################################################################
 #
 # Lambda Calculus demonstration in Perl
 # 4 April 1999 
 # M-J. Dominus (mjd-perl-lc@plover.com)
 # http://www.plover.com/~mjd/perl/lambda/
 #
 ############
 #
 # Truth and truth testing
 # IF = %btf.btf
 $IF = sub { my $b = shift;
 sub { my $t = shift;
 sub { my $f = shift;
 ($b)->($t)->($f);
 }
 }
 }
 ;
 
 # TRUE = %xy.x
 $TRUE = sub { my $x = shift;
 sub { my $y = shift;
 $x;
 }
 }
 ;
 
 # FALSE = %xy.y
 $FALSE = sub { my $x = shift;
 sub { my $y = shift;
 $y;
 }
 }
 ;
 ############
 #
 # Pairs (conses)
 
 # PAIR = %xyb.bxy
 $PAIR = sub { my $x = shift;
 sub { my $y = shift;
 sub { my $b = shift;
 ($b)->($x)->($y);
 }
 }
 }
 ;
 
 # FIRST = %p.(p TRUE)
 $FIRST = sub { my $p = shift;
 ($p)->($TRUE);
 }
 ;
 
 # SECOND = %p.(p FALSE)
 $SECOND = sub { my $p = shift;
 ($p)->($FALSE);
 }
 ;
 
 
 ############
 #
 # Church Numerals
 #
	# 0 = %f.%x.x
	$ZERO = sub { my $f = shift;
		 sub { my $x = shift;
			 $x
			 }
		 }
	;
	# SUCC = %n.%f.%x.f (n f x)
	$SUCC = sub { my $n = shift;
		 sub { my $f = shift;
			 sub { my $x = shift;
				 $f->($n->($f)->($x));
				}
			 }
		 }
	;
	# ONE = SUCC 0
	$ONE = $SUCC->($ZERO);
	# ADD = %mn.%f.%x.(m f) (n f x)
	$ADD = sub { my $m = shift;
		 sub { my $n = shift;
			 sub { my $f = shift;
				 sub { my $x = shift;
				 ($m->($f))->($n->($f)->($x));
				 }
			 }
			 }
		 }
	;
	# IS_ZERO = %n.(n (%k.FALSE) TRUE)
	$IS_ZERO = sub { my $n = shift;
			 $n->(sub { my $k = shift; $FALSE })->($TRUE);
		 }
	;
 ############
 #
 # We use this utility function only for checking to see if the
 # addition was done correctly
 # 
	sub convert_to_perl_number {
	 my $n = shift;
	 $n->(sub {my $n = shift; $n+1})->(0);
	}
	$mystery_result = $ADD->($ONE)->($ONE);
	print "1+1 = ", convert_to_perl_number($mystery_result), "\n";
</div><div class="naked_ctrl">
<form action="/index.cgi/larger-text" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://perl.plover.com/lambda/jfp/lambda-church.pl">(-&gt;オリジナル)</a>
/ <label>アドレス: <input type="text" name="naked_post_url" value="https://perl.plover.com/lambda/jfp/lambda-church.pl" size="22" /></label> <label>モード: <select name="naked_post_mode">
<option value="default">デフォルト</option>
<option value="speech">音声ブラウザ</option>
<option value="ruby">ルビ付き</option>
<option value="contrast">配色反転</option>
<option value="larger-text" selected="selected">文字拡大</option>
<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
</p>
</form>
</div>