Funx.Predicate

Mix.install([
  {:funx, "0.8.4"}
])

Provides utility functions for working with predicates—functions that return true or false.

This module enables combining predicates in a declarative way using logical operations:

• p_and/2: Returns true if both predicates are true.
• p_or/2: Returns true if at least one predicate is true.
• p_not/1: Negates a predicate.
• p_all/1: Returns true if all predicates in a list are true.
• p_any/1: Returns true if any predicate in a list is true.
• p_none/1: Returns true if none of the predicates in a list are true.

These functions simplify complex conditional logic.

Function Examples

import Funx.Predicate

Examples

Combining predicates with p_and/2:

is_adult = fn person -> person.age >= 18 end
has_ticket = fn person -> person.tickets > 0 end
can_enter = p_and(is_adult, has_ticket)

can_enter.(%{age: 20, tickets: 1})

can_enter.(%{age: 16, tickets: 1})

Using p_or/2 for alternative conditions:

is_vip = fn person -> person.vip end
is_sponsor = fn person -> person.sponsor end
can_access_vip_area = p_or(is_vip, is_sponsor)

can_access_vip_area.(%{vip: true, sponsor: false})

can_access_vip_area.(%{vip: false, sponsor: false})

Negating predicates with p_not/1:

is_minor = fn person -> person.age < 18 end
is_adult = p_not(is_minor)

is_adult.(%{age: 20})

is_adult.(%{age: 16})

Using p_all/1 and p_any/1 for predicate lists:

is_adult = fn person -> person.age >= 18 end
has_ticket = fn person -> person.tickets > 0 end
conditions = [is_adult, has_ticket]
must_meet_all = p_all(conditions)
must_meet_any = p_any(conditions)

must_meet_all.(%{age: 20, tickets: 1})

must_meet_all.(%{age: 20, tickets: 0})

must_meet_any.(%{age: 20, tickets: 0})

must_meet_any.(%{age: 16, tickets: 0})

Using p_none/1 to reject multiple conditions:

is_adult = fn person -> person.age >= 18 end
is_vip = fn person -> person.vip end
cannot_enter = p_none([is_adult, is_vip])

cannot_enter.(%{age: 20, vip: true})

cannot_enter.(%{age: 16, vip: false})

p_and/2

Combines two predicates (pred1 and pred2) using logical AND. Returns a predicate that evaluates to true only if both pred1 and pred2 return true.

Examples

is_adult = fn person -> person.age >= 18 end
has_ticket = fn person -> person.tickets > 0 end
can_enter = p_and(is_adult, has_ticket)

can_enter.(%{age: 20, tickets: 1})

can_enter.(%{age: 16, tickets: 1})

p_or/2

Combines two predicates (pred1 and pred2) using logical OR. Returns a predicate that evaluates to true if either pred1 or pred2 return true.

Examples

is_vip = fn person -> person.vip end
is_sponsor = fn person -> person.sponsor end
can_access_vip_area = p_or(is_vip, is_sponsor)

can_access_vip_area.(%{vip: true, sponsor: false})

can_access_vip_area.(%{vip: false, sponsor: false})

p_not/1

Negates a predicate (pred). Returns a predicate that evaluates to true when pred returns false, and vice versa.

Examples

is_minor = fn person -> person.age < 18 end
is_adult = p_not(is_minor)

is_adult.(%{age: 20})

is_adult.(%{age: 16})

p_all/1

Combines a list of predicates (p_list) using logical AND. Returns true only if all predicates return true. An empty list returns true.

Examples

is_adult = fn person -> person.age >= 18 end
has_ticket = fn person -> person.tickets > 0 end
can_enter = p_all([is_adult, has_ticket])

can_enter.(%{age: 20, tickets: 1})

can_enter.(%{age: 16, tickets: 1})

p_any/1

Combines a list of predicates (p_list) using logical OR. Returns true if at least one predicate returns true. An empty list returns false.

Examples

is_vip = fn person -> person.vip end
is_sponsor = fn person -> person.sponsor end
can_access_vip_area = p_any([is_vip, is_sponsor])

can_access_vip_area.(%{vip: true, sponsor: false})

can_access_vip_area.(%{vip: false, sponsor: false})

p_none/1

Combines a list of predicates (p_list) using logical NOR (negated OR). Returns true only if none of the predicates return true. An empty list returns true.

Examples

is_adult = fn person -> person.age >= 18 end
is_vip = fn person -> person.vip end
cannot_enter = p_none([is_adult, is_vip])

cannot_enter.(%{age: 20, vip: true})

cannot_enter.(%{age: 16, vip: false})