Conditional structures: Difference between revisions
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→case without a default: the error discussed isn’t syntactic
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{{Control Structures}}
[[Category:Simple]]
[[Category:Flow control]]
;Task:
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);</syntaxhighlight>
====case expressions====
Using the same example above, we assume that the
<syntaxhighlight lang="ada">Result := (case Op is
Add => A + B,
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</syntaxhighlight>
Note: some websites (particularly [https://www.radford.edu/nokie/classes/320/abe/operators.html#:~:text=if%20and%20case-,Examples%3A,1%2C%20others%20%3D%3E%200)%3B this one]) contain a different variant of a case expression (<syntaxhighlight lang="ada">case Op of...</syntaxhighlight>). The Ada Reference Manual indicates this is incorrect, and we use the [http://www.ada-auth.org/standards/12rm/html/RM-4-5-7.html formal version] here.
===case with a default alternative===
<syntaxhighlight lang="ada">type Days is (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday);
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===case without a default===
When there is no '''when others''' clause, the compiler will complain about any uncovered alternative. This defends against a common reason for bugs in other languages.
I.e., the following code is
<syntaxhighlight lang="ada">case Today is
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end case;</syntaxhighlight>
The
<syntaxhighlight lang="ada">case Today is
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}}
</syntaxhighlight>
=={{header|RPL}}==
'''IF..THEN'''
'''IF''' <instruction(s)> '''THEN''' <instruction(s)> '''END'''
'''IF..THEN..ELSE'''
'''IF''' <instruction(s)> '''THEN''' <instruction(s)> '''ELSE''' <instruction(s)> '''END'''
Instructions between <code>IF</code> and <code>THEN</code> are not mandatory, but recommended for lisibility. The interpreter considers <code>IF</code> as a null word and performs branching when meeting the word <code>THEN</code>: if stack level 1 is not equal to zero, the instructions between <code>THEN</code> and <code>END</code> will be executed.
<code>IFT</code> and <code>IFTE</code> are stack-based conditonal structures. <code>IFT</code> evaluates the content of stack level 1 only if the content of stack level 2 is not zero, otherwise it is dropped. <code>IFTE</code> evaluates the content of stack level 1 if the content of stack level 2 is zero, otherwise if evaluates the content of stack level 2.
'''CASE..END'''
'''CASE'''
<instruction(s)> '''THEN''' <instruction(s)> '''END'''
<instruction(s)> '''THEN''' <instruction(s)> '''END'''
<span style="color:grey">@ as many branches as needed</span>
<instruction(s)> <span style="color:grey">@ default branch (optional)</span>
'''END'''
=={{header|Ruby}}==
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