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Slides/187 expressions membership tests quiz add information prior to quiz outlining usage of or #473

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71b1d3d
Better wording to describe sets
frank-at-adacore Dec 19, 2024
20adbf2
Clean up quiz answer explanation
frank-at-adacore Dec 19, 2024
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35 changes: 22 additions & 13 deletions courses/fundamentals_of_ada/080_expressions/02-membership_tests.rst
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Expand Up @@ -42,20 +42,29 @@ Testing Constraints Via Membership
Testing Non-Contiguous Membership
-----------------------------------

* Uses vertical bar "choice" syntax
* We use :ada:`in` to indicate membership in a range of values

.. code:: Ada
.. code:: Ada

if Color in Red .. Green then
if Index in List'Range then

* But what if the values are not contiguous?

* We could use a Boolean conjunction

.. code:: Ada

if Index = 1 or Index = 3 or Index = 5 then

* Or we could simplify it by specifying a collection (or set)

.. code:: Ada

if Index in 1 | 3 | 5 then

declare
M : Month_Number := Month (Clock);
begin
if M in 9 | 4 | 6 | 11 then
Put_Line ("31 days in this month");
elsif M = 2 then
Put_Line ("It's February, who knows?");
else
Put_Line ("30 days in this month");
end if;
* **|** is used to separate members
* So :ada:`1 | 3 | 5` is the set for which we are verifying membership

..
language_version 2012
Expand All @@ -81,7 +90,7 @@ Which condition(s) is (are) legal?

Explanations

A. To use :ada:`or`, both sides of the comparison must be duplicated (e.g. :ada:`Today = Mon or Today = Wed`)
A. :ada:`Wed` and :ada:`Fri` are not Boolean expressions - need to compare each of them to :ada:`Today`
B. Legal - should always return :ada:`True`
C. Legal - returns :ada:`True` if :ada:`Today` is :ada:`Sat` or :ada:`Sun`
D. Legal - returns :ada:`True` if :ada:`Today` is :ada:`Tue` or :ada:`Thu`
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