NAME

FP::Abstract::Pure - functional purity protocol

SYNOPSIS

use FP::List;
my $v= list(1); # or any other data structure that implements
                # FP::Abstract::Pure
is UNIVERSAL::isa($v, "FP::Abstract::Pure"), 1;
# Or use Safe::Isa instead of UNIVERSAL::isa, but I don't understand
# why overriding isa is useful (why fake inherit as opposed to real
# inheriting but then shadowing what needs to be shadowed? NEXT method
# and that needs to be supported in mock classes? TODO figure out.)

# but usually:
use FP::Predicates;
is_pure ($v) # true if $v is (officially) immutable, detectable from
             # inheritance of FP::Abstract::Pure or other means

DESCRIPTION

Base class for all data structures that don't allow mutation (by ordinary programs), i.e. are persistent (1).

(1) as in https://en.wikipedia.org/wiki/Persistent_data_structure

More precisely, those objects that don't have methods that when called make other methods non-functions.