view release on metacpan or  search on metacpan

lib/FP/Predicates.pm  view on Meta::CPAN

    sub {
        my ($v) = @_;
        defined $v
            ? do {
            my $b = &$pred($v);
            $b or failwith [$b], "maybe"
            }
            : 1
    }
}

# (this would also be a candidate for FP::Ops)
sub is_defined {
    @_ == 1 or fp_croak_arity 1;
    defined $_[0] or fail "is_defined", $_[0]
}

sub is_true {
    @_ == 1 or fp_croak_arity 1;
    $_[0] or fail "is_true", $_[0]
}

# (this would also be a candidate as 'not' with a different name for
# FP::Ops)
sub is_false {
    @_ == 1 or fp_croak_arity 1;
    !$_[0] or fail "is_false", $_[0]
}

sub true {
    1
}

sub false {
    0
}

sub complement {
    @_ == 1 or fp_croak_arity 1;
    my ($f) = @_;
    sub {
        my $r = &$f(@_);
        !$r

            # XX: in a perfect world we would have information about
            # why $f *succeeded* here. Sigh. We don't. TODO?
            or failwith [fail "not"], "complement"
    }
}

TEST {
    my $t = complement(\&is_natural);
    [map { &$t($_) } (-1, 0, 1, 2, "foo")]
}
[1, 1, 0, 0, 1];

sub either {
    my (@fn) = @_;
    sub {
        # Meh, code it up all twice. Macros anyone?
        if ($FP::Failure::use_failure) {
            my @failures;
            for my $fn (@fn) {
                my $r = &$fn;
                return $r if $r;
                push @failures, $r
            }
            failwith \@failures, "either"
        } else {
            for my $fn (@fn) {
                my $r = &$fn;
                return $r if $r;
            }
            0
        }
    }
}

TEST {
    my $t = either \&is_natural, \&is_boolean;
    [map { &$t($_) } (-1, 0, 1, 2, "foo")]
}
[0, 1, 1, 2, 0];

sub all_of {
    my (@fn) = @_;
    sub {
        for my $fn (@fn) {
            my $r = &$fn;
            return failwith [$r], "all_of" unless $r;
        }
        1
    }
}

sub both {
    @_ == 2 or fp_croak_arity 2;
    all_of(@_)
}

1