English An or A?

Question

Given a string consisting of only upper and lower case letters, output an if it begins with a vowel, and a if not. For the purposes of this challenge, we'll ignore normal grammar rules, and use a very basic rule instead: if the input begins with a vowel (any of AEIOUaeiou), then output an. Otherwise, output a.

Your program should be case insensitive (computer and CoMpUtER are the same). This is code-golf, so the shortest code in bytes wins

Test cases

airplane: an
water: a
snake: a
hybrid: a
igloo: an
WATER: a
IglOO: an
HoUr: a
unIverSe: an
youTH: a

Note that for the last 3, they contradict typical grammar rules, in favour of our simplified rule, and that y is not counted as a vowel

Answer 1

C (gcc), 44 bytes

f(int*s){printf("a%.*s",2130466>>*s&1,"n");}

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Commented

f(int *s) {     // *s = input string
  printf(       // print ...
    "a%.*s",    //   the letter 'a' followed by a string with
                //   a dynamic length
    2130466     //   using the bitmask of vowels:
                //     1000001000001000100010
                //     ^     ^     ^   ^   ^
                //     utsrqponmlkjihgfedcba_
    >> *s & 1,  //   output 1 character if the first character
                //   is a vowel, or zero otherwise
                //   (assumes that the shift is modulo 32,
                //   which is guaranteed on Intel and may be
                //   true on ARM as well)
    "n"         //   where the string to be printed is "n"
  );            //
}               //

---

C (clang), 39 bytes

This version was suggested by Johan du Toit.

f(*s){write(1,"an",(2130466>>*s&1)+1);}

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---

C (clang), 36 bytes

This one was suggested by dingledooper.

f(*s){puts(2130466>>*s&1?"an":"a");}

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Answer 2

Factor + english, 15 bytes

[ >lower a/an ]

Almost a builtin. For whatever reason, a/an doesn't handle capital letters properly so we need to make it lowercase first. Luckily it's simplistic enough that it doesn't return the correct article for 'universe.'

Doesn't work on TIO because the english vocabulary postdates build 1525 (the one TIO uses), so have a picture:

Answer 3

Japt v2.0a0 -mg, 9 8 bytes

Takes input as an array of characters.

è\v îÍia

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è\v çÍia     :Implicit map of each element in input array
è            :Count the occurrences of
 \v          :  RegEx /[aeiou]/gi
    ç        :Repeat that many times
     Í       :  "n"
      ia     :Prepend "a"
             :Implicit output of first element

The Í is Japt's shortcut for n2<space> (Mainly intended for converting binary strings to decimal) The space close the ç method and the n and the 2 are passed to it as individual arguments but as ç only expects one argument the 2 is ignored.

Answer 4

Python 3, 37 bytes

lambda x:'a'+'n'*(x[0]in'aeiouAEIOU')

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-1 thanks to @xnor

Answer 5

JavaScript, 32 31 bytes

-1 thanks to @Arnauld

s=>/^[aeiou]/i.test(s)?"an":"a"

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Answer 6

jq, 36 bytes

1?*(test("^[aeiou]";"i")//"a")//"an"

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Some longer alternatives:

"an"[:match("^[aeiou]?";"i").length+1]

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.[:1]|1?*(inside("aeiouAEIOU")//"a")//"an"

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"a"+sub("^([^aeiou](?<x>))?.*";.x//"n";"i")

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Answer 7

Vyxal r, 11 9 bytes

hk∨c›‛anẎ

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hk∨c›‛anẎ
h          - First character of input
 k∨       - All vowels ("aeiouAEIOU")
    c      - A in B? ("h" in "k∨"?)
     ›     - Increment
      `an  - Two-byte string literal "an"
         Ẏ - Slice until B (A[0:B])

9 bytes thanks to @Aaron Miller

Answer 8

Dyalog APL, 21 chars

'an'↑⍨1+'aeiou'∊⍨⊃∘⎕c

Same logic as this Jelly answer. This answer feels too long...

