Converting a string to lower-case (without built-in to-lower functions!)

Question

The goal of this code-golf is to create a code that lets the user input an ASCII string (contains only printable ASCII characters), and your program outputs the lower-case variant of this string.

Important: you are NOT allowed to use a built-in function that converts the string (or just one character) to lowercase (such as ToLower() in .NET, strtolower() in PHP , ...)! You're allowed to use all other built-in functions, however.

Another important note: The input string doesn't contain only uppercase characters. The input string is a mix of uppercase characters, lowercase characters, numbers and other ASCII printable characters.

Good luck!

Answer 1

Shell - 10

Translation of @Gowtham's Perl solution using /bin/tr.

tr A-Z a-z

Sample run:

% tr A-Z a-z <<<'Hello WORLD! @'
hello world! @

Answer 2

Python 2.7 - 30 (with terrible and unapologetic rule abuse)

raw_input().upper().swapcase()

As an anonymous edit pointed out, you can do it in 27 26 in Python 3:

input().upper().swapcase()

I'm flagrantly abusing the rules here, but...

Important: you are NOT allowed to use a built-in function that converts the string (or just one character) to lowercase (such as ToLower() in .NET, strtolower() in PHP , ...)! You're allowed to use all other built-in functions, however.

This takes the strings and coverts it to upper case. Then in a very unrelated method call, it reverses the case of the string - so that any lower case letters become upper case letters... and swaps any upper case letters to lower case letters.

Answer 3

Perl - 11 10 characters.

y/A-Z/a-z/

y/// is same as tr///!

In action:

% perl -pe 'y/A-Z/a-z/' <<< 'Hello @ WORLD !'
hello @ world !

Answer 4

Befunge-98 - 26 22 21 19

~:''-d2*/1-!' *+,#@

Relies on the fact that (c-39)/26 is 1 only for character codes of uppercase ASCII characters (assuming integer division). For each character c, print out c + (((c-39)/26)==1)*' '.

Sample session:

% cfunge lower.b98
hello WORLD!
hello world!
This is a TEST!!11 az AZ @[`{
this is a test!!11 az az @[`{

Answer 5

Python 3, 58

print("".join(chr(ord(x)+('@'<x<'[')*32)for x in input()))

Answer 6

Ruby, 18 characters

Nothing really interesting.

gets.tr'A-Z','a-z'

(run in IRB)

Just for fun: a confusing version:

$,=$* *' ';$;=$,.tr'A-Z','a-z';$><<$;

Run like this:

c:\a\ruby>lowercase.rb Llamas are AMAZING!

Output

llamas are amazing!

Answer 7

J - 30

'@Z'(]+32*1=I.)&.(a.&i.)1!:1]1

J is read right-to-left, so to break this down:

1. Prompt user for input: 1!:1]1
2. Perform algorithm in code-point-space: &.(a.&i.)
3. Identify character range for each letter; the characters between codepoints "@" and "Z" are considered uppercase: 1=I..
4. For each uppercase codepoint, add 32: ]+32* ...
5. Note that step (2) creates an implicit step (5): we started out by projecting from character to integer domain, so now that we're finished, we map those integers back onto characters.

Obviously this particular implementation only considers ASCII; but the approach could be extended to at least the basic multilingual plane in Unicode.

Answer 8

C 64 63 59 55 chars

main(c){while(c=getchar(),~c)putchar(c-65u<27?c+32:c);}

Answer 9

Golfscript - 17

Program:

{..64>\91<*32*+}%

Explanation:

1. {}% maps the code inside to every character in string.
2. .. copies the top of the stack (the character) twice.
3. 64> 1 if character code is greater than 64, else 0.
4. \ swaps the two items on the stack (gets the second copy of the letter, and stores the result of 64> in position two).
5. 91< checks to see if character code is less than 91. Similar to step 3.
6. * multiplies the results from steps 3 and 5 together. Only equal to 1, if both steps were true.
7. 32* multiplies the result of step 6 with 32. Will be 32 if step 6 was 1, else 0.
8. + add the result (either 32 or 0) onto the character code.

Example output:

echo HelLO @ WorLD | ruby golfscript.rb upper_to_lower.gs
hello @ world

Answer 10

Perl: 24 characters

s/[A-Z]/chr 32+ord$&/ge

Sample run:

bash-4.1$ perl -pe 's/[A-Z]/chr 32+ord$&/ge' <<< 'Hello @ WORLD !'
hello @ world !

