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A narcissist (or Narcissus program) is the decision-problem version of a quine.

A quine, when run, takes no input, but produces a copy of its own source code at its output. In contrast, a narcissist reads a string of symbols from its input, and produces no output except a "1" or "accept" if that string matches its own source code, or a "0" or "reject" if it does not.

For concreteness, in this task we shall assume that symbol = character.

The narcissist should be able to cope with any finite input, whatever its length.

Any form of output is allowed, as long as the program always halts, and "accept", "reject" and "not yet finished" are distinguishable.

Ada

Works with: Ada 2005

Took code from Quine, has to be in one line (could be done pretty printed, too, but not as simple).

<lang Ada>with Ada.Text_IO;procedure Self is Q:Character:='"';A:String:="with Ada.Text_IO;procedure Self is Q:Character:=;A:String:=;B:String:=A(1..49)&Q&A(50..61)&Q&A&Q&A(62..A'Last);C:String:=Ada.Text_IO.Get_Line;begin Ada.Text_IO.Put_Line(Boolean'Image(B=C));end Self;";B:String:=A(1..49)&Q&A(50..61)&Q&A&Q&A(62..A'Last);C:String:=Ada.Text_IO.Get_Line;begin Ada.Text_IO.Put_Line(Boolean'Image(B=C));end Self;</lang>

ALGOL 68

Works with: ALGOL 68 version Revision 1 - no extensions to language used

Works with: ALGOL 68G version Any - tested with release 1.18.0-9h.tiny

<lang algol68>STRINGs="STRINGs="";print(readstring=2*s[:9]+2*s[9:])";print(readstring=2*s[:9]+2*s[9:])</lang> Output: T or F depending on input.

AutoHotkey

Works with: AutoHotkey 1.1

<lang AutoHotkey>Narcissist(Input) { FileRead, Source, % A_ScriptFullPath return Input == Source ? "accept" : "reject" }</lang> Example Use: <lang AutoHotkey>MsgBox, % Narcissist(FileOpen(A_ScriptFullPath, "r").Read()) "`n" . Narcissist("This isn't the text you're looking for.")</lang>

Output:

accept
reject

BBC BASIC

Works with: BBC BASIC for Windows

Prints '1' on success and '0' on failure. <lang bbcbasic>INPUT a$:PRINT -(a$=$(PAGE+34)+$(PAGE+33)):REM INPUT a$:PRINT -(a$=$(PAGE+34)+$(PAGE+33)):REM</lang>

Befunge

Reads from stdin up to the first carriage return, line feed, or EOF. However, the latter is not guaranteed to work on all Befunge implementations - in particular not on Befunge-98 - so a line break is recommended.

Outputs 1 if the given line of input matches the source code, and 0 if it doesn't.

C

Based upon the quine. Reads until EOF or newline from stdin, and writes "1" or "0" to stdout. <lang c>extern void*stdin;main(){ char*p = "extern void*stdin;main(){ char*p = %c%s%c,a[300],b[300];sprintf(a,p,34,p,34);fgets(b,300,stdin);putchar(48+!strcmp(a,b)); }",a[300],b[300];sprintf(a,p,34,p,34);fgets(b,300,stdin);putchar(48+!strcmp(a,b)); }</lang>

C#

<lang csharp> using System; using System.IO; using System.Text; using System.Text.RegularExpressions; namespace Narcisisst { class Program { public static void Main(string[] args) { const string path = @"E:\Narcisisst"; string[] thisFile = Directory.GetFiles(path , "Program.cs"); StringBuilder sb = new StringBuilder();

foreach (string readLine in File.ReadLines(thisFile[0])) { sb.Append(readLine); sb.Append("\n"); }

Console.WriteLine(sb); string input =String.Empty; input = Console.ReadLine(); Console.WriteLine((Regex.IsMatch(sb.ToString(),input))?"accept":"reject"); Console.ReadKey(); } } } </lang>

Common Lisp

Only checks the first line of stdin: <lang lisp>#1=(PRINT (EQUAL (WRITE-TO-STRING '#1# :CIRCLE 1) (READ-LINE *STANDARD-INPUT*)))</lang>

D

<lang D>import std.file; import std.stdio; import std.string; void main() { auto source = readText("narcissist.d").chomp; auto input = readln().chomp(); if (source == input) writeln("accept"); else writeln("reject"); }</lang>

Déjà Vu

<lang dejavu>!. = !prompt "Enter my code: " concat( swap !decode!utf-8 !encode!quoted dup swap ) "!. = !prompt \qEnter my code: \q concat( swap !decode!utf-8 !encode!quoted dup swap ) "</lang>

Forth

<lang forth>: narcissist [ source ] sliteral compare 0= ;</lang>

Go

This version reads until EOF and expects a newline at the end of the input. If this is being checked from a file, make sure that the file has exactly one newline at the end of it.