Answer 9

PowerShell Core, 33 bytes

"a"+"n"*("$args"-match"^[AEIOU]")

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Or 36 bytes without regex

"a"+"n"*($args[0]-in("AEIOU"|% t*y))

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Answer 10

PHP, 36 34 bytes

fn($s)=>stripos(_aeiou,$s[0])?an:a

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Straightforward PHP code. Ignoring accented vowels of course, the _ is ignored, it is only there so that the index in the string is truthy

EDIT: saved 2 bytes thanks to YetiCGN's suggestions

Answer 11

Perl 5 -p, 28 20 bytes

27 bytes for the actual code; +1 byte for -E to get say

-8 bytes by golfing further

$_=/^[aeiou]/i?an:a

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Answer 12

JavaScript, 91 73 bytes

-18 from @emanresuA

a=(s)=>{return 'a'+('AEIOU'.includes(s.charAt(0).toUpperCase())?"n":"");}

Explanation

a=                        declares variable
(s)=>{                    ES6 Arrow Function
return 'a'+               return statement
('AEIOU'.includes(        check if in string 'AEIOU'
s.charAt(0)               first letter of string
.toUpperCase())           case insensitivity
?                         ternary operator
"n"                       if true, add 'n'  (an)
:"");                     else, add nothing (a)
}                         finish function

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Old TIO link

first time here so let me know if I missed something

Answer 13

Scratch, 69 bytes

Run it here

(The executing script does not need to be counted. Look inside and find the custom block for the code)

define(x
say(join[a](letter<[aeiouAEIOU]contains(letter(1)of(x))>of[n

Answer 14

Jelly, 9 bytes

ḢeØc‘⁾anḣ

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The footer simply extracts the test case from the : separated string

How it works

ḢeØc‘⁾anḣ - Main link. Takes a string S on the left
Ḣ          - Extract the first character of S
  Øc       - Yield vowels; "AEIOUaeiou"
 e         - Is the first character in that string? Yield 1 if so, else 0
    ‘      - Increment, yielding 2 for vowel-starting strings, 1 otherwise
      ⁾anḣ - Take that many characters of the string ⁾an

Answer 15

TI-Basic, 43 bytes

Input Str1
"a
If inString("AEIOUaeiou",sub(Str1,1,1
"an

Ouput is stored in Ans.

Answer 16

R, 47 bytes

function(s)"if"(grepl("^[aeiou]",s,T),"an","a")

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Other solutions:

function(s)c("a","an")[1+grepl("^[aeiou]",s,T)]   # 47 bytes
function(s)paste0("a","n"[grepl("^[aeiou]",s,T)]) # 49 bytes

Answer 17

Nim, 61 bytes

proc a(i:string):string=
 if i[0]in "aeiouAEIOU":"an"else:"a"

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Simple explanation + ungolfed code:

# Define function
proc a(i: string): string =
 # If the first character of 'i' is in "aeiouAEIOU",
 # Then it is a "an"
 if i[0] in "aeiouAEIOU":
  return "an"
 # Else, return "a"
 else:
  return "a"

Answer 18

Java (JDK), 39 bytes

s->s.matches("(?i)^[aeiou].*")?"an":"a"

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Answer 19

05AB1E, 12 11 bytes

„anžMIнlå>∍

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Explanation:

„an          # Push "an"
   žM        # Push builtin constant "aeiou"
     I       # Push the input-string
      н      # Pop and leave just its first character
       l     # Convert it to lowercase
        å    # Check if this lowercase first letter is in the vowels-string
         >   # Increase it by 1
          ∍  # Shorten the "an" to this length
             # (after which the result is output implicitly)

Answer 20

Haskell, 80 76 74 64 40 35 bytes

-24 thanks to @Franky
-5 thanks to @ovs

a(x:_)='a':['n'|elem x"aeiouAEIOU"]

