CODEWITHSUNDEEP
vb.netstring
Taylor K.
Taylor K.

Reputation: 1085

Using InStr to find the first occurence that isn't a certain character

I'm trying to use InStr to find the first character that isn't a "0" (starting from the left-hand side) in strings like this:

000000000001
000000004092
000000000052
000000001006

Can this be done with InStr, or should I use something different?

Upvotes: 2

Views: 1744

Answers (4)

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726609

If you are looking for an index of an item that is not zero (that may also be a non-digit) use this regular expression: [^0]

Dim pos as Integer = Regex.Match(str, "[^0]").Index

Keep in mind, Regex functions require the following library call:

Imports System.Text.RegularExpressions

This will not work well when the string is composed entirely of zeros, so you may want to modify the expression to allow zero to be the last (or the only) character in the string:

`([^0])|(0$)`
          ^--- This meta-character matches an end-of-string marker

Upvotes: 4

Tim Schmelter
Tim Schmelter

Reputation: 460138

If you're using VB.NET you should use .NET methods.

One way is using Enumerable.Where which is a Linq method:

Dim value = "000000000001"
Dim firstNotZero = From c In value Where c <> "0"c
If firstNotZero.Any Then
    Dim first As Char = firstNotZero.First
End If

Edit: If you don't want to use Linq or Regex, you can also use a simple loop:

Dim lines = {"000000000001", "000000004092", "000000000052", "000000001006"}
Dim firstDigits As New List(Of Char)
For Each line In lines
    For Each c In line
        If c <> "0"c Then
            firstDigits.Add(c)
            Exit For
        End If
    Next
Next

This adds all first not 0 characters to a List(Of Char).

Upvotes: 2

SLaks
SLaks

Reputation: 887459

Use regular expressions:

Regex.Match(yourString, "[1-9]")

Upvotes: 1

Oded
Oded

Reputation: 499042

There is no way to "negate" the parameters of InStr.

If you know the input, you can simply search for what should not there (possibly using regex).

It is difficult to give you something less general as an answer without details such as - what is the range of input characters? What rules govern a match? How is this to be used?

Upvotes: 0

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