<lang go>package main; import "os"; import "fmt"; import "bytes"; import "io/ioutil"; func main() {ios := "os"; ifmt := "fmt"; ibytes := "bytes"; iioutil := "io/ioutil"; zero := "Reject"; one := "Accept"; x := "package main; import %q; import %q; import %q; import %q; func main() {ios := %q; ifmt := %q; ibytes := %q; iioutil := %q; zero := %q; one := %q; x := %q; s := fmt.Sprintf(x, ios, ifmt, ibytes, iioutil, ios, ifmt, ibytes, iioutil, zero, one, x); in, _ := ioutil.ReadAll(os.Stdin); if bytes.Equal(in, []byte(s)) {fmt.Println(one);} else {fmt.Println(zero);};}\n"; s := fmt.Sprintf(x, ios, ifmt, ibytes, iioutil, ios, ifmt, ibytes, iioutil, zero, one, x); in, _ := ioutil.ReadAll(os.Stdin); if bytes.Equal(in, []byte(s)) {fmt.Println(one);} else {fmt.Println(zero);};}</lang> A version respecting the 80 character line limit: <lang go>package main

import (

   "bytes"
   "fmt"
   "io/ioutil"
   "os"

)

func main() {

   s := fmt.Sprintf("%s%c%s%c\n", x, 0x60, x, 0x60)
   in, _ := ioutil.ReadAll(os.Stdin)
   if bytes.Equal(in, []byte(s)) {
       fmt.Println("Accept")
   } else {
       fmt.Println("Reject")
   }

}

var x = `package main

import (

   "bytes"
   "fmt"
   "io/ioutil"
   "os"

)

func main() {

   s := fmt.Sprintf("%s%c%s%c\n", x, 0x60, x, 0x60)
   in, _ := ioutil.ReadAll(os.Stdin)
   if bytes.Equal(in, []byte(s)) {
       fmt.Println("Accept")
   } else {
       fmt.Println("Reject")
   }

}

var x = `</lang>

Haskell

Huginn

<lang huginn>#! /bin/sh exec huginn --no-argv -E "${0}"

! huginn

main() { c = "#! /bin/sh{1}~" "exec huginn --no-argv -E {3}$Template:0{3}{1}#! huginn{1}{1}~" "main() {{{1}{2}c = {3}{0}{3};{1}~" "{2}s = {3}{3};{1}~" "{2}while ( ( line = input() ) != none ) {{{1}~" "{2}{2}s += line;{1}~" "{2}}}{1}~" "{2}self = copy( c ).replace( {3}{5}{3}, {3}{3} )~" ".format({1}{2}{2}c.replace( {3}{5}{3}, ~" "{3}{5}{4}{3}{4}n{4}t{4}t{4}{3}{3} ), ~" "{3}{4}n{3}, {3}{4}t{3}, {3}{4}{3}{3}, {3}{4}{4}{3}, ~" "{3}{5}{3}{1}{2});{1}~" "{2}print( s == self ? {3}1{4}n{3} : {3}0{4}n{3} );{1}}}{1}{1}"; s = ""; while ( ( line = input() ) != none ) { s += line; } self = copy( c ).replace( "~", "" ).format( c.replace( "~", "~\"\n\t\t\"" ), "\n", "\t", "\"", "\\", "~" ); print( s == self ? "1\n" : "0\n" ); } </lang>

Icon and Unicon

Translation of: Go

Since we can't put a link statement and program on a single line, we implement a simplified inline sprintf so we don't have to deal with all the double quotes or substrings and offsets. If we'd needed to write multiple procedures on a line it can be done Semi-colons in the language intro <lang Icon>procedure main();yes:="Accept";no:="Reject";pat:="procedure main();yes:=$;no:=$;pat:=$;a:=[yes,no,pat];narc:=char(0)[0:0];pat?{while narc||:=tab(find(char(36))) do{narc||:=image(get(a));move(1)};narc||:=tab(0)};write(if read()==narc then yes else no);end";a:=[yes,no,pat];narc:=char(0)[0:0];pat?{while narc||:=tab(find(char(36))) do{narc||:=image(get(a));move(1)};narc||:=tab(0)};write(if read()==narc then yes else no);end</lang>

Example:

./narcissist.exe < narcissist.icn
Accept

Actually, this version recognizes all files where the first line is the Narcissist.

