Ada Strings Libraries for the clueless.

Ada Strings Libraries for the clueless.

[Caffeine Junky]

Recently I've actually taken the time to peruse the Ada.Strings section
of the Ada LRM. Lot's of nifty functions there, although I'm somewhat
fuzzy on what exactly they do. Probably because I havent bothered to play
with Strings at all until recently. Example..

Ada.Strings.Fixed

	function Index (Source : in String; Pattern : in String;
				 Going : in Direction := Forward;
				 Mapping : in Maps.Character_Mapping := Maps.Identity)
	return Natural;


Now, the gist of this function is pretty clear. It looks at a String and
returns the number of how many Characters are in the string(I'm
assuming.) But what's this "Pattern" string I'm supposed to pass to it? 
Does it only count the characters in the String that match the Pattern given
in the Pattern variable?

Now, to be fair, %95 of this section of the LRM is self-explanatory and
pretty simple to understand. I'm just running into a few things here and
there that are somewhat ambiguous. Or maybe I'm just dim-witted or low on
Caffiene at the moment.

Note: I'm focusing on the Strings libraries at the moment cause I'm
teaching myself to write very stable and fast buffers/pipes specifically
for text. "But Junky, why not make them generic buffers for everything?"
Because that's not what I'm doing right now. Heh.

I dont really need a tutorial on this, just a quick run down on what
these functions are really asking for.

Any pointers would be appreciated.

Caffiene Junky
Caffinated Corps.

Re: Ada Strings Libraries for the clueless.

[Mark Biggar]

Caffeine Junky wrote:
> Recently I've actually taken the time to peruse the Ada.Strings section
> of the Ada LRM. Lot's of nifty functions there, although I'm somewhat
> fuzzy on what exactly they do. Probably because I havent bothered to play
> with Strings at all until recently. Example..
> 
> Ada.Strings.Fixed
> 
> 	function Index (Source : in String; Pattern : in String;
> 				 Going : in Direction := Forward;
> 				 Mapping : in Maps.Character_Mapping := Maps.Identity)
> 	return Natural;
> 
> 
> Now, the gist of this function is pretty clear. It looks at a String and
> returns the number of how many Characters are in the string(I'm
> assuming.) But what's this "Pattern" string I'm supposed to pass to it? 
> Does it only count the characters in the String that match the Pattern given
> in the Pattern variable?

No, it searchs the string Source for the leftmost occurence of a
substring that is equal to Pattern and returns the index of the
start of that substring.

-- 
Mark Biggar
mark.a.biggar@attbi.com

Re: Ada Strings Libraries for the clueless.

[Simon Wright]

Caffeine Junky <nospam@hotmail.com> writes:

> Ada.Strings.Fixed
> 
> 	function Index (Source : in String; Pattern : in String;
> 				 Going : in Direction := Forward;
> 				 Mapping : in Maps.Character_Mapping := Maps.Identity)
> 	return Natural;
> 
> 
> Now, the gist of this function is pretty clear. It looks at a String
> and returns the number of how many Characters are in the string(I'm
> assuming.) But what's this "Pattern" string I'm supposed to pass to
> it?  Does it only count the characters in the String that match the
> Pattern given in the Pattern variable?

If you read on to (58) you find

    Each Index function searches for a slice of Source, with length
    Pattern'Length, that matches Pattern with respect to Mapping; the
    parameter Going indicates the direction of the lookup. If Going =
    Forward, then Index returns the smallest index I such that the
    slice of Source starting at I matches Pattern. If Going =
    Backward, then Index returns the largest index I such that the
    slice of Source starting at I matches Pattern. If there is no such
    slice, then 0 is returned. If Pattern is the null string then
    Pattern_Error is propagated.

which seems pretty clear :-)   (except perhaps the Mapping part)

Re: Ada Strings Libraries for the clueless.

[Jeffrey Creem]

"Caffeine Junky" <nospam@hotmail.com> wrote in message
news:eVWx9.26421$Lu1.39570@sccrnsc01...


stuff deleted

> Ada.Strings.Fixed
>
> function Index (Source : in String; Pattern : in String;
> Going : in Direction := Forward;
> Mapping : in Maps.Character_Mapping := Maps.Identity)
> return Natural;
>
>
> Now, the gist of this function is pretty clear. It looks at a String and
> returns the number of how many Characters are in the string(I'm
> assuming.) But what's this "Pattern" string I'm supposed to pass to it?


Number of characters in the string is just the 'length of the string.
(Others have explained what this function actually does so I won't repeat
it)