View source for And and Or (SelectionCriterion functions)

{{Template:SelectionCriterion:And and Or subtitle}}

These [[Notation conventions for methods#Shared members|shared methods]] each create a new <var>SelectionCriterion</var> object
that is an expression used to select the items in a collection.
Each function uses a different logical operator
to form an expression that combines one or more <var>SelectionCriterion</var> objects.

An <var>Or</var> criterion returns true for a collection item if any of the
component <var>SelectionCriterion</var> expressions are true for the item;
otherwise it returns false.
An <var>And</var> criterion returns true if all of the
component <var>SelectionCriterion</var> expressions are true for the item;
otherwise it returns false.

The [[Collections#Searching a collection|collection searching method]]
that makes use of a <var>SelectionCriterion</var> specifies:
<ul>
<li>Whether to return the first item or item number or all items that satisfy the
selection criterion.
<li>Where in the collection to begin searching.
</ul>
==Syntax==
{{Template:SelectionCriterion:And syntax}}
{{Template:SelectionCriterion:Or syntax}}

===Syntax terms===
<table class="syntaxTable">
<tr><th>%selectionCriterion</th>
<td>A <var>SelectionCriterion</var> object variable to contain the new object instance. </td></tr>
<tr><th nowrap="true"><var>[%(SelectionCriterion For </var>itemType<var>)]</var>
<td>This optional specification of the class in parentheses denotes a [[Notation conventions for methods#Shared methods|virtual constructor]]. See [[#Usage notes|"Usage notes"]], below, for more information about invoking a <var>SelectionCriterion</var> virtual constructor. </td></tr>
<tr><th>list</th>
<td>A comma-separated list of one or more <var>SelectionCriterion</var> objects. </td></tr>

</table>

==Usage notes==
<ul>
<li>As described in [[Object variables#Virtual Constructor methods|"Virtual Constructor methods"]], <var>And</var> and <var>Or</var> can be invoked with
no method object, with an explicit class specification, or with an object variable of the class,
even if that object is <var>Null</var>:
<p class="code">%selCrit = And(<i>list</i>)

%selCrit = %(SelectionCriterion for float):Or(<i>list</i>)

%selCrit = %selCrit:And(<i>list</i>)
</p>
'''Note:'''
As shown in the second of these above, if you explicitly specify the
class name, you must include the item datatype of the collection to be searched, just as on a <var>SelectionCriterion</var> object variable's [[SelectionCriterion class#Declaring a SelectionCriterion object variable|declaration]].
<li>All <var>Or</var> and <var>And</var> <var>SelectionCriterion</var> conditions
are short-circuiting conditions.
That is, if any of the conditions in
an <var>Or</var> return True, the subsequent conditions are not evaluated and the
<var>Or</var> returns True.
Similarly, if any of the conditions in an <var>And</var> return
False, the subsequent conditions are not evaluated, and the <var>And</var> returns a
False.

Therefore, it is wise to put the most likely conditions first
in an <var>Or</var>, and it is wise to put the least likely first in an <var>And</var>.
For a mix
of conditions where some are simply variable references and others require
method evaluation, it probably is best to put the variable references
first, as these are probably much cheaper to evaluate.
</ul>

==Examples==
<ol>
<li>The following criterion
matches numbers less than 70 and greater than or equal to 95:
<p class="code">%sel = OR(lt(this,70), ge(this,95))
</p>
<li>The following criterion matches numbers that are
less than or equal to 33 but not 30:
<p class="code">%sel = AND(le(this, 33), ne(this,30)))
</p>
</ol>

==See also==
{{Template:SelectionCriterion:And and Or footer}}
[[Category:SelectionCriterion methods]]