Sum (Arraylist function): Difference between revisions

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{{Template:Arraylist:Sum subtitle}}
{{Template:Arraylist:Sum subtitle}}


This page is [[under construction]].
==Syntax==
==Syntax==
{{Template:Arraylist:Sum syntax}}
{{Template:Arraylist:Sum syntax}}
===Syntax terms===
===Syntax terms===
<table class="syntaxTable">
<table class="syntaxTable">
<tr><th>%sum</th><td>number</td></tr>
<tr><th>%sum</th>
<td>A <var>Float</var> variable to contain the numeric result.</td></tr>
 
<tr><th>al</th>
<tr><th>al</th>
<td>Arraylist object</td></tr>
<td>An <var>Arraylist</var> object.</td></tr>
<tr><th>method</th>
 
<td><var>ItemFunction</var> object</td></tr>
<tr><th>itemFunction</th>
<td>A function that operates on the type of the items in the <var>Arraylist</var>. It may be a [[Local and Common entities#Defining and invoking a local method|local method]] or [[Method variables|method variable]] or a class member (<var>Variable</var>, <var>Property</var>), and it must return an [[Intrinsic classes|intrinsic]] (probably <var>Float</var>) value.
<p>
The default <var class="term">itemFunction</var> value is the special identity function, <var>[[Collections#Using the This function as the Maximum parameter|This]]</var>, which simply returns the item value.</p></td></tr>
</table>
</table>
==Usage notes==
==Usage notes==
<ul>
<li>The optional <var class="term">itemFunction</var> parameter lets you further manipulate the <var>Arraylist</var> item values
before calculating the sum. The <var class="term">itemFunction</var> default (identity function <var>This</var>) fails against non-intrinsic values, however. If your collection items are <i>not</i> intrinsic values, you must specify an <var class="term">itemFunction</var> function that can map the item values to intrinsic values.
<p>
For example, for an <var>Arraylist</var> that is a list of coordinates, you could
return the sum of their distance from the origin by first applying a local function as the <var>Sum</var> method's <var class="term">itemFunction</var> parameter: </p>
<p class="code">b
class point
    public
      constructor new(%x is float, %y is float)
      variable x is float
      variable y is float
    end public
    constructor new(%x is float, %y is float)
      %this:x = %x
      %this:y = %y
    end constructor
end class
local function (point):distance is float
  return (%this:x * %this:x + %this:y * %this:y):[[SquareRoot (Float function)|squareRoot]]
end function
%al is arrayList of object point
%al = new
%al:add(new(1,1))
%al:add(new(3,4))
%al:add(new(-5,12))
print %al:sum(distance)
end
</p>
The result is <code>19.4142135623731</code>. </ul>
==Examples==
==Examples==
<p class="code">b
%al is arrayList of float
%al = new
%al = [[List (Arraylist function)|list]](5, 3, 8)
print %al:sum
end
</p>
The result is:
<p class="output">16
</p>
==See also==
==See also==
{{Template:Arraylist:Sum footer}}
{{Template:Arraylist:Sum footer}}

Latest revision as of 16:49, 27 July 2012

Compute the sum of the items (Arraylist class)

[Introduced in Sirius Mods 7.8]


Syntax

%sum = al:Sum[( [itemFunction])]

Syntax terms

%sum A Float variable to contain the numeric result.
al An Arraylist object.
itemFunction A function that operates on the type of the items in the Arraylist. It may be a local method or method variable or a class member (Variable, Property), and it must return an intrinsic (probably Float) value.

The default itemFunction value is the special identity function, This, which simply returns the item value.

Usage notes

  • The optional itemFunction parameter lets you further manipulate the Arraylist item values before calculating the sum. The itemFunction default (identity function This) fails against non-intrinsic values, however. If your collection items are not intrinsic values, you must specify an itemFunction function that can map the item values to intrinsic values.

    For example, for an Arraylist that is a list of coordinates, you could return the sum of their distance from the origin by first applying a local function as the Sum method's itemFunction parameter:

    b class point public constructor new(%x is float, %y is float) variable x is float variable y is float end public constructor new(%x is float, %y is float) %this:x = %x %this:y = %y end constructor end class local function (point):distance is float return (%this:x * %this:x + %this:y * %this:y):squareRoot end function %al is arrayList of object point %al = new %al:add(new(1,1)) %al:add(new(3,4)) %al:add(new(-5,12)) print %al:sum(distance) end

    The result is 19.4142135623731.

Examples

b %al is arrayList of float %al = new %al = list(5, 3, 8) print %al:sum end

The result is:

16

See also