CODEWITHSUNDEEP
stringadabounded-types
Martel
Martel

Reputation: 2734

What is the best way for initializing a fixed-length string in Ada?

I want to initialize a fixed-length String in Ada more or less like following:

S : String (1..256) := ("Hello", others => Character'Val (0));

I obtain an error while trying to compile. Is there any way to achieve something similar to the above?

Upvotes: 4

Views: 1413

Answers (2)

Frédéric Praca
Frédéric Praca

Reputation: 1641

The reason your code does not compile is that String is an array of Character so the equivalent would be

s : String(1..256) := (1 => 'H',
                       2 => 'e',
                       3 => 'l',
                       4 => 'l',
                       5 => 'o',
                       others => Character'Val(0));

Which is clearly far from ideal.

Another way is to use the Move procedure in [Ada.Strings.Fixed][1].

Move(Target => s,
     Source => "Hello",
     Pad => Character'Val(0));

But this can't be done in the declaration.

Finally, this compiles :

s : String(1..256) := "Hello" & (6..256 => Character'Val(0));

But I find it less clear [1]: http://www.ada-auth.org/standards/rm12_w_tc1/html/RM-A-4-3.html

Upvotes: 5

Jeffrey R. Carter
Jeffrey R. Carter

Reputation: 3358

I would usually do something like

Hello : constant String := "Hello";

Desired_Length : constant := 256;

S : String := Hello & (1 .. Desired_Length - Hello'Length => Character'Val (0) );

or

(Hello'Length + 1 .. Desired_Length => ...);

Upvotes: 1

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