CODEWITHSUNDEEP
adagnat
Claudio Ludovico Malorgio
Claudio Ludovico Malorgio

Reputation: 75

Ada - Trim and delete special Chars on strings

I have a variable called Input 

Input : STRING (1 .. 80) ;

I use Ada.Strings and Ada.Text_IO as library and I need to know if I can, and how, to remove spaces and special characters (such as the apex, the comma and period) on Input Variable.

Upvotes: 2

Views: 4743

Answers (3)

user571138
user571138

Reputation:

If you have Ada.Strings, you most likely have Ada.Strings.Fixed and Ada.Strings.Maps.

Use the Ada.Strings.Fixed.Translate method(s) with assistance from Ada.Strings.Maps to translate any characters to any other characters.

Alternatively you can just loop over your input string and only append characters that you want to a new string. (less elegant, but you dont need any other libraries)

Upvotes: 3

T.E.D.
T.E.D.

Reputation: 44804

Well, first off you have to understand that if you want to remove a character potentially from the middle of a string, all the characters after the removed character will have to be shifted over to the left one character. This isn't an Ada-specfic issue. If the string is big, this could be rather inefficient. I wouldn't call 80 characters or less "big" though.

The second thing you have to understand is that in Ada, unlike many languages, strings are meant to be perfectly-sized. That means that if you are going to use a String variable as a buffer (eg: for input via Text_IO), you are going to have to also keep track of the actual length of valid data in it with another variable.

Given that, it can be a simple matter of writing code to recognize the characters you don't want in there, and remove them with something like:

if (Bad_Index < Input_Length) then
    Input(Bad_Index .. Input_Length - 1) := Input(Bad_Index + 1 .. Input_Length);
end if;
Input_Length := Input_Length - 1;

However, this is kind of the hard way. If you really have a string you want to manipulate this way, it is probably easiest to put it in an unbounded string object. Ada.Strings.Unbounded.Find_Token and Ada.Strings.Unbounded.Delete will do what you need, and all you have to write is a loop around them.

Upvotes: 1

Marc C
Marc C

Reputation: 8522

The Ada.Strings.Maps packages would likely be very helpful here, particularly the "To_Set" (define the characters you want to strip out in a Character_Sequence) and "Is_In" functions.

Since you're deleting, rather than replacing, characters, you'll have to iterate through the string, checking to see whether each one "is in" the set of those to be deleted. If so, don't append it to the output string buffer.

Upvotes: 2

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