langs a-z

Task/Factorial/PostScript/factorial-1.ps

@@ -0,0 +1,12 @@
+/fact {
+  dup 0 eq     % check for the argument being 0
+  {
+    pop 1      % if so, the result is 1
+  }
+  {
+    dup
+    1 sub
+    fact       % call recursively with n - 1
+    mul        % multiply the result with n
+  } ifelse
+} def

Task/Factorial/PostScript/factorial-2.ps

@@ -0,0 +1,6 @@
+/fact {
+  1            % initial value for the product
+  1 1          % for's start value and increment
+  4 -1 roll    % bring the argument to the top as for's end value
+  { mul } for
+} def

Task/Factorial/PostScript/factorial-3.ps

@@ -0,0 +1 @@
+/myfact {{dup 0 eq} {pop 1} {dup pred} {mul} linrec}.