Android Question Solved - String to long integer odd issue

padvou · Nov 10, 2020

Hi!
Consider this string: 637406139915958403 and this: 637406139915958402
using this sub:

B4X:

Sub CI(str As String) As Long
    If IsNumber(str) Then
    Try
        Dim ret As Long
        ret = str
        Return ret
    Catch
        Return 0
    End Try
    Else
        Return 0
    End If
End Sub

returns 637406139915958400 in both strings.
Why??

OliverA · Nov 10, 2020

Almost looks like the values are first converted to a Double and then to ~~an Int~~ a Long

B4X:

    Dim one As String = "637406139915958402"
    Dim two As String = "637406139915958403"
    Dim double1 As Double = one
    Dim double2 As Double = two
    Log($"$18{double1}"$)
    Log($"$18{double2}"$)

Output:

double1: 637,406,139,915,958,400
double2: 637,406,139,915,958,400

OliverA · Nov 10, 2020

Confirmed

B4X:

    Dim one As String = "637406139915958402"
    Dim long1 As Long = one

The resulting Java code fo the long1 assignment is

Java:

_long1 = (long)(Double.parseDouble(_one));

OliverA · Nov 10, 2020

A solution: Use @agraham's BigNumbers library (https://www.b4x.com/android/forum/threads/bignumbers-library.9540/#content):

B4X:

    Dim one As String = "637406139915958402"
    Dim bigN As BigInteger
    bigN.Initialize(one)
    Dim long1 As Long = bigN.LongValue
    Log($"long1: ${long1}"$)

Result:

long1: 637406139915958402

Android Question Solved - String to long integer odd issue

padvou

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OliverA

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Android Question Solved - String to long integer odd issue

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