J

<lang j>#!/j602/bin/jconsole main=:3 : 0

 self=: '#!/j602/bin/jconsole',LF,'main=:',(5!:5<'main'),LF,'main,LF
 echo  self -: stdin

) main</lang>

Example use:

<lang>$ ./narcissist.ijs <narcissist.ijs 1

  </lang>

Note that this assumes a suitable os command line.

Alternative solution: <lang j> narcissist=.(-:,~,2#{:)&'(-:,~,2#{:)&</lang>

Example use: <lang j> (-:,~,2#{:)&'(-:,~,2#{:)& '(-:,~,2#{:)' 0

  (-:,~,2#{:)&'(-:,~,2#{:)& '(-:,~,2#{:)&(-:,~,2#{:)&''

1</lang>

Java

<lang java>import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader;

public class Narcissist {

   private static final String SOURCE = "import java.io.BufferedReader;%nimport java.io.IOException;%nimport java.io.InputStreamReader;%n%npublic class Narcissist {%n    private static final String SOURCE = %c%s%c;%n    private static final char QUOTE = 0x22;%n%n    public static void main(String[] args) throws IOException {%n        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));%n        StringBuilder sb = new StringBuilder();%n%n        while (true) {%n            String line = br.readLine();%n            if (null == line) break;%n            sb.append(line).append(System.lineSeparator());%n        }%n%n        String program = String.format(SOURCE, QUOTE, SOURCE, QUOTE, QUOTE, QUOTE, QUOTE, QUOTE);%n        if (program.equals(sb.toString())) {%n            System.out.println(%caccept%c);%n        } else {%n            System.out.println(%creject%c);%n        }%n    }%n}%n";
   private static final char QUOTE = 0x22;

   public static void main(String[] args) throws IOException {
       BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
       StringBuilder sb = new StringBuilder();

       while (true) {
           String line = br.readLine();
           if (null == line) break;
           sb.append(line).append(System.lineSeparator());
       }

       String program = String.format(SOURCE, QUOTE, SOURCE, QUOTE, QUOTE, QUOTE, QUOTE, QUOTE);
       if (program.equals(sb.toString())) {
           System.out.println("accept");
       } else {
           System.out.println("reject");
       }
   }

} </lang>

JavaScript

Works with: SpiderMonkey version 1.7.0

Based upon one of the quines. Outputs 'true' if source is equal to inputted line (newline terminated), 'false' otherwise. <lang javascript>var code='var q=String.fromCharCode(39);print("var code=" + q + code + q + "; eval(code)" == readline())'; eval(code)</lang>

Works with: JScript

<lang javascript>var oFSO = new ActiveXObject("Scripting.FileSystemObject"); function readfile(fname) { var h = oFSO.OpenTextFile(fname, 1, false); var result = h.ReadAll(); h.Close(); return result; }

if (0 === WScript.Arguments.UnNamed.Count) { WScript.Echo(WScript.ScriptName,"filename"); WScript.Quit(); }

// first read self var self = readfile(WScript.ScriptFullName); // read whatever file is given on commmand line var whatever = readfile(WScript.Arguments.UnNamed(0));

// compare and contrast WScript.Echo(self === whatever ? "Accept" : "Reject"); </lang>

Julia

<lang julia> input = Base.readstring(ARGS[1]) mysource = Base.readstring(Base.source_path()) println(input == mysource ? "1" : "0") </lang>

Kotlin

<lang scala>// version 1.1.0 (run on Windows 10)

fun main(args: Array<String>) {

   val text = java.io.File("narcissist.kt").readText()
   println("Enter the number of lines to be input followed by those lines:\n")
   val n = readLine()!!.toInt()
   val lines = Array<String>(n) { readLine()!! }
   if (lines.joinToString("\r\n") == text) println("\naccept") else println("\nreject")

}</lang> First run (pasting in program text):

Output:

Enter the number of lines to be input followed by those lines:

9
// version 1.1.0 (run on Windows 10)

fun main(args: Array<String>) {
    val text = java.io.File("narcissist.kt").readText()
    println("Enter the number of lines to be input followed by those lines:\n")
    val n = readLine()!!.toInt()
    val lines = Array<String>(n) { readLine()!! }
    if (lines.joinToString("\r\n") == text) println("\naccept") else println("\nreject")
}

accept

Second run (entering any old rubbish):

Output:

Enter the number of lines to be input followed by those lines:

1
the quick brown fox

reject

Liberty BASIC

NOTE: You have to manually type in ALL of the code since the Input statement will not successfully input data from a paste event even though it will show up in the MainWin.

