Shortest code to check if a string has only letters [closed]

Question

Your task is to create a program which takes a string, and if it contains any numbers, symbols or other non-letter characters, it throws an error. Else, it returns the original string. (The string may include whitespace)

("Letters" are a-z and A-Z)

Examples:

Input: My name is Joe

Output My name is Joe

---

Input: My username is Joe32

Output: (insert an error)

(FYI this question has nothing to do with Don't Google google. It was identified as a possible copy.)

Answer 1

Julia, 53 bytes

s=readline();ismatch(r"[^a-z\s]"i,s)?error():print(s)

Read a string from STDIN using readline(). If any of its characters are not letters or whitespace (ismatch(r"[^a-z\s]"i, s)) then we error(), otherwise we print(s).

Answer 2

Gema, 14 characters

\W<-L>=@div{;}

Sample run:

bash-4.3$ gema '\W<-L>=@div{;}' <<< 'My name is Joe'
My name is Joe

bash-4.3$ gema '\W<-L>=@div{;}' <<< 'My username is Joe32'
Floating point exception (core dumped)

Answer 3

Python 3, 56 characters

import re;print(re.match(r'[a-z\s]+$',input(),2).string)

Usefully, match objects have this attribute string which is

The string passed to match() or search().

while None does not.

In [10]: import re;print(re.match(r'[a-z\s]+$',input(),2).string)
54
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-10-0851dec671d1> in <module>()
----> 1 import re;print(re.match(r'[a-z\s]+$',input(),2).string)

AttributeError: 'NoneType' object has no attribute 'string'

In [11]: import re;print(re.match(r'[a-z\s]+$',input(),2).string)
rffef 
rffef 

Answer 4

PowerShell, 24 bytes

Filter the pipeline input based on whether it matches the regex:

|?{$_-match'^[a-z\s]+$'}

e.g. try it by piping the string in:

PS C:\> "Test Test"|?{$_-match'^[a-z\s]+$'}
Test Test

PS C:\> "Test ! Test"|?{$_-match'^[a-z\s]+$'}

The error message is silence/empty result. It matches case-insensitively by default.

Answer 5

C++14, 132 126 121 117 121 bytes

#include<iostream>
main(){std::string s;getline(std::cin,s);for(char c:s)if(!isalpha(c)&!isspace(c))throw;std::cout<<s;}

We read a line from stdin, check if each character is a letter or space - if it's not, we throw an error. Finally outputs the input.

Thanks to Alex A for golfing off two bytes

Answer 6

STATA, 57 bytes

di _r(a)
gl b=1/regexm("$a","^[a-zA-Z ]*$")
di _d($b)"$a"

Uses a regex to match letters and space (STATA's regex doesn't include character classes). Set a variable to 1/match exists. Then it prints a that many times, if match exists=0, it says it's invalid syntax. Otherwise, it prints it 1/1 = 1 time.

Answer 7

CJam, 18 bytes

q_"  
"'[,_el^|-!/

The multi-line string contains a tabulator, a space and a linefeed.

Try it online in the CJam interpreter.

How it works

q_                    Read all input from STDIN and push a copy.
  "\t \n"             Push that string.
         '[,_el^      Push all letters. See: codegolf.stackexchange.com/a/54348
                |     Concatenate both strings.
                 -    Remove their characters from the copy of the input.
                  !   Logical NOT. Pushes 0 if there are other characters.
                   /  Split. Doesn't affect output if successful. Errors on 0.

Answer 8

Haskell, 56 bytes

q x|all(`elem`(['a'..'z']++['A'..'Z']++['\t'..'\r']))x=x

Throws the Non-exhaustive patterns in function q error if the string contains forbidden characters.

Answer 9

JavaScript, 48 46 45 46 31 Bytes

/[^a-z\s]/i.exec(a=prompt())?q:a

Accepts input, searches for invalid characters, if it finds any, returns a truthy value and thus evaluates the undefined character q. Otherwise, returns null and thus returns the string.

Old version, 44 bytes

~(a=prompt()).search(/[^a-z\s]/i)?eval("@"):a

Tries to evaluate the invalid character @ upon finding a numeric.

---

Edit 1: -2 bytes, thanks to @Alex A.

Edit 2: -1 byte, reworked. BONUS: Accounts for ALL whitespace! ^_^

Edit 3: +1 byte, added underscore testing.

Edit 4: Back to 46, unreworked.

Edit 5: -2 extra bytes to @edc65 (for old version; -1 for new).

Answer 10

Python 2, 60 bytes

import re;n=input();print[n][re.sub('[^a-zA-Z\s]+','',n)!=n]

Usage:

$ python -c "import re;n=input();print[n][re.sub('[^a-zA-Z\s]+','',n)!=n]"
"abcdefg"
abcdefg

Answer 11

Hassium, 166 Bytes

func main(){r="";foreach(c in input()){c=c.toString();if(!("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ \t\n\r".contains(c)))throw(c);else r+=c;}println(r);}

Run and see expanded here

Answer 12

PHP, 51 48 bytes

<?=preg_match('/[^a-z\s]/i',$a=$argv[1])?e():$a;

Runs from command line, like:

php test.php "Test me"

---

Using preg_match is shorter than using ctype_alpha as the latter needs whitespaces to be stripped.

---

As the error wasn't defined in the challenge, calling an undefined function seems the shortest way to generate an error. So this:

php test.php "Test me, 2"

leads to:

PHP Fatal error: Call to undefined function e()

Edit

Saved 3 bytes by inverting the statement an by using the i-modifier. Thanks to fschmengler.

Answer 13

Stax, 8 bytes

êF┼Aµ╧û┤

Run and debug online!

Shortest solution so far but expect to be defeated soon.

Explanation

Uses the unpacked version to explain.

' Vl+-!uy
' Vl+        Alphabet plus space
     -       Remove from input
      !u     If result is not empty raise division by zero error
        y    Else print input

Answer 14

Python 2, 68 71 70 69 bytes

import re;s=raw_input();print s if re.match(r'[a-z\s]+$',s,2)else 0/0

Thanks to Alex A. and Martin Büttner for saving a byte and NightShadeQueen for another byte!

Answer 15

Java 127 Bytes

class A{public static void main(String[]a){String s=System.console().readLine();System.out.print(s.matches("[A-z ]+")?s:0/0);}}

In Java from the command line you can have input and with the help of regular expression [A-z ]+ which matches alphabets and space in the line, you can have this kind of trick.Moreover, 0/0 will throw ArithmeticException.

Answer 16

C# - 174 157 148 bytes

using System.Linq;namespace System{class A{static void Main(string[]s){if(!s[0].All(char.IsLetter))throw new Exception();Console.WriteLine(s[0]);}}}

usage:

Console application that takes a parameter in the form of a string and checks via LINQ if all the characters in that string are letters. If so, writes it to console. Otherwise throws exception.

Not particularly short. Will keep tinkering!

Edit: Think I'm pretty much done. Can't get it much shorter don't think.

Answer 17

Ruby, 26 25 bytes

"undefined method `+@' for nil:NilClass (NoMethodError)":

+(gets=~/^[A-z]*$/);print

Previous 26 bytes, "in `/': divided by 0 (ZeroDivisionError)":

puts gets[/^[A-z]*$/]||1/0