converting to char

[Anti-Rich]

hi guys

just wondering, i am using a function to determine if there are any non-numerical characters in the string as the user inputs a payrate. (the only exception being the . character.

the question i have is, i have used a way to convert a string to char as follows..

"."c

that little c converts it to char for use in the if statement. now, i know i can also use cchar("."), i was just wondering is either way better than the other. and also, is there another way i could be doing it?

cheers all
adam

 

[Raven65]

You could use Regular Expressions [MSDN] to check the string for anything not 0-9 or a "."

 

[Anti-Rich]

this is the function i use...

private function returntext(byval t as string) as string
dim temp as string=""
for i as integer=0 to t.length-1
        if Char.isnumeric(t.chars(i)) or t.chars(i) = "."c
        temp &= t.chars(i)
end if
 
next
return temp
end function

what do you think?

 

[jmcilhinney]

The little c does NOT convert anything to a Char. Using the little c suffix means that the literal IS a Char. Doing this:

Dim myChar As Char = "."c

simply creates a Char literal and assigns it to the myChar variable. There are no Strings involved. Doing this:

Dim myChar As Char = CChar(".")

creates a String literal, then converts that to a Char and assigns it to the variable. It creates a String object for nothing.

 

[cjard]

Concur with JMc.. example, in a C-flavoured language you have:

char c = 'a';

in vb, that's:

Dim c as char = "a"c

because ' is used for comment


Raven mentions regex. the following regex checks that only a (maybe decimal) number is entered:

System.Text.RegularExpressions.Regex.IsMatch(input, "[0-9]+([.][0-9]+)?")

broken down:
"[0-9]+([.][0-9]+)?"
[0-9]+ = one or more occurrance of 0 to 9
( = open a group
[.] = followed by .
[0-9]+ = see above
)? = close group, and allow 0 or 1 of the group


BUt you know what? all this is so much harder than just trying to convert it to a decimal and noting the fail:

Dim d as Decimal
If Decimal.TryParse(input, d) Then
  'thankyou for your correct input
Else
  'your input was not a number
Endif

 

[Anti-Rich]

ok i think i get it. so using the c like "."c simply means that it IS a char...

so why would people ever bother using cchar(".") if its doing something thats unnecessary? or im i missing something, because it seems that using the little c is much quicker than converting it, as using the c simply means that it is a char (therefore avoiding both conversion and creation of unnecessary string).

does that sound right?

cheers for your feedback guys

 

[JohnH]

The "A"c convension is very limited, in that it will only work with a typed string of exactly one character, it won't work with "AA"c. You can't make a string variable 'myA' set it to "A" and do 'myChar=myAc' and expect that 'c' to be understood as anything special, you'd have to write 'myChar=cchar(myA)'.

 

[Anti-Rich]

im not sure i understand what you mean... i always thought when you are using a char it was SUPPOSED to be one character and one character only

cheers for your feedback as well

 

[JohnH]

Sometimes one hardcode these characters and it is a shortcut just writing the "A" string and specifically denote it to be interpreted as a Char type.

 

[Anti-Rich]

ok, but if you do it what i would perceive to be the 'right way' it would be like this...

Private c as Char = "c"

so doesnt then create another unnecessary string? wouldnt it be better for the value (in this case "c") to be iterpreted straightaway as a char?

sorry if it sounds dumb, but im a bit lost at the moment *sheepish grin*

 

[JohnH]

You don't understand, "A" is a String, "A"c is a Char.
Create a new project, turn Option Strict on and try to code sloppy like this:

Dim c As Char = "A"

You'll get this error:

Option Strict On disallows implicit conversions from 'String' to 'Char'.

You could access by index the first character in that string like this:

Dim c As Char = "A"(0)

..which goes fine with strict type code, but "A"c denotion is easier.

 

[Anti-Rich]

ok,

so if i was to instead use

Private f as Char = "f"c


taht error wouldnt happen due to the fact it is being interpreted (the 'f') as a char from the get-go

is that correct?

 

[JohnH]

That is just so totally correct.

 

[Anti-Rich]

ah ok, cheers for your help. glad i got it (finally) hahah

have a good one mate

regards
adam