Answer 11

javascript 80

"X".replace(/[A-Z]/g,function($){return String.fromCharCode($.charCodeAt()+32)})

(76 if you remove "X")

with prompt and alert - 92

alert(prompt().replace(/[A-Z]/g,function($){return String.fromCharCode($.charCodeAt()+32)}))

fiddle

thanks to @FireFly @some @C5H8NNaO4 and @minitech

Answer 12

JavaScript - 109 104 (ES6: 95)

Thanks to some for the corrected version.

a=prompt();for(b=[i=0];c=a.charCodeAt(i);)b[i++]=String.fromCharCode(c|(c>64&c<91)*32);alert(b.join(""))

The following works if the browser supports ES6 function expressions:

alert(prompt().split("").map(c=>String.fromCharCode(c.charCodeAt()|(c>"@"&c<"[")*32)).join(""))

Answer 13

DELPHI

const
  UpChars:set of AnsiChar = ['A'..'Z'];
var
  I: Integer;
begin
  SetLength(Result, Length(pString));
  for I := 1 to length(pstring) do
    Result[i] := AnsiChar((Integer(pString[i] in UpChars))*(Ord(pString[i])+32));
  WriteLn(Result);
end;

Answer 14

Python (33)

If in doubt, use the shell.

import os;os.system('tr A-Z a-z')

Regrettably, this is still longer than Lego's solution.

Answer 15

Perl 18

s/[A-Z]/$&|" "/eg

Something like:

perl -pe 's/[A-Z]/$&|" "/eg'  <<<'are NOT allowed to: ToLower() in .NET, strtolower() in PHP'
are not allowed to: tolower() in .net, strtolower() in php

and

perl -pe 's/[A-Z]/$&|" "/eg' <<< "The input string Doesn't cOntaIn...( C0D3-@01F. ;-)"
the input string doesn't contain...( c0d3-@01f. ;-)

For @FireFly :

perl -pe 's/[A-Z]/$&|" "/eg' <<< "Doesn't this translate @ to \` and [\]^_ to {|}~DEL? "
doesn't ... @ to ` and [\]^_ to {|}~del? 

no.

More generic: 18 chars anyway:

s/[A-Z]/$&|" "/eg

s/[A-Z]/$&^" "/eg

This wont change anything in state:

perl -pe 's/[A-Z]/$&^" "/eg' <<< "Doesn't ... @ to \` and [\]^_ to {|}~DEL? "
doesn't ... @ to ` and [\]^_ to {|}~del? 

All work fine, but the advantage of changing | (or) by ^ (xor) is that the same syntax could be used for toLower, toUpper or swapCase:

toUpper:

perl -pe 's/[a-z]/$&^" "/eg' <<< "Doesn't ... @ to \` and [\]^_ to {|}~DEL? "
DOESN'T ... @ TO ` AND [\]^_ TO {|}~DEL? 

and swapCase (18+1 = 19 chars):

perl -pe 's/[a-z]/$&^" "/egi' <<< "Doesn't ... @ to \` and [\]^_ to {|}~DEL? "
dOESN'T ... @ TO ` AND [\]^_ TO {|}~del? 

Answer 16

R

71 characters:

chartr(paste(LETTERS,collapse=""),paste(letters,collapse=""),scan(,""))

83 characters:

a=as.integer(charToRaw(scan(,"")))
b=a%in%(65:90)
a[b]=a[b]+32
rawToChar(as.raw(a))

Answer 17

Q, 18

.....

{x^ssr/[x]..Q`a`A}

Answer 18

PHP (42)

Run from the command line:

-R'echo@str_ireplace($a=range(a,z),$a,$argn);'

-R and the single quotes are not counted.

Answer 19

Q (16)

.......

{x^(.Q.A!.Q.a)x}

Answer 20

PowerShell: 69 65 64

I've tried a half-dozen ways to get Replace to work the way I want it to without using the long [regex]::Replace syntax, but I haven't had any luck. If anyone else has an idea of what might work, please do suggest it.

Golfed code:

[regex]::Replace((read-host),"[A-Z]",{[char](32+[char]"$args")})

Changes from original:

• Rearranged last argument so that [int] is no longer needed, per suggestion in comments.

