Error fix: raised CONSTRAINT_ERROR : book1.adb:28 length check failed - ada

Question

What I'm trying to do with Ada is to create a Book object and then print out that book. Problem is, the language is not very writable. When I compile, build the main file, and then execute the file, it gives me this error:
raised CONSTRAINT_ERROR : book1.adb:28 length check failed
Here's what I have in the body file:
package body Book1 is
function getAuthor (B: in Book) return AuthorName is
begin
return B.getAuthor;
end getAuthor;
function getTitle (B: in Book) return TitleName is
begin
return B.getTitle;
end getTitle;
function getNumberOfPages (B: in Book) return Pages is
begin
return B.getNumberOfPages;
end getNumberOfPages;
function createBook (Author: in String; Title: in String; NumberOfPages: in Float)
return Book is
B: Book;
begin
B.getAuthor := Author;
B.getTitle := Title;
B.getNumberOfPages := NumberOfPages;
return B;
end createBook;
end Book1;
Here's what I have in the spec file:
package Book1 is
type Book is tagged private;
subtype AuthorName is String (1 .. 300);
subtype TitleName is String (1 .. 750);
subtype Pages is Float range 0.0 .. 5000000.0;
function getAuthor(B: in Book) return AuthorName;
function getTitle(B: in Book) return TitleName;
function getNumberOfPages(B: in Book) return Pages;
function createBook(Author: in String; Title: in String; NumberOfPages: in Float)
return Book;
private
type Book is tagged
record
getAuthor: AuthorName;
getTitle: TitleName;
getNumberOfPages: Pages;
end record;
end Book1;
Here's what I have in the test file:
with Book1, Ada.Text_IO, Ada.Float_Text_IO;
use Book1, Ada.Text_IO, Ada.Float_Text_IO;
procedure testBook is
theRealBook: Book := createBook(Author => "Jordan White",
Title => "The Last Christmas",
NumberOfPages => 32.0);
procedure Print_Book (B: in Book'Class) is
begin
Put (getAuthor (B => B));
Put (getTitle (B => B));
Put (getNumberOfPages (B => B));
New_Line;
end Print_Book;
begin
Print_Book (theRealBook);
end testBook;
What exactly am I doing to get this error, and how can I fix it?

Answer 1

Your statement here:
theRealBook: Book := createBook(Author => "Jordan White",
Title => "The Last Christmas",
NumberOfPages => 32.0);
Has an implicit length of strings for both author and title (String Literals).
This means that when you assign author and title here:
B.getAuthor := Author;
B.getTitle := Title;
You are making the assumption that "Jordan white" is a string of length 300. (Same problem for Title)
I Suspect this is homework, so ill leave it up to you to figure out how to find the length, and bounds of strings, and how to assign array slices.