Effect Domain Predicates

Domain Predicates Skill

Generate complete sets of predicates and Order instances for domain types, derived from typeclass implementations.

Effect Source Reference

The Effect v4 source is available at ~/.local/share/opencode/repos/github.com/Effect-TS/effect@main/. Browse and read files there directly to look up APIs, types, and implementations.

Reference this for:

• Full Schema API: packages/effect/SCHEMA.md
• Order source: packages/effect/src/Order.ts
• Equivalence source: packages/effect/src/Equivalence.ts
• Predicate source: packages/effect/src/Predicate.ts
• Effect source: packages/effect/src/

Pattern: Deep Structural Equality (v4)

In v4, Equal.equals performs deep structural comparison by default — no special wrapping is needed:

import { Schema, Equal, DateTime } from 'effect';

export const Task = Schema.TaggedStruct('pending', {
	id: Schema.String,
	createdAt: Schema.DateTimeUtc
});

export type Task = Schema.Schema.Type<typeof Task>;

declare const makeTask: (props: {
	id: string;
	createdAt: DateTime.Utc;
}) => Task;
declare const now: DateTime.Utc;

// Usage: Deep structural equality (automatic in v4)
const task1 = makeTask({ id: '123', createdAt: now });
const task2 = makeTask({ id: '123', createdAt: now });

Equal.equals(task1, task2); // true - deep structural equality

Pattern: Equivalence from Schema

When you need an Equivalence instance (for use with combinators), derive it from the schema:

import { Schema, Array } from 'effect';
import * as Equivalence from 'effect/Equivalence';

class Task extends Schema.Class<Task>('Task')({ id: Schema.String }) {}

// Derive from schema (structural equality)
export const TaskEquivalence = Schema.toEquivalence(Task);

declare const tasks: Array<Task>;

// Usage with combinators
const uniqueTasks = Array.dedupeWith(tasks, TaskEquivalence);

Pattern: Field-Based Equivalence with Equivalence.mapInput

Compare by specific fields using Equivalence.mapInput:

import { DateTime } from 'effect';
import * as Equivalence from 'effect/Equivalence';

interface Task {
	readonly _tag: string;
	readonly id: string;
	readonly createdAt: DateTime.Utc;
}

/**
 * Compare tasks by ID only.
 *
 * @category Equivalence
 * @since 0.1.0
 * @example
 * import * as Task from "@/schemas/Task"
 * import * as Array from "effect/Array"
 *
 * const uniqueById = Array.dedupeWith(tasks, Task.EquivalenceById)
 */
export const EquivalenceById = Equivalence.mapInput(
	Equivalence.String,
	(task: Task) => task.id
);

/**
 * Compare by status tag.
 *
 * @category Equivalence
 * @since 0.1.0
 */
export const EquivalenceByTag = Equivalence.mapInput(
	Equivalence.String,
	(task: Task) => task._tag
);

/**
 * Compare by creation date.
 *
 * @category Equivalence
 * @since 0.1.0
 */
export const EquivalenceByCreatedAt = Equivalence.mapInput(
	DateTime.Equivalence,
	(task: Task) => task.createdAt
);

Key Pattern: Equivalence.mapInput

• Signature: Equivalence.mapInput(baseEquivalence, (value) => extractField)
• Compose from simpler equivalences
• Map domain type to comparable value
• Dual API: data-first and data-last

Pattern: Combining Equivalences

Use Equivalence.combine for two-field equality and Equivalence.combineAll for three or more fields:

import { DateTime } from 'effect';
import * as Equivalence from 'effect/Equivalence';

interface Task {
	readonly _tag: string;
	readonly id: string;
	readonly createdAt: DateTime.Utc;
}

declare const EquivalenceByTag: Equivalence.Equivalence<Task>;
declare const EquivalenceById: Equivalence.Equivalence<Task>;
declare const EquivalenceByCreatedAt: Equivalence.Equivalence<Task>;

/**
 * Compare by tag first, then by ID.
 *
 * Both must match for equivalence.
 *
 * @category Equivalence
 * @since 0.1.0
 * @example
 * import * as Task from "@/schemas/Task"
 *
 * const areSame = Task.EquivalenceByTagAndId(task1, task2)
 */
export const EquivalenceByTagAndId = Equivalence.combine(
	EquivalenceByTag,
	EquivalenceById
);

/**
 * Compare by multiple criteria for exact equality.
 *
 * @category Equivalence
 * @since 0.1.0
 */
export const EquivalenceComplete = Equivalence.combineAll([
	EquivalenceByTag,
	EquivalenceById,
	EquivalenceByCreatedAt
]);

Key Pattern: Equivalence.combine / combineAll

• Equivalence.combine combines two equivalences
• Use Equivalence.combineAll([...]) for three or more equivalences
• All must match for equivalence (AND logic)
• Order doesn't matter (unlike Order.combine)

Pattern: Typeclass-Derived Predicates

When a domain type implements a typeclass, re-export all relevant predicates:

import { DateTime, Duration, Schema } from 'effect';
import * as Order from 'effect/Order';

// Inline typeclass interface declarations (instead of module augmentations)
interface SchedulableInstance<A> {
	readonly get: (self: A) => DateTime.DateTime;
	readonly set: (self: A, date: DateTime.DateTime) => A;
}

interface DurableInstance<A> {
	readonly get: (self: A) => Duration.Duration;
	readonly set: (self: A, duration: Duration.Duration) => A;
}

// Typeclass module declarations
declare const Schedulable$: {
	make: <A>(
		get: (self: A) => DateTime.DateTime,
		set: (self: A, date: DateTime.DateTime) => A
	) => SchedulableInstance<A>;
	isScheduledBefore: <A>(
		instance: SchedulableInstance<A>
	) => (date: DateTime.DateTime) => (self: A) => boolean;
	isScheduledAfter: <A>(
		instance: SchedulableInstance<A>
	) => (date: DateTime.DateTime) => (self: A) => boolean;
	isScheduledBetween: <A>(
		instance: SchedulableInstance<A>
	) => (
		start: DateTime.DateTime,
		end: DateTime.DateTime
	) => (self: A) => boolean;
	isScheduledOn: <A>(
		instance: SchedulableInstance<A>
	) => (date: DateTime.DateTime) => (self: A) => boolean;
	isScheduledToday: <A>(
		instance: SchedulableInstance<A>
	) => (self: A) => boolean;
	isScheduledThisWeek: <A>(
		instance: SchedulableInstance<A>
	) => (self: A) => boolean;
	isScheduledThisMonth: <A>(
		instance: SchedulableInstance<A>
	) => (self: A) => boolean;
};

declare const Durable$: {
	make: <A>(
		get: (self: A) => Duration.Duration,
		set: (self: A, duration: Duration.Duration) => A
	) => DurableInstance<A>;
	isMoreThan: <A>(
		instance: DurableInstance<A>
	) => (min: Duration.Duration) => (self: A