Long multiplication: Difference between revisions

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 =={{header|Arturo}}==
+{{trans|ATS}}
-{{Incorrect|Arturo|Task is "Implement long multiplication" not "Multiply two numbers using native operators"}}
-<syntaxhighlight lang="rebol">print 2^64 * 2</syntaxhighlight>
+The program is written to operate on strings containing digits and spaces.
+<syntaxhighlight lang="arturo">
+; The following two functions assume the 7-bit encoding is ASCII.
+char2BCD: function [c] [
+  return (and (to :integer c) 15) % 10
+]
+BCD2char: function [i] [
+  return (to :char (or i 48))
+]
+multiplyBCD: function [u v] [
+  m: size u
+  n: size v
+  w: array.of: (m + n) `0`
+  predm: m - 1
+  predn: n - 1
+  predszw: (size w) - 1
+  ; Long multiplication. See Algorithm 4.3.1M in Volume 2 of Knuth,
+  ; ‘The Art of Computer Programming’. Here b = 10. Only the less
+  ; significant nibble of a character is considered. Thus zero can be
+  ; represented by either `0` or ` `, and other digits by their
+  ; respective ASCII characters.
+  loop 0..predn 'j [
+    vj: char2BCD v\[predn - j]
+    if? vj = 0 [
+      set w (predn - j) `0`
+    ] else [
+      carry: 0
+      loop 0..predm 'i [
+        ui: char2BCD u\[predm - i]
+        wij: char2BCD w\[predszw - (i + j)]
+        t: (ui * vj) + wij + carry
+        [carry digit]: divmod t 10
+        set w (predszw - (i + j)) (BCD2char digit)
+      ]
+      set w (predn - j) (BCD2char carry)
+    ]
+  ]
+  return join w
+]
+twoRaised64: "18446744073709551616"
+twoRaised128: multiplyBCD twoRaised64 twoRaised64
+print twoRaised128
+</syntaxhighlight>
 {{out}}
-<pre>340282366920938463463374607431768211456</pre>
+<pre>0340282366920938463463374607431768211456</pre>
 =={{header|ATS}}==