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Answer 21

F#, 61 bytes

let a(i:string)=if"aeiouAEIOU".Contains(i.[0])then"an"else"a"

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Alternative 66 bytes solution:

let a(i:string)=if"aeiouAEIOU".Contains(i.Chars(0))then"an"else"a"

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Check if the input's first character is in aeiouAEIOU or not (if"aeiouAEIOU".Contains(i.Chars(0))), if true, return "an" (then"an"), else, return "a" (else"a")

Ungolfed version:

let anOrA (inpt : string) =
 if "aeiouAEIOU".Contains(inpt.Chars(0)) then "an" else "a"

Answer 22

Vim, 20 bytes

lD:s/[aeiou]\c/an
ra

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Explanation:

lD                 # Keep only the first character
  :s/[aeiou]\c/an  # Replace any of AEIOUaeiou with 'an'
ra                 # Replace the first character with 'a'

Answer 23

C (clang), 34 bytes

f(*s){puts("a\00an"+('A\04D'>>*s&2));}

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Partial based on dingledooper's answer.

\00 and \04 should be replaced by raw bytes instead of using escaped character sequences.

Answer 24

JavaScript (ES6), 37 bytes

s=>'a'+(/[aeiou]/i.test(s[0])?"n":"")

Answer 25

Python, 42 37 bytes

lambda s:'a'+'n'*(2130466>>s[0]%32&1)

Uses the same logic as this C answer, but I have to take %32 because python bit shifts aren't modulo 32.

Note that I take advantage of order of operations by using %32 and &1 (which is %2) to avoid needing parentheses.

(-5): Removed the ord() by taking a bytestring (bytes) instead of a str.

Answer 26

jq, 33 bytes

(match("^[aeiou]";"i")|"an")//"a"

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Answer 27

Zsh --continue-on-error, 25 bytes

>$1:l
s=n<[aeiou]*
<<<a$s

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When [aeiou]* fails to match (i.e., the word begins with a consonant), Zsh would normally exit with a "fatal" error. The aptly named option CONTINUE_ON_ERROR overrides this, and simply skips the assignment line s=n instead.

Answer 28

International Phonetic Esoteric Language, 40 bytes

0h"aeiouAEIOU"dʔdpʌɔ|a|"an"ɔ|e||a|"a"|e|

Expects a string, leaves the string and a "a" or "an".

Ungolfed:

               (s -- a/an)
0h             (first char)
"aeiouAEIOU"dʔ (is c a vowel?)
dp             (discard vowels)
ʌɔ|a|          (if c is not a vowel, go to |a|)
|an|"an"ɔ|end| (when c is a vowel)
|a|"a"         (when c is not a vowel)
|end|

Answer 29

GAIA, 32 bytes

{(⟨₵v&!!⟩⟨₵V&!!⟩v}⟨“a”p⟩⟨“an”p⟩?

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Probably could be shortened, especially on the second section.

Explanation:

( -takes first letter of the input

₵v& - is member (&) of string aeiou (₵v) -> returns the contained letter if member, empty if not.

₵V& - is member (&) of string AEIOU (₵V) -> returns the contained letter if member, empty if not.

!! - if the passed value is empty returns 0, otherwise 1

v - is logical or

{(⟨₵v&!!⟩⟨₵V&!!⟩v} - so this checks if the first letter is member of either lower or upper case vowels

⟨“a”p⟩⟨“an”p⟩? - this checks for the value passed by the first section, if true executes the first member, if false the second.

p -prints a string

Answer 30

K (ngn/k), 21 bytes

Solution:

{$`an`a@^"aeiou"?*_x}

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Explanation:

{                   } / function taking implicit x argument
                  _x  / convert x to lowercase
                 *    / take first
         "aeiou"?     / find right in left
        ^             / null?
  `an`a@              / index into 2-item list (`a;`an)
 $                    / convert to string