The pseudocode used in examples in Indra's Pearls are modelled largely after Maple. We didn't commit to precise working Maple, because we didn't want to get into the technical details of using Maple. Therefore, we didn't use the convenient and powerful list manipulating routines of Maple (such as map, select, op, etc.) because these will be dramatically different from one programming environment to another.
Here we shall indeed give some honest working Maple routines to implement the algorithms described in the book. We will sometimes give several versions to show how to use different programming constructs.