Another update from ingydotnet^djgoku

Task/Undefined-values/Fortran/undefined-values.f

@@ -0,0 +1 @@
+IsNaN(x)

Task/Undefined-values/Perl-6/undefined-values-4.pl6

@@ -0,0 +1,7 @@
+my Int:D $i = 1; # if $i has to be defined you must provide a default value
+multi sub foo(Int:D $i where * != 0){ (0..100).roll / $i } # we will never divide by 0
+multi sub foo(Int:U $i){ die 'WELP! $i is undefined' } # because undefinedness is deadly
+multi sub foo(Int:_ where * == 0){ die q{I'm sorry, Dave, I'm afraid I can't do that.} }
+
+with $i { say 'defined' } # as "if" is looking for Bool::True, "with" is looking for *.defined
+with 0 { say '0 may not divide but it is defined' }

Task/Undefined-values/Perl-6/undefined-values-5.pl6

@@ -0,0 +1,17 @@
+my $is-defined = 1;
+my $ain't-defined = Any;
+my $doesn't-matter;
+my Any:D $will-be-defined = $ain't-defined // $is-defined // $doesn't-matter;
+
+my @a-mixed-list = Any, 1, Any, 'a';
+$will-be-defined = [//] @a-mixed-list; # [//] will return the first defined value
+
+my @a = Any,Any,1,1;
+my @b = 2,Any,Any,2;
+my @may-contain-any = @a >>//<< @b; # contains: [2, Any, 1, 1]
+
+sub f1(){Failure.new('WELP!')};
+sub f2(){ $_ ~~ Failure }; # orelse will kindly set the topic for us
+my $s = (f1() orelse f2()); # Please note the parentheses, which are needed because orelse is
+                            # much looser then infix:<=> .
+dd $s; # this be Bool::False

Task/Undefined-values/REXX/undefined-values.rexx

@@ -1,23 +1,20 @@
-/*REXX program to test if a variable is defined. */
+/*REXX program test if a (REXX)  variable is  defined  or  not defined.       */
+tlaloc = "rain god of the Aztecs."     /*assign a value to the Aztec rain god.*/
+                                       /*check if the  rain god  is defined.  */
+y= 'tlaloc'
+if symbol(y)=="VAR"  then say y  ' is   defined.'
+                     else say y  "isn't defined."
 
-tlaloc = "rain god of the Aztecs."
+                                       /*check if the  fire god  is defined.  */
+
+y= 'xiuhtecuhtli'                      /*assign a value to the Aztec file god.*/
+if symbol(y)=="VAR"  then say y  ' is   defined.'
+                     else say y  "isn't defined."
 
 
-                    /*check if the rain god is defined.*/
-y='tlaloc'
-if symbol(y)=="VAR" then say y 'is defined.'
-                    else say y "ain't defined."
-
-
-                    /*check if the fire god is defined.*/
-
-y='xiuhtecuhtli'
-if symbol(y)=="VAR" then say y 'is defined.'
-                    else say y "ain't defined."
-
-
-drop tlaloc         /*un-define the  TLALOC  variable. */
-                    /*check if the rain god is defined.*/
-y='tlaloc'
-if symbol(y)=="VAR" then say y 'is defined.'
-                    else say y "ain't defined."
+drop tlaloc                            /*un─define the  TLALOC  REXX variable.*/
+                                       /*check if the  rain god  is defined.  */
+y= 'tlaloc'
+if symbol(y)=="VAR"  then say y  ' is  defined.'
+                     else say y  "isn't defined."
+                                       /*stick a fork in it,  we're all done. */