I wrote this function to format expressions to where there is a space after each character with the exception of unary operators and the last character:
It works great, but can I improve it?
Code:
Private Function FormatExpression(ByVal expression As String) As String
'Add a space after any '(' and a space before any ')'
expression = expression.Replace("(", "( ").Replace(")", " )")
For index As Integer = expression.Length - 1 To 1 Step -1
Dim currentChar As String = expression(index)
'Check if the current character is a possible unary operator
If {"+", "-", "*", "/", "^"}.Contains(currentChar) Then
'If it is an operator check if the prior character that's not a whitespace is NOT an operator
Dim tempSource As String = expression.Substring(0, index).Replace(" ", String.Empty)
'If the character before the current one is an operator too, then we have a unary operator
If Not {"+", "-"}.Contains(tempSource(index - (expression.Substring(0, index).Length - tempSource.Length)
'So if the prior character is not a unary operator, add a space after it
expression = expression.Insert(index + 1, " ")
End If
'Regardless of if the operator is a unary operator or not add a space before it
expression = expression.Insert(index, " ")
End If
Next
'Return the string with no excess whitespace
Return String.Join(" ", expression.Split(New Char() {}, StringSplitOptions.RemoveEmptyEntries))
End Function