Explanation:

(read-host) gets the user input.

[regex]::Replace(...) tells PowerShell to use RegEx matching to perform replacement operations on a string.

"[A-Z]" matches all uppercase letters.

{...} tells PowerShell to use a script to determine the replacement value.

[char]"$args" takes the current match and types it as an ASCII character.

32+ converts the character to an integer, representing the ASCII code, and increases the value by 32 - which would match ASCII code of the corresponding lowercase letter.

[char](...) takes the resulting value and converts it back to an ASCII character.

Demo of original:

(Current version tested - screenshot not yet posted.)

Answer 21

PowerShell, 53 49 43 bytes

-4 bytes thanks @AdmBorkBork

-6 bytes thanks @Veskah

-join($args|%{[char](32*($_-in65..90)+$_)})

Try it online!

Answer 22

05AB1E, 3 bytes

u.š

Port of @user8777 Python 3 answer.

Try it online.

Explanation:

u    # Convert the (implicit) input to uppercase
 .š  # Switch the case (upper to lower and vice-versa)
     # (and output the result implicitly)

---

But without any case-altering builtins:

05AB1E, 12 11 bytes

ÇIS.u32*+çJ

-1 byte thanks to @Emigna.

Try it online.

Explanation:

Ç            # Get the unicode values of each character of the (implicit) input-String
 IS          # Get the input-string, split to characters again
   .u        # Check for each if it's uppercase or not (1 if truthy; 0 if falsey)
     32*     # Multiply that result by 32 (32 if truhy; 0 if falsey)
        +    # Add it to all the unicode values at the same indices in the list
         ç   # Convert the now modified unicode values back to characters
          J  # And join all characters together to a string again
             # (which is output implicitly as result)

Answer 23

k2, 15 bytes

I am super late to this one, but I found this cool anyway.

{_ci 32+_ic x}'

Also:

Pyth, 10 bytes

Doesn't really count because Pyth was created after this was posted. Still cool.

jkmC+32Cdw

Answer 24

Python 3 - 70

Updated for OP's changes.

I'm a Python newbie, so any critique is welcome.

print("".join(chr(ord(c)+32) if 64<ord(c)<91 else c for c in input()))

Answer 25

Javascript, 105

prompt().split("").map(function(a){c=a.charCodeAt(0);return String.fromCharCode(c|(c-64?32:0))}).join("")

_{Actually ther was no output form specified, so run it in console Yea, JavaScript really is verbose with charcode <-> string}

Answer 26

Ruby: 66

def l(s)s.bytes.map{|b|(65..90).include?(b)?b+32:b}.pack('c*');end

Answer 27

C# - 108

class P{static void Main(string[]a){foreach(var c in a[0])System.Console.Write(
(char)(c>64&&c<91?c+32:c));}}

About 70 for just the method body.

Add 5 chars to include a LF/CR in the output:

class P{static void Main(string[]a){foreach(var c in a[0]+"\n")System.Console.Write(
(char)(c>64&&c<91?c+32:c));}}

A LINQ version would be shorter:

class P{static void Main(string[]a){a[0].Any(c=>System.Console.Write(
(char)(c>64&&c<91?32+c:c))is P);}}

(103) .. except that it requires using System.Linq; (total: 121).

Answer 28

x86-16 machine code, 14 bytes

Assembled:

ac3c 417c 063c 5a7f 020c 20aa e2f2

Unassembled listing:

       _LOOP:
 AC         LODSB           ; load byte from [SI] into AL, advance SI 
 3C 41      CMP  AL, 'A'    ; is char less than 'A'? 
 7C 06      JL   _STORE     ; if so, do not convert 
 3C 5A      CMP  AL, 'Z'    ; is char greater than 'Z'? 
 7F 02      JG   _STORE     ; if so, do not convert 
 0C 20      OR   AL, 020H   ; lowercase the char 
       _STORE:
 AA         STOSB           ; store char to [DI], advance DI 
 E2 F2      LOOP _LOOP      ; continue loop through string 

Input string in [SI], length in CX. Output string in [DI].

Output from PC DOS test program:

Download and test TOLOW.COM example program.

