Converting to Morse Code in Ada - arrays

Question

I posted the other day here because I was confused behind the syntax of Fortran and got an answer that helped a lot. But now I'm stuck in the same pickle, but with Ada this time.
Below is the gist of my program. I'm trying to read a sentence from the user and convert each character in it into morse code.
with Ada.Text_IO;
with Ada.Strings;
with Ada.Strings.Unbounded;
with Ada.Strings.Unbounded;
with Ada.Command_Line;
use Ada.Text_IO;
procedure MorseCode is
tempSentence : array(1 .. 20) of string;
last : Integer;
size : Integer;
i : Integer;
begin
Put("Enter the size of your sentence: ");
Get(size);
Put("Enter the sentence you would like to convert to morse code: ");
Get_Line(tempSentence, last);
Put_Line(tempSentence);
While_Loop :
while i < size loop
if tempSentence(i .. i) = 'A' or tempSentence(i) = 'a' then
Put(".- ");
elsif tempSentence(i .. i) = 'B' or tempSentence(i) = 'b' then
Put("-... ");
elsif tempSentence(i) = 'C' or tempSentence(i) = 'c' then
Put("-.-. ");
end if;
end loop While_Loop;
end;

Answer 1

I probably shouldn't, but the problems here go far beyond simple syntax errors so here's a few pointers to a more Ada-like approach.
Words in bold are worth reading about in more detail in a good Ada book.
First, stop thinking at such a low level. Strings are arrays of characters, and arrays in Ada offer facilities such as array attributes to make programming simpler - and especially program maintenance.
Arrays are fixed in length when you create them, but that length doesn't have to be determined until then. So you can declare an array and initialise it with a function call - it takes its size from the result of the function call.
Use this facility and eliminate size as a separate thing altogether.
When the declare block ends, the array goes out of scope, so it's freed automatically, and if it's in a loop, the function call can return a different size string, so the array bounds can be different each time - to problem.
We need to loop over all characters in the array, but we don't know its size ... so just ask it, for example via its range attribute.
And rather than writing every test twice, use a function from the Ada.Characters.Handling package to ensure we only hve to deal with lower case.
Also, if statements are a poor choice for this task, a case statement is simpler and shorter - I've shown both below
with Ada.Text_IO;
use Ada.Text_IO;
with Ada.Characters.Handling;
procedure MorseCode is
begin
Put("Enter the sentence you would like to convert to morse code: ");
declare
Sentence : String := Get_Line;
begin
Put_Line(Sentence);
for i in Sentence'range loop
if Ada.Characters.Handling.To_Lower(Sentence(i)) = 'a' then
Put(".- ");
-- elsif etc ... not very nice
end if;
case Ada.Characters.Handling.To_Lower(Sentence(i)) is
when 'b' => Put("-...");
when 'c' => Put("-.-.");
when others => null;
end case;
end loop;
end;
end;
There are also bounded and unbounded strings which you don't need in this simple example. They are a little tedious to use sometimes, you need type conversions between them and plain Strings.