Convert decimal number to rational: Difference between revisions

</pre>

=={{header|VBA}}==

<lang VBA>Function Real2Rational(r As Double, bound As Long) As String

If r = 0 Then

Real2Rational = "0/1"

ElseIf r < 0 Then

Result = Real2Rational(-r, bound)

Real2Rational = "-" & Result

Else

best = 1

bestError = 1E+99

For i = 1 To bound + 1

currentError = Abs(i * r - Round(i * r))

If currentError < bestError Then

best = i

bestError = currentError

If bestError < 1 / bound Then GoTo SkipLoop

End If

Next i

SkipLoop:

Real2Rational = Round(best * r) & "/" & best

End If

End Function

Sub TestReal2Rational()

Debug.Print "0.75" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(0.75, CLng(Order));

Next i

Debug.Print

Debug.Print "0.518518" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(0.518518, CLng(Order));

Next i

Debug.Print

Debug.Print "0.9054054" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(0.9054054, CLng(Order));

Next i

Debug.Print

Debug.Print "0.142857143" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(0.142857143, CLng(Order));

Next i

Debug.Print

Debug.Print "3.141592654" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(3.141592654, CLng(Order));

Next i

Debug.Print

Debug.Print "2.718281828" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(2.718281828, CLng(Order));

Next i

Debug.Print

Debug.Print "-0.423310825" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(-0.423310825, CLng(Order));

Next i

Debug.Print

Debug.Print "31.415926536" & ":";

For i = 0 To 5

Order = CDbl(10) ^ CDbl(i)

Debug.Print " " & Real2Rational(31.415926536, CLng(Order));

Next i

End Sub

</lang>

{{out}}

<pre>

0.75: 1/1 3/4 3/4 3/4 3/4 3/4

0.518518: 1/1 1/2 14/27 14/27 14/27 37031/71417

0.9054054: 1/1 1/1 67/74 67/74 67/74 67/74

0.142857143: 0/1 1/7 1/7 1/7 1/7 1/7

3.141592654: 3/1 22/7 22/7 355/113 355/113 104348/33215

2.718281828: 3/1 19/7 193/71 1457/536 23225/8544 173459/63812

-0.423310825: -0/1 -3/7 -11/26 -69/163 -1253/2960 -10093/23843

31.415926536: 31/1 157/5 377/12 3550/113 208696/6643 1563445/49766