Android Question Char = Int?

[wonder]

Why isn't it possible to perform arithmetic with chars and ints, without having to use the asc() function?

'Not legal
Dim d = "d" As Char
Dim a = d - 3 As Int

'Legal
Dim d = "d" As Char
Dim a = asc(d) - 3 As Int

Isn't char a primitive type?

 

[wonder]

How huge is the difference?

 

[sorex]

** Activity (main) Create, isFirst = true **
3431108 123456789
8888036 123456789
2707761 123456789
** Activity (main) Resume **


notice that the first and third are actually the same sub with just another name

 

[wonder]

Strange indeed...

 

[wonder]

Well, here's the best I could come-up with:

'Fast
Sub getInt(str As String) As Int
    Dim s = 0, v = 0, p = 1, i = str.Length - 1 As Int  
    Do While i > -1
        v = Asc(str.CharAt(i))
        If v = 45 Then
            s = -s
            Exit
        End If
        s = s + ((v - 48) * p)
        p = p * 10      
        i = i - 1      
    Loop
    Return s
End Sub

'Even faster
Sub getUnsignedInt(str As String) As Int
    Dim s = 0, p = 1, i = str.Length - 1 As Int
    Do While i > -1
        s = s + ((Asc(str.CharAt(i)) - 48) * p)
        p = p * 10
        i = i - 1
    Loop
    Return s
End Sub

Probably not really useful to anyone besides me...

 

[sorex]

you could move the - check outside the loop.

before the loop to set the right length (0 or -1)

and after to make it negative or not

but that causes 'overhead' aswell but only once.

 

[wonder]

Sure, why not?

'Fast
Sub getInt(str As String) As Int
    Dim s = 0, z = 0, p = 1, i = (str.Length - 1) As Int
    If Asc(str.CharAt(0)) = 45 Then p = -1 Else z = -1
    Do While i > z
        s = s + ((Asc(str.CharAt(i)) - 48) * p)
        p = p * 10   
        i = i - 1   
    Loop
    Return s
End Sub

 

[sorex]

excellent fix with that "pre-negativenizer"

 

[wonder]

Funny that, for some reason Asc(str.CharAt(0)) == 45 is faster than str.CharAt(0) == "".

 

[MaFu]

Funny that, for some reason Asc(str.CharAt(0)) == 45 is faster than str.CharAt(0) == "".

First is comparing two character codes, second is a string compare (more overhead).