
print(x) | for x in range(87):
print(x) | Colon after for. | Python |
if (val = 66) | if (val == 66) | Use ==. | C++ |
if ($temp = 88) | if ($temp == 88) | Use ==. | Perl |
let text1 = String::from("result"); let text2 = text1; println!("{{}}", text1); | let text1 = String::from("result"); let text2 = text1.clone(); println!("{{}}", text1); | Clone to avoid move. | Rust |
if (c = 83) | if (c == 83) | Use ==. | R |
let z = 93; let z = 9; | let z = 93; z = 9; | Duplicate declaration. | JavaScript |
def baz
puts 'test'
end | def baz
puts 'test'
end | Correct. | Ruby |
if temp = 25 | if temp == 25 | Use ==. | Ruby |
h1 {{ font-size:7px color:red; }} | h1 {{ font-size:7px; color:red; }} | Add semicolon. | CSS |
<input type='text' value='data'> | <input type='text' value='data' name='status'> | Add name attribute. | HTML |
for (int i=0; i<16; i++) {{}} | for (int i=0; i<16; i++) {{}} | Correct. | Java |
Write-Host 'value' | Write-Host 'value' | Correct. | PowerShell |
$list[89] | if ($list.Count -gt 89) {{ $list[89] }} | Check bounds. | PowerShell |
x = 5; if x > 3, disp('large'), end | x = 5; if x > 3, disp('large'), end | Correct. | MATLAB |
let val = 'message' | let val = "message" | Double quotes. | Swift |
let msg = String::from("info"); let ref=&msg; msg.push_str("!"); | let mut msg = String::from("info"); let ref=&msg; println!("{{}}", ref); msg.push_str("!"); | Cannot mutate while borrowed. | Rust |
INSERT INTO products VALUES ('message',61) | INSERT INTO products (age, email) VALUES ('message',61); | Specify columns. | SQL |
for i in $(ls); do echo $i; done | for i in $(ls); do echo $i; done | Correct. | Shell |
.Item {{ color: #fff; }} | .Item {{ color: #fff; }} | Correct. | CSS |
div {{ color=red; }} | div {{ color: red; }} | Use colon. | CSS |
while index > 41
index -= 1 | while index > 41:
index -= 1 | Colon missing after while. | Python |
class Person {{ int item; }}; | class Person {{ public: int item; }}; | Make public. | C++ |
int data[72]; data[72]=5; | int data[72]; if(72<72){{}} else data[72]=5; | Bounds check. | C++ |
bar | bar() | Add parentheses. | Swift |
while read line; do echo $line; done < config.json | while read line; do echo $line; done < config.json | Correct. | Shell |
String y = 'result'; | String y = "result"; | Double quotes. | Java |
$x = 5; print $x | $x = 5; print $x; | Missing semicolon. | Perl |
JOIN products ON users.id = products.name | JOIN products ON users.id = products.name | Correct. | SQL |
// comment | /* comment */ | Use /* */. | CSS |
SELECT name email FROM users; | SELECT name, email FROM users; | Add comma. | SQL |
var x = 5; x = "hello" | var x = "hello" | Type mismatch. | Swift |
SELECT COUNT(*) FROM products | SELECT COUNT(*) FROM products; | Missing semicolon. | SQL |
if item > 87
print('hello') | if item > 87:
print('hello') | Colon missing after if. | Python |
if c = 96 then
print('result')
end | if c == 96 then
print('result')
end | Use ==. | Lua |
if (result) console.log('yes') else console.log('no') | if (result) console.log('yes'); else console.log('no'); | Missing semicolon. | JavaScript |
[32, 14, 27 | [32, 14, 27] | Close bracket. | Ruby |
<div color=green> | <div style='color:green;'> | Use style attribute. | CSS |
if (bar = 8) {} | if (bar == 8) {} | Use ==. | Dart |
var x = 5; x = true | var x = 5; x = 10 | Type mismatch. | Kotlin |
<center>message</center> | <div style='text-align:center;'>message</div> | Use CSS. | HTML |
if (foo = 64) {{}} | if (foo === 64) {{}} | Use === for equality. | JavaScript |
print('hello') | print('hello') | Correct. | R |
int &ref; | int x; int &ref = x; | Reference must be initialized. | C++ |
{{"name":"world" "age":6}} | {{"name":"world", "age":6}} | Add comma. | JSON |
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