Just another update

Task/Exponentiation-operator/00META.yaml

@@ -1,2 +1,4 @@
 ---
+category:
+- Arithmetic
 note: Arithmetic operations

Task/Exponentiation-operator/C/exponentiation-operator-2.c

@@ -0,0 +1,13 @@
+#define generic_pow(base, exp)\
+    _Generic((base),\
+            double: dpow,\
+            int: ipow)\
+    (base, exp)
+
+int main()
+{
+    printf("2^6 = %d\n", generic_pow(2,6));
+    printf("2^-6 = %d\n", generic_pow(2,-6));
+    printf("2.71^6 = %lf\n", generic_pow(2.71,6));
+    printf("2.71^-6 = %lf\n", generic_pow(2.71,-6));
+}

Task/Exponentiation-operator/D/exponentiation-operator.d

@@ -1,12 +1,12 @@
 import std.stdio, std.conv;
 
 struct Number(T) {
-    T x; // Base.
+    T x; // base
     alias x this;
     string toString() const { return text(x); }
 
     Number opBinary(string op)(in int exponent)
-    const pure nothrow if (op == "^^") in {
+    const pure nothrow @nogc if (op == "^^") in {
         if (exponent < 0)
             assert (x != 0, "Division by zero");
     } body {
@@ -16,7 +16,7 @@ struct Number(T) {
         T factor;
         if (exponent < 0) {
             zerodir = +1;
-            factor = (cast(T)1) / x;
+            factor = T(1) / x;
         } else {
             zerodir = -1;
             factor = x;

Task/Exponentiation-operator/Perl/exponentiation-operator-2.pl

@@ -0,0 +1,13 @@
+sub ex {
+  my($base,$exp) = @_;
+  die "Exponent '$exp' must be an integer!" if $exp != int($exp);
+  return 1 if $exp == 0;
+  ($base, $exp) = (1/$base, -$exp)  if $exp < 0;
+  my $c = 1;
+  while ($exp > 1) {
+    $c *= $base if $exp % 2;
+    $base *= $base;
+    $exp >>= 1;
+  }
+  $base * $c;
+}

Task/Exponentiation-operator/Prolog/exponentiation-operator-1.pro

@@ -0,0 +1,2 @@
+:- arithmetic_function((^^)/2).
+:- op(200, xfy, user:(^^)).

Task/Exponentiation-operator/Prolog/exponentiation-operator-2.pro

@@ -0,0 +1,24 @@
+%% ^^/3
+%
+%   True if Power is Base ^ Exp.
+
+^^(Base, Exp, Power) :-
+    ( Exp < 0   ->  Power is 1 / (Base ^^ (Exp * -1))            % If exponent is negative, then ...
+
+    ; Exp > 0   ->  length(Powers, Exp),                         % If exponent is positive, then
+                    foldl( exp_folder(Base), Powers, 1, Power )  %    Powers is a list of free variables with length Exp
+                                                                 %    and Power is Powers folded with exp_folder/4
+
+    ; Power = 1                                                  % otherwise Exp must be 0, so
+    ).
+
+%% exp_folder/4
+%
+%       True when Power is the product of Base and Powers.
+%
+%       This predicate is designed to work with foldl and a list of free variables.
+%       It passes the result of each evaluation to the next application through its
+%       fourth argument, instantiating the elements of Powers to each successive Power of the Base.
+
+exp_folder(Base, Power, Powers, Power) :-
+    Power is Base * Powers.

Task/Exponentiation-operator/Prolog/exponentiation-operator-3.pro

@@ -0,0 +1,11 @@
+?- X is 2 ^^ 3.
+X = 8.
+
+?- X is 2 ^^ -3.
+X = 0.125.
+
+?- X is 2.5 ^^ -3.
+X = 0.064.
+
+?- X is 2.5 ^^ 3.
+X = 15.625.

Task/Exponentiation-operator/Prolog/exponentiation-operator-4.pro

@@ -0,0 +1,16 @@
+exp_recursive(Base, NegExp, NegPower) :-
+    NegExp < 0,
+    Exp is NegExp * -1,
+    exp_recursive_(Base, Exp, Base, Power),
+    NegPower is 1 / Power.
+exp_recursive(Base, Exp, Power) :-
+    Exp > 0,
+    exp_recursive_(Base, Exp, Base, Power).
+exp_recursive(_, 0, 1).
+
+exp_recursive_(_,    1,   Power, Power).
+exp_recursive_(Base, Exp, Acc,   Power)   :-
+    Exp > 1,
+    NewAcc is Base * Acc,
+    NewExp is Exp  - 1,
+    exp_recursive_(Base, NewExp, NewAcc, Power).

Task/Exponentiation-operator/Seed7/exponentiation-operator-2.seed7

@@ -1,44 +1,32 @@
 const func float: fltIPow (in var float: base, in var integer: exponent) is func
   result
-    var float: result is 0.0;
+    var float: power is 1.0;
   local
-    var boolean: neg_exp is FALSE;
+    var integer: stop is 0;
   begin
     if base = 0.0 then
       if exponent < 0 then
-        result := Infinity;
-      elsif exponent = 0 then
-        result := 1.0;
-      else
-        result := 0.0;
+        power := Infinity;
+      elsif exponent > 0 then
+        power := 0.0;
       end if;
     else
       if exponent < 0 then
-        exponent := -exponent;
-        neg_exp := TRUE;
+        stop := -1;
       end if;
-      # In the twos complement representation the most
-      # negative number is the only one where both the
-      # number and its negation are negative. When the
-      # exponent is proven to be to the most negative
-      # number fltIPow returns 0.0 .
-      if exponent >= 0 then
+      if odd(exponent) then
+        power := base;
+      end if;
+      exponent >>:= 1;
+      while exponent <> stop do
+        base *:= base;
         if odd(exponent) then
-          result := base;
-        else
-          result := 1.0;
+          power *:= base;
         end if;
         exponent >>:= 1;
-        while exponent <> 0 do
-          base *:= base;
-          if odd(exponent) then
-            result *:= base;
-          end if;
-          exponent >>:= 1;
-        end while;
-        if neg_exp then
-          result := 1.0 / result;
-        end if;
+      end while;
+      if stop = -1 then
+        power := 1.0 / power;
       end if;
     end if;
   end func;