Answer 29

naz, 92 bytes

2a2x1v4m8m2x2v2d3m5s2x3v1x1f1r3x1v4e3x2v2g1o1f0x1x2f3x3v3l1o1f0x1x3f8a8a8a8a1o1f0x1x4f0a0x1f

Works for any input string terminated with the control character STX (U+0002).

Explanation (with 0x commands removed)

2a2x1v                 # Set variable 1 equal to 2
4m8m2x2v               # Set variable 2 equal to 64 ("@")
2d3m5s2x3v             # Set variable 3 equal to 91 ("[")
1x1f1r3x1v4e3x2v2g1o1f # Function 1
                       # Read a byte of input
                       # Jump to function 4 if it equals variable 1
                       # Jump to function 2 if it's greater than variable 2
                       # Otherwise, output it and jump back to the start of function 1
1x2f3x3v3l1o1f         # Function 2
                       # Jump to function 3 if the register is less than variable 3
                       # Otherwise, output and jump to function 1
1x3f8a8a8a8a1o1f       # Function 3
                       # Add 32 to the value in the register, output, and jump to function 1
1x4f0a                 # Function 4
                       # Add 0 to the register
1f                     # Call function 1

Answer 30

Haskell - 58

p x|(elem x['A'..'Z'])=[x..]!!32|1<2=x
main=interact$map p

Answer 31

Perl, 9 + 1 (for -p flag) = 10

$_="\L$_"

\L was specifically asked about and allowed, because even though it's a built-in, it's not a function.

Answer 32

Just for fun, because Java's my language.

Java - 162 175

Fixed for OP's updates.

class a{public static void main(String[]a){String b="";for(char c:new java.util.Scanner(
System.in).nextLine().toCharArray())b+=c>64&&c<91?(char)(c+32):c;System.out.print(b);}}

With line breaks and tabs

class a{

    public static void main(String[]a){
        String b="";
        for(char c:new java.util.Scanner(System.in).nextLine().toCharArray())b+=c>64&&c<91?(char)(c+32):c;
        System.out.print(b);
    }

}

Answer 33

bash: 11 characters?

$ i="This is A STRING"
$ echo ${i,,}
this is a string

Answer 34

Python - 96 94 82

for c in input():print(chr(ord(c)-65+97),end="")if c.isupper()else print(c,end="")

Ungolfed version:

for char in input():
    print(chr(ord(char) - (ord("A") - ord("a"))), end="") if char.isupper() \
    else print(char, end="")

Answer 35

Because I felt like it (I know that I'm a bit late)

Java - 162

class a{public static void main(String[]a){for(char c:(new java.util.Scanner(System.in)).nextLine().toCharArray())System.out.print((char)((c>64&&c<91)?c+32:c));}}

expanded:

public class a{
    public static void main(String[] a) {
        for (char c : (new java.util.Scanner(System.in)).nextLine().toCharArray()) {
            System.out.print((char) ((c > 64 && c < 91) ? c + 32 : c));
        }
    }
}

Answer 36

Java - 119

class a{static{for(char c:(new java.util.Scanner(System.in)).nextLine().toCharArray())System.out.print((char)(c|32));}}

Works for every character except @ which becomes the back-tick (`), and the following (foo:bar for foo becomes bar) :

\:|
]:}
^:~
_:

Even though this isn't a true solution because it has 5 cases where it doesn't work, I thought it was very interesting. It takes the characters of the input and does a bitwise or with ' ' (c|32).

I discovered that c^32 swaps the case when the input is only letters while solving a project euler problem. I wondered what would happen in I changed the XOR to an OR.

Answer 37

Game Maker Language, 228

Make script/function s with this code, 53 characters:

a=argument0;b=string_replace_all(b,string_upper(a),a)

Then, use this 175 character code:

b=get_string('','')s('a')s('b')s('c')s('d')s('e')s('f')s('g')s('h')s('i')s('j')s('k')s('l')s('m')s('n')s('o')s('p')s('q')s('r')s('s')s('t')s('u')s('v')s('w')s('x')s('y')s('z')

The input (stored in variable b), is now lowercase.

Answer 38

JavaScript 124

The closest I got was 124 characters...

b=prompt();a=[];for(c=b.length;c--;)a[c]="@"<b[c]&"[">b[c]?String.fromCharCode(b[c].charCodeAt(0)+32):b[c];alert(a.join(""))

@Firefly, nice work with using the "map" command... I've yet to master it...

