Case-sensitivity of identifiers

Three dogs (Are there three dogs or one dog?) is a code snipped used to illustrate the lettercase sensitivity of the programming language. For a case sensitive language, the identifiers dog, Dog and DOG are all different and we should get the output:

The three dogs are named Benjamin, Samba and Bernie.

For a language that is lettercase insensitive, we get the following output:

There is just one dog named Bernie.

AWK

<lang awk>BEGIN { dog = "Benjamin" Dog = "Samba" DOG = "Bernie" printf "The three dogs are named %s, %s and %s.\n", dog, Dog, DOG }</lang>

The three dogs are named Benjamin, Samba and Bernie.

bc

The only variables are 'a' through 'z'. They can only hold numbers, not strings. Some implementations allow longer names like 'dog', but only with lowercase letters. A name like 'Dog' or 'DOG' is a syntax error.

<lang bc>obase = 16 ibase = 16

/*

* Store the hexadecimal number 'BE27A312'
* in the variable 'd'.
*/

d = BE27A312 "There is just one dog named "; d quit</lang>

There is just one dog named BE27A312

Common Lisp

<lang lisp>CL-USER> (let* ((dog "Benjamin") (Dog "Samba") (DOG "Bernie")) (format nil "There is just one dog named ~a." dog))

in: LAMBDA NIL
(LET* ((DOG "Benjamin") (DOG "Samba") (DOG "Bernie"))
(FORMAT NIL "There is just one dog named ~a." DOG))

caught STYLE-WARNING
The variable DOG is defined but never used.

caught STYLE-WARNING
The variable DOG is defined but never used.

compilation unit finished
caught 2 STYLE-WARNING conditions

"There is just one dog named Bernie."</lang>

dc

A register name has only one character, so this example uses 'd' and 'D'.

<lang dc>[Benjamin]sd [Samba]sD [The two dogs are named ]P ldP [ and ]P lDP [. ]P</lang>

The two dogs are named Benjamin and Samba.

Euphoria

Works with: Euphoria 4.0.0

<lang Euphoria>-- These variables are all different sequence dog = "Benjamin" sequence Dog = "Samba" sequence DOG = "Bernie" printf( 1, "The three dogs are named %s, %s and %s\n", {dog, Dog, DOG} )</lang>

Icon and Unicon

The program below demonstrates the three dog task. All variants of Icon/Unicon have case sensitive variable names. But if one wasn't this would find it. <lang Icon>procedure main()

  dog := "Benjamin"
  Dog := "Samba"
  DOG := "Bernie"

  if dog == DOG then 
     write("There is just one dog named ", dog,".") 
  else 
     write("The three dogs are named ", dog, ", ", Dog, " and ", DOG, ".")

end</lang>

J

<lang j> NB. These variables are all different

  dog=: 'Benjamin'
  Dog=: 'Samba'
  DOG=: 'Bernie'
  'The three dogs are named ',dog,', ',Dog,', and ',DOG

The three dogs are named Benjamin, Samba, and Bernie </lang>

Java

<lang java>String dog = "Benjamin"; String Dog = "Samba"; //in general, identifiers that start with capital letters are class names String DOG = "Bernie"; //in general, identifiers in all caps are constants //the conventions listed in comments here are not enforced by the language System.out.println("There are three dogs named " + dog + ", " + Dog + ", and " + DOG + "'");</lang>

Perl

<lang perl># These variables are all different $dog='Benjamin'; $Dog='Samba'; $DOG='Bernie'; print "The three dogs are named $dog, $Dog, and $DOG \n"</lang>

PicoLisp

<lang PicoLisp>(let (dog "Benjamin" Dog "Samba" DOG "Bernie")

  (prinl "The three dogs are named " dog ", " Dog " and " DOG) )</lang>

Output:

The three dogs are named Benjamin, Samba and Bernie

Prolog

In Prolog, the initial of a variable must be a uppercase letter. So the task can't be completed but we can write this code : <lang Prolog>three_dogs :- DoG = 'Benjamin', Dog = 'Samba', DOG = 'Bernie', format('The three dogs are named ~w, ~w and ~w.~n', [DoG, Dog, DOG]). </lang> The output is :

?- three_dogs.
The three dogs are named Benjamin, Samba and Bernie.
true.

PureBasic

<lang PureBasic>dog$="Benjamin" Dog$="Samba" DOG$="Bernie" Debug "There is just one dog named "+dog$</lang>

Python

Python names are case sensitive: <lang python>>>> dog = 'Benjamin'; Dog = 'Samba'; DOG = 'Bernie' >>> print ('The three dogs are named ',dog,', ',Dog,', and ',DOG) The three dogs are named Benjamin , Samba , and Bernie >>> </lang>

Ruby

Ruby gives a special meaning to the first letter of a name. A lowercase letter starts a local variable. An uppercase letter starts a constant. So dog is a local variable, but Dog and DOG are constants. To adapt this task to Ruby, I added dOg and doG so that I have more than one local variable.

<lang ruby>module FiveDogs

 dog = "Benjamin"
 dOg = "Dogley"
 doG = "Fido"
 Dog = "Samba"   # this constant is FiveDogs::Dog
 DOG = "Bernie"  # this constant is FiveDogs::DOG

 names = [dog, dOg, doG, Dog, DOG]
 names.uniq!
 puts "There are %d dogs named %s." % [names.length, names.join(", ")]
 puts
 puts "The local variables are %s." % local_variables.join(", ")
 puts "The constants are %s." % constants.join(", ")

end</lang>

Output:

There are 5 dogs named Benjamin, Dogley, Fido, Samba, Bernie.

The local variables are dog, dOg, doG, names.
The constants are Dog, DOG.

Tcl

Tcl variable names are case sensitive: <lang tcl>set dog "Benjamin" set Dog "Samba" set DOG "Bernie" puts "The three dogs are named $dog, $Dog and $DOG"</lang> Which prints...

The three dogs are named Benjamin, Samba and Bernie

UNIX Shell

<lang bash>dog="Benjamin" Dog="Samba" DOG="Bernie" echo "The three dogs are named $dog, $Dog and $DOG."</lang>

The three dogs are named Benjamin, Samba and Bernie.