Split 020_declarations into modules

courses/fundamentals_of_ada/020_declarations/01-introduction.rst

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+==============
+Introduction
+==============
+
+----------------
+Ada Type Model
+----------------
+
+* Each :dfn:`object` is associated a :dfn:`type`
+* **Static** Typing
+
+   - Object type **cannot change**
+   - ... but run-time polymorphism available (OOP)
+
+* **Strong** Typing
+
+   - **Compiler-enforced** operations and values
+   - **Explicit** conversions for "related" types
+   - **Unchecked** conversions possible
+
+* Predefined types
+* Application-specific types
+
+    - User-defined
+    - Checked at compilation and run-time
+
+------------
+Declarations
+------------
+
+* :dfn:`Declaration` associates a :dfn:`name` to an :dfn:`entity`
+
+    - Objects
+    - Types
+    - Subprograms
+    - et cetera
+
+* In a :dfn:`declarative part`
+* Example: :ada:`N : Type := Value;`
+
+    - ``N`` is usually an :dfn:`identifier`
+
+* Declaration **must precede** use
+* **Some** implicit declarations
+
+    - **Standard** types and operations
+    - **Implementation**-defined
+

courses/fundamentals_of_ada/020_declarations/02-identifiers_and_comments.rst

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+==========================
+Identifiers and Comments
+==========================
+
+-----------
+Identifiers
+-----------
+
+.. image:: identifier_flow.png
+   :width: 60%
+
+.. container:: columns
+
+ .. container:: column
+
+   * Legal identifiers
+
+      .. code:: Ada
+
+         Phase2
+         A
+         Space_Person
+
+ .. container:: column
+
+   * Not legal identifiers
+
+      .. code:: Ada
+
+         Phase2__1
+         A_
+         _space_person
+
+* Character set **Unicode** 4.0
+* Case **not significant**
+
+   - `SpacePerson` |equivalent| `SPACEPERSON`
+   - ...but **different** from `Space_Person`
+
+* Reserved words are **forbidden**
+
+----------------
+Reserved Words
+----------------
+
+.. code:: Ada
+
+   abort          else              null               reverse
+   abs            elsif             of                 select
+   abstract (95)  end               or                 separate
+   accept         entry             others             some (2012)
+   access         exception         out                subtype
+   aliased (95)   exit              overriding (2005)  synchronized (2005)
+   all            for               package            tagged (95)
+   and            function          parallel (2022)    task
+   array          generic           pragma             terminate
+   at             goto              private            then
+   begin          if                procedure          type
+   body           in                protected (95)     until (95)
+   case           interface (2005)  raise              use
+   constant       is                range              when
+   declare        limited           record             while
+   delay          loop              rem                with
+   delta          mod               renames            xor
+   digits         new               requeue (95)
+   do             not               return
+
+----------
+Comments
+----------
+
+* Terminate at end of line (i.e., no comment terminator sequence)
+
+   .. code:: Ada
+
+      -- This is a multi-
+      -- line comment
+      A : B; -- this is an end-of-line comment
+
+----------------------------------------------
+Declaring Constants / Variables (simplified)
+----------------------------------------------
+
+* An :dfn:`expression` is a piece of Ada code that returns a **value**.
+
+.. code:: Ada
+
+   <identifier> : constant := <expression>;
+   <identifier> : <type> := <expression>;
+   <identifier> : constant <type> := <expression>;
+
+------
+Quiz
+------
+
+Which statement(s) is (are) legal?
+
+   A. ``Function : constant := 1;``
+   B. :answermono:`Fun_ction : constant := 1;`
+   C. ``Fun_ction : constant := --initial value-- 1;``
+   D. ``Integer Fun_ction;``
+
+.. container:: animate
+
+   Explanations
+
+   A. :ada:`function` is a reserved word
+   B. Correct
+   C. Cannot have inline comments
+   D. C-style declaration not allowed
+

courses/fundamentals_of_ada/020_declarations/03-literals.rst

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+==========
+Literals
+==========
+
+-----------------
+String Literals
+-----------------
+
+* A :dfn:`literal` is a *textual* representation of a value in the code
+
+.. code:: Ada
+
+   A_Null_String : constant String := "";
+      -- two double quotes with nothing inside
+   String_Of_Length_One : constant String := "A";
+   Embedded_Single_Quotes : constant String
+                          := "Embedded 'single' quotes";
+   Embedded_Double_Quotes : constant String
+                          := "Embedded ""double"" quotes";
+
+.. container:: speakernote
+
+   Note that the last example literal (that has embedded double quotes) is not an example of concatenation!
+
+--------------------------
+Decimal Numeric Literals
+--------------------------
+
+* Syntax
+
+   .. code::
+
+      decimal_literal ::=
+        numeral [.numeral] E [+numeral|-numeral]
+      numeral ::= digit {['_'] digit}
+
+* Underscore is not significant
+* **E** (exponent) must always be integer
+* Examples
+
+   .. code:: Ada
+
+      12      0       1E6         123_456
+      12.0    0.0     3.14159_26  2.3E-4
+
+------------------------
+Based Numeric Literals
+------------------------
+
+.. code::
+
+   based_literal ::= base # numeral [.numeral] # exponent
+   numeral ::= base_digit { '_' base_digit }
+
+* Base can be 2 .. 16
+* Exponent is always a base 10 integer
+
+   ::
+
+      16#FFF#           => 4095
+      2#1111_1111_1111# => 4095 -- With underline
+      16#F.FF#E+2       => 4095.0
+      8#10#E+3          => 4096 (8 * 8**3)
+
+--------------------------------------------
+Comparison to C's Based Literals
+--------------------------------------------
+
+* Design in reaction to C issues
+* C has **limited** bases support
+
+   - Bases 8, 10, 16
+   - No base 2 in standard
+
+* Zero-prefixed octal :code:`0nnn`
+
+   - **Hard** to read
+   - **Error-prone**
+
+------
+Quiz
+------
+
+Which statement(s) is (are) legal?
+
+   A. :answermono:`I : constant := 0_1_2_3_4;`
+   B. ``F : constant := 12.;``
+   C. ``I : constant := 8#77#E+1.0;``
+   D. ``F : constant := 2#1111;``
+
+.. container:: animate
+
+   Explanations
+
+   A. Underscores are not significant - they can be anywhere (except first and last character, or next to another underscore)
+   B. Must have digits on both sides of decimal
+   C. Exponents must be integers
+   D. Missing closing \#
+