As the name indicates, the filter function is good for examining elements of a list for a certain property. Only elements which possess the property are allowed through the filter.
A filtering function applies a predicate (boolean function) on every element of a list. Only elements on which the predicate returns true are returned from the filtering function.
The function filter is not an essential Scheme function - but is part of the LAML general library
Filtering a list with a predicate f. The resulting list is the subset of the elements which satisfy f (the elements on which f returns true).