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Merge branch 'slides/135-break-050_array_types-into-chapters' into 'master'
Resolve "Break 050_array_types into chapters" Closes #135 See merge request feng/training/material!201
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‎courses/fundamentals_of_ada/050_array_types.rst‎

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‎courses/fundamentals_of_ada/050_array_types/01-introduction.rst‎

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==============
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Introduction
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==============
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--------------
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Introduction
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--------------
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* Traditional array concept supported to any dimension
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.. code:: Ada
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declare
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type Hours is digits 6;
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type Days is (Mon, Tue, Wed, Thu, Fri, Sat, Sun);
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type Schedule is array (Days) of Hours;
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Workdays : Schedule;
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begin
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...
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Workdays (Mon) := 8.5;
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-------------
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Terminology
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-------------
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* :dfn:`Index type`
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- Specifies the values to be used to access the array components
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* :dfn:`Component type`
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- Specifies the type of values contained by objects of the array type
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- All components are of this same type
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.. code:: Ada
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type Array_T is array (Index_T) of Component_T;
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------------------------------
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Array Type Index Constraints
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------------------------------
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* Must be of an integer or enumeration type
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* May be dynamic
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* Default to predefined `Integer`
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- Same rules as for-loop parameter default type
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* Allowed to be null range
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- Defines an empty array
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- Meaningful when bounds are computed at run-time
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* Used to define constrained array types
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.. code:: Ada
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type Schedule is array (Days range Mon .. Fri) of Float;
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type Flags_T is array (-10 .. 10) of Boolean;
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* Or to constrain unconstrained array types
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.. code:: Ada
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subtype Line is String (1 .. 80);
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subtype Translation is Matrix (1..3, 1..3);
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-------------------------
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Run-Time Index Checking
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-------------------------
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* Array indices are checked at run-time as needed
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* Invalid index values result in :ada:`Constraint_Error`
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.. code:: Ada
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procedure Test is
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type Int_Arr is array (1..10) of Integer;
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A : Int_Arr;
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K : Integer;
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begin
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A := (others => 0);
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K := FOO;
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A (K) := 42; -- run-time error if Foo returns < 1 or > 10
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Put_Line (A(K)'Image);
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end Test;
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----------------------
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Kinds of Array Types
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----------------------
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* :dfn:`Constrained` Array Types
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- Bounds specified by type declaration
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- **All** objects of the type have the same bounds
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* :dfn:`Unconstrained` Array Types
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- Bounds not constrained by type declaration
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- Objects share the type, but not the bounds
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- More flexible
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.. code:: Ada
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type Unconstrained is array (Positive range <>)
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of Integer;
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U1 : Unconstrained (1 .. 10);
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S1 : String (1 .. 50);
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S2 : String (35 .. 95);
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‎courses/fundamentals_of_ada/050_array_types/02-constrained_array_types.rst‎

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=========================
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Constrained Array Types
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=========================
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-------------------------------------
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Constrained Array Type Declarations
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-------------------------------------
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* Syntax
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.. code:: Ada
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constrained_array_definition ::=
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array index_constraint of subtype_indication
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index_constraint ::= (discrete_subtype_definition
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{, discrete_subtype_indication})
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discrete_subtype_definition ::=
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discrete_subtype_indication | range
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subtype_indication ::= subtype_mark [constraint]
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range ::= range_attribute_reference |
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simple_expression .. simple_expression
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* Examples
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.. code:: Ada
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type Full_Week_T is array (Days) of Float;
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type Work_Week_T is array (Days range Mon .. Fri) of Float;
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type Weekdays is array (Mon .. Fri) of Float;
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type Workdays is array (Weekdays'Range) of Float;
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----------------------------------
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Multiple-Dimensioned Array Types
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----------------------------------
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.. container:: columns
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.. container:: column
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* Declared with more than one index definition
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- Constrained array types
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- Unconstrained array types
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* Components accessed by giving value for each index
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.. container:: column
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.. container:: latex_environment small
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.. code:: Ada
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type Three_Dimensioned is
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array (
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Boolean,
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12 .. 50,
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Character range 'a' .. 'z')
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of Integer;
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TD : Three_Dimensioned;
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...
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begin
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TD (True, 42, 'b') := 42;
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TD (Flag, Count, Char) := 42;
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-----------------------------
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Tic-Tac-Toe Winners Example
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-----------------------------
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.. container:: columns
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.. container:: column
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.. code:: Ada
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-- 9 positions on a board
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type Move_Number is range 1 .. 9;
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-- 8 ways to win
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type Winning_Combinations is
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range 1 .. 8;
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-- need 3 positions to win
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type Required_Positions is
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range 1 .. 3;
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Winning : constant array (
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Winning_Combinations,
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Required_Positions)
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of Move_Number := (1 => (1,2,3),
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2 => (1,4,7),
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...
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.. container:: column
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.. list-table::
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:width: 55%
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* - :superscript:`1` **X**
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- :superscript:`2` **X**
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- :superscript:`3` **X**
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* - :superscript:`4`
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- :superscript:`5`
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- :superscript:`6`
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* - :superscript:`7`
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- :superscript:`8`
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- :superscript:`9`
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* -
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-
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-
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* - :superscript:`1` **X**
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- :superscript:`2`
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- :superscript:`3`
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* - :superscript:`4` **X**
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- :superscript:`5`
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- :superscript:`6`
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* - :superscript:`7` **X**
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- :superscript:`8`
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- :superscript:`9`
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* -
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-
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-
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* - :superscript:`1` **X**
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- :superscript:`2`
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- :superscript:`3`
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* - :superscript:`4`
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- :superscript:`5` **X**
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- :superscript:`6`
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* - :superscript:`7`
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- :superscript:`8`
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- :superscript:`9` **X**
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------
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Quiz
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------
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.. code:: Ada
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type Array1_T is array (1 .. 8) of Boolean;
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type Array2_T is array (0 .. 7) of Boolean;
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X1, Y1 : Array1_T;
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X2, Y2 : Array2_T;
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.. container:: columns
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.. container:: column
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Which statement(s) is (are) legal?
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A. :answermono:`X1 (1) := Y1 (1);`
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B. :answermono:`X1 := Y1;`
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C. :answermono:`X1 (1) := X2 (1);`
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D. ``X2 := X1;``
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.. container:: column
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.. container:: animate
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Explanations
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A. Legal - elements are :ada:`Boolean`
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B. Legal - object types match
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C. Legal - elements are :ada:`Boolean`
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D. Although the sizes are the same and the elements are the same, the type is different
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