Answer 39

Japt v2.0a0, 7 bytes

r\A_c^H

Try it

Answer 40

q 37 bytes

{$[x in .Q.A;x:(.Q.A!.Q.a)[x];x]}each

Explanation

$[x in .Q.A          // If the character is in the capitals list
  x:(.Q.A!.Q.a)[x]   // Create a key mapping between upper and lower case letters,
                     // and set x to it's pair
  x]}                // else, just return the character
  each               // apply to each character in string passed in

Example

q){$[x in .Q.A;x:(.Q.A!.Q.a)[x];x]}each "LoWersWFSfdgSA"
"lowerswfsfdgsa"

Answer 41

JavaScript, 58 bytes

s=>s.replace(/[A-Z]/g,x=>(x.charCodeAt()-55).toString(36))

Answer 42

Forth (gforth), 55 bytes

: f 0 do dup i + c@ dup 65 91 within 32 * - emit loop ;

Try it online!

Explanation

Iterates through the string, for each character:

• Gets the ascii value of the character
• If between 65 and 90 (inclusive) add 32, else leave as is
• Print the char corresponding to that value

Code Explanation

: f                   \ start new word definition
  0 do                \ start counted loop from 0 to string-length - 1
    dup i +           \ duplicate the string address and add the loop index
    c@                \ get the ascii char value at that address
    dup 65 91 within  \ check if value is between 65 and 90 (-1 = true, 0 = false)
    32 * -            \ multiply result by 32 and subtract from original number
    emit              \ output value
  loop                \ end loop
;                     \ end word definition

Answer 43

><>, 17 bytes

i::" @["{)${(**+o

Try it online!

Answer 44

J, 39 bytes

((<&91*64&<)(32+#)`(I.@[)`]}])&.(a.i.])

Try it online!

Convert the string to indexes within the J alphabet a., create a mask for those that are uppercase (<&91*64&<), then use amend } to update just those indexes I. that are uppercase with their lowercase counterpart (32+#)

Answer 45

JavaScript(ES6), 92/90 bytes

prompt().split('').map(x=>String.fromCharCode((y=x.charCodeAt(),y>64&y<91)?y+32:y)).join('')

l=a=>a.split('').map(x=>String.fromCharCode((y=x.charCodeAt(),y>64&y<91)?y+32:y)).join('')

Turn the input string into a char array, turn all uppercase letters into lowercase, and turn it back into a string.(Difference between uppercase letter and lowercase letter('a'-'A') is 32, 64 is '@', 91 is '['.)

If using alerts is required, that increases the characters by 7, which means it's 99 bytes.

Answer 46

Powershell - 81 characters

Program:

param($s);[char[]]$s|%{if($_-lt90-and$_-gt64){$n+=[char](+$_+32)}else{$n+=$_}};$n

Example Usage:

.\lower.ps1 -s "TEST!"

Output:

test!

How it works:

It just adds 32 to the decimal value of the ASCII character, which is the lowercase version.
It only does this if it is within 64-90, which is all capital letters.

Answer 47

Delphi XE3 (153 chars)

uses System.SysUtils;var u:string;i:int8;begin readln(u);for i:=1to Length(u)do if CharInSet(u[i],['A'..'Z'])then u[i]:=Chr(Ord(u[i])+32);writeln(u);end.

Not a winner but fun to do :)

with indent

uses
  System.SysUtils;
var
  u:string;
  i:int8;
begin
  readln(u);
  for i:=1to Length(u)do
    if CharInSet(u[i],['A'..'Z'])then
      u[i]:=Chr(Ord(u[i])+32);
    writeln(u);
end.

Answer 48

J 35

echo(+32*64&<*.95&>)&.(a.&i.)1!:1]3

Using the magical under &.. This looks up the ascii code, then adds 32 * the boolean inRange , where inRange is x>64 and x<91. The under operation automatically applies the inverse lookup afterwards, resulting in the wanted lowercase.

In action:

   echo(+32*64&<*.91&>)&.(a.&i.)1!:1]3
Hello World AZ!
hello world az!

Answer 49

Python 3, 78 bytes

t=input()
for c in t:
 x=ord(c)
 if 64<x<91:t=t.replace(c,chr(x+32))
print(t)