Long multiplication: Difference between revisions
added FreeBASIC
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end program Test</lang>
=={{header|FreeBASIC}}==
<lang freebasic>' version 08-01-2017
' compile with: fbc -s console
Const As UInteger base_ = 1000000000 ' base 1,000,000,000
Function multiply(a1 As String, b1 As String) As String
Dim As String a = a1, b = b1
Trim(a) : Trim(b) ' remove spaces
If Len(a) = 0 Or Len(b) = 0 Then Return "0"
If Len(a) + Len(b) > 10000 Then
Print "number(s) are to big"
Sleep 5000,1
Return ""
End If
If Len(a) < Len(b) Then
Swap a, b
End If
Dim As ULongInt product
Dim As UInteger carry, i, m, shift
Dim As UInteger la = Len(a), lb = Len(b)
Dim As UInteger la9 = la \ 9 + IIf((la Mod 9) = 0, 0, 1)
Dim As UInteger lb9 = lb \ 9 + IIf((lb Mod 9) = 0, 0, 1)
Dim As UInteger arr_a(la9), answer((la9 + lb9) + 2)
Dim As Integer last = la9
' make length a, b a multipy of 9
a = Right((String(9, "0") + a), la9 * 9)
b = Right((String(9, "0") + b), lb9 * 9)
For i = 1 To la9
arr_a(la9 - i +1) = Val(Mid(a, i * 9 -8, 9))
Next
Do
carry = 0
m = Val(Mid(b, lb9 * 9 -8, 9))
For i = 1 To la9
product = CULngInt(arr_a(i)) * m + answer(i + shift) + carry
carry = product \ base_
answer(i + shift) = product - carry * base_
Next
If carry <> 0 Then
last = la9 + shift +1
answer(last) = carry
End If
lb9 = lb9 -1
shift = shift +1
Loop Until lb9 = 0
Dim As String tmp = Str(answer(last))
last = last -1
While last > 0
tmp = tmp + Right(String(9,"0") + Str(answer(last)), 9)
last = last -1
Wend
Return tmp
End Function
' ------=< MAIN >=------
Dim As String a = "2", b = "2", answer
Dim As UInteger i = 1, j
For j = 1 To 7
answer = multiply(a, b)
a = answer
b = answer
i = i + i
Print using "2 ^ ### = "; i;
Print answer
Next
Print
Print "-------------------------------------------------"
Print
a = "2" : b = "1" : answer = ""
For j = 1 To 128
answer = multiply(a, b)
b = answer
Next
Print "2 ^ 128 = "; answer
' empty keyboard buffer
While InKey <> "" : Wend
Print : Print "hit any key to end program"
Sleep
End</lang>
{{out}}
<pre>2 ^ 2 = 4
2 ^ 4 = 16
2 ^ 8 = 256
2 ^ 16 = 65536
2 ^ 32 = 4294967296
2 ^ 64 = 18446744073709551616
2 ^ 128 = 340282366920938463463374607431768211456
-------------------------------------------------
2 ^ 128 = 340282366920938463463374607431768211456</pre>
=={{header|Go}}==
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