Sum (Arraylist function): Difference between revisions

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<ul>
<ul>
<li>The optional <var class="term">method</var> parameter lets you further manipulate the <var>Arraylist</var> item values
<li>The optional <var class="term">method</var> parameter lets you further manipulate the <var>Arraylist</var> item values
before performing the <var>Sum</var> method's operation.
before calculating the sum. The <var class="term">method</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">method</var> function that can map the item values to intrinsic values.
If your <var>Arraylist</var>'s items are not intrinsic values, you must specify a function that can map the item values to intrinsic values or the method will fail.
<p>  
<p>  
For example, for an <var>Arraylist</var> that is a list of coordinates, you could
For example, for an <var>Arraylist</var> that is a list of coordinates, you could

Revision as of 15:20, 19 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.
method 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 method value is the special identity function, This, which simply returns the item value.

Usage notes

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