chart-object-id-equality-test

Arguments: chart-or-plot

Returns the value of the chart-object-id-equality-test property of a chart-or-plot. The value may be set at creation time by passing the :chart-object-id-equality-test initarg, or any time later by calling (setf chart-object-id-equality-test).

The value of this property is a function (or the name of a function) that should return true if two chart object ID's are equivalent. The function is used whenever a chart value is being looked up from its object ID, to test whether each ID is the one that is sought.

The default value is equal, which should suffice for all ordinary types of chart object ID's such as symbols, numbers, and strings. If all of the ID's are symbols, for example, then it may improve efficiency a bit to specify eq as the value of this property.

Chart object IDs are established by the chart-objects property.

See also chart-item-id-equality-test.

See chart-widget, plot-widget, and also cg-chart-widget.htm.

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Created 2010.1.21.