s$ = "s$ = Input a$ : Print (a$ = Left$(s$, 5) + chr$(34) + s$ + chr$(34) + Mid$(s$, 14, 3) + Mid$(s$, 6, 100)) + Mid$(s$, 23, 3)" : Input a$ : Print (a$ = Left$(s$, 5) + chr$(34) + s$ + chr$(34) + Mid$(s$, 14, 3) + Mid$(s$, 6, 100))
</lang>

Mathematica

Input:

<lang Mathematica>prog = "prog = ``;\nPrint[InputString[] == \n ToString[StringForm[prog, ToString[prog, InputForm]]]];"; Print[InputString[] ==

  ToString[StringForm[prog, ToString[prog, InputForm]]]];</lang>

Output:

True

PARI/GP

<lang parigp>narcissist()=input()==narcissist</lang>

Run narcissist():

Hello
0

narcissist() = {input() == narcissist;}
1

Perl

<lang perl># this is file narc.pl local $/; print do { open 0; <0> } eq <> ? "accept" : "reject";</lang> Run: <lang>perl narc.pl < narc.pl</lang>

Perl 6

For the narcissist to work you must be very careful with whitespace. The following version works if it is given to standard input as exactly one line terminated by a newline character.

Note how the code takes advantage of Perl 6's ability to nest quoting delimiters.

<lang perl6>EVAL my $self = q{say slurp() eq q[EVAL my $self = q{]~$self~q[}]~10.chr ?? q{Beautiful!} !! q{Not my type.}}</lang>

Output:

$ narcissist='EVAL my $self = q{say slurp() eq q[EVAL my $self = q{]~$self~q[}]~10.chr ?? q{Beautiful!} !! q{Not my type.}}'
$ perl6 -e "$narcissist" <<<"$narcissist"
Beautiful!
$ perl6 -e "$narcissist" <<<"$narcissist # a comment ruining it all" 
Not my type.

Phix

<lang Phix>puts(1,{"\n\ntrue\n\n","\n\nfalse\n\n"}[1+(gets(open(command_line()[2],"r"))!=gets(0))])</lang>

PicoLisp

<lang PicoLisp>(de narcissist (Str)

  (= Str (str narcissist)) )</lang>

Output:

: (narcissist "(Str) (= Str (str narcissist))")
-> T

PowerShell

Works with: PowerShell version 2

<lang PowerShell> function Narcissist { Param ( [string]$String ) If ( $String -eq $MyInvocation.MyCommand.Definition ) { 'Accept' } Else { 'Reject' } } </lang> <lang PowerShell> Narcissist 'Banana'

Narcissist @'

Param ( [string]$String ) If ( $String -eq $MyInvocation.MyCommand.Definition ) { 'Accept' } Else { 'Reject' }

'@ </lang>

Output:

Reject
Accept

Python

Works with: Python version 2

<lang Python> import sys with open(sys.argv[0]) as quine:

   code = raw_input("Enter source code: ")
   if code == quine.read():
       print("Accept")
   else:
       print("Reject")

</lang>

Works with: Python version 3

<lang Python> _='_=%r;print (_%%_==input())';print (_%_==input()) </lang>

Racket

This shows a REPL interaction, where the second expression is what is typed when the code stops to read some input.

<lang Racket> -> ((lambda (x) (equal? (read) (list x (list 'quote x))))

  '(lambda (x) (equal? (read) (list x (list 'quote x)))))

((lambda (x) (equal? (read) (list x (list 'quote x))))

'(lambda (x) (equal? (read) (list x (list 'quote x)))))

t

</lang>

REXX

version 1

(returns 1 or 0) <lang rexx>/*REXX*/ say arg(1)=sourceline(1)</lang>

version 2

(returns accept or reject) <lang rexx>/*REXX*/ say word('reject accept',1+(arg(1)=sourceline(1)))</lang>

Ruby

Translation of the C version. <lang ruby>s = "s = %s%s%s; puts(gets.chomp == (s %% [34.chr, s, 34.chr]) ? 'accept' : 'reject')"; puts(gets.chomp == (s % [34.chr, s, 34.chr]) ? 'accept' : 'reject')</lang> Output:

$ ruby narcissist.rb < narcissist.rb
accept

Scala

<lang scala>import scala.io.StdIn

object Narcissist extends App {

 val text = scala.io.Source.fromFile("Narcissist.scala", "UTF-8").toStream
 println("Enter the number of lines to be input followed by those lines:\n")
 val n = StdIn.readInt()
 val lines = Stream {
   StdIn.readLine()
 }
 if (lines.mkString("\r\n") == text) println("\naccept") else println("\nreject")

}</lang>

Sidef

<lang ruby>say (File.new(__FILE__).open_r.slurp == ARGF.slurp);</lang>

Swift

<lang swift>#! /usr/bin/swift import Foundation

let script = CommandLine.arguments[0] print(script) let mytext = try? String.init(contentsOfFile: script, encoding: .utf8)

var enteredtext = readLine() if mytext == enteredtext {

   print("Accept")

} else {

   print("Reject")

}</lang>

Tcl

With the use of explicit reflexive introspection: <lang tcl>apply {{} {puts [expr {[gets stdin] eq [info level 0]}]}}</lang> Without such commands, using pure generation of strings and lists: <lang tcl>apply {s {puts [expr {[gets stdin]eq[list {*}$s $s]}]}} {apply {s {puts [expr {[gets stdin]eq[list {*}$s $s]}]}}}</lang>

TXR

<lang txr>@(bind my64 "QChuZXh0IDphcmdzKUBmaWxlbmFtZUAobmV4dCBmaWxlbmFtZSlAZmlyc3RsaW5lQChmcmVlZm9ybSAiIilAcmVzdEAoYmluZCBpbjY0IEAoYmFzZTY0LWVuY29kZSByZXN0KSlAKGNhc2VzKUAgIChiaW5kIGZpcnN0bGluZSBgXEAoYmluZCBteTY0ICJAbXk2NCIpYClAICAoYmluZCBpbjY0IG15NjQpQCAgKGJpbmQgcmVzdWx0ICIxIilAKG9yKUAgIChiaW5kIHJlc3VsdCAiMCIpQChlbmQpQChvdXRwdXQpQHJlc3VsdEAoZW5kKQ==") @(next :args) @filename @(next filename) @firstline @(freeform "") @rest @(bind in64 @(base64-encode rest)) @(cases) @ (bind firstline `\@(bind my64 "@my64")`) @ (bind in64 my64) @ (bind result "1") @(or) @ (bind result "0") @(end) @(output) @result @(end) </lang>

Output:

$ txr narcissist.txr narcissist.txr
1

VBA

Based on the quine <lang vb>Public Sub narcissist()

   quote = Chr(34)
   comma = Chr(44)
   cont = Chr(32) & Chr(95)
   rparen = Chr(41)
   n = Array( _

"Public Sub narcissist()", _ " quote = Chr(34)", _ " comma = Chr(44)", _ " cont = Chr(32) & Chr(95)", _ " rparen = Chr(41)", _ " n = Array( _", _ "How many lines?", _ "Line ", _ " x = InputBox(n(5))", _ " flag = True", _ " For i = 0 To 5", _ " If InputBox(n(6) & i) <> n(i) Then flag = False", _ " Next i", _ " For i = 0 To 20", _ " If InputBox(n(6) & i + 6) <> quote & n(i) & quote & comma & cont Then flag = False", _ " Next i", _ " If InputBox(n(6) & 27) <> quote & n(21) & quote & rparen Then flag = False", _ " For i = 7 To 21", _ " If InputBox(n(6) & i + 21) <> n(i) Then flag = False", _ " Next i", _ " Debug.Print IIf(flag, 1, 0)", _ "End Sub")

   x = InputBox(n(5))
   flag = True
   For i = 0 To 5
       If InputBox(n(6) & i) <> n(i) Then flag = False
   Next i
   For i = 0 To 20
       If InputBox(n(6) & i + 6) <> quote & n(i) & quote & comma & cont Then flag = False
   Next i
   If InputBox(n(6) & 27) <> quote & n(21) & quote & rparen Then flag = False
   For i = 7 To 21
       If InputBox(n(6) & i + 21) <> n(i) Then flag = False
   Next i
   Debug.Print IIf(flag, 1, 0)

End Sub</lang>

UNIX Shell

<lang bash>cmp "$0" >/dev/null && echo accept || echo reject</lang>

zkl

<lang zkl>stdin:=File.stdin.read(); thisFileSrc:=File(System.argv[1]).read(); println((stdin==thisFileSrc) and "input matches "+System.argv[1] or "No match");</lang> Since zkl is [usually] compile-when-run, we just compare the contents of source file to stdin.

Output:

$ zkl narcissist.zkl <narcissist.zkl 
input matches narcissist.zkl
$ zkl narcissist.zkl <narcissist3.zkl 
No match

@@ Line 435: / Line 435: @@
 ===version 1===
 (returns &nbsp; '''1''' &nbsp; or &nbsp; '''0''')
-<lang rexx>/*REXX*/    say arg(1)=sourceline(1)</lang>
+<lang rexx>/*REXX*/ say arg(1)=sourceline(1)</lang>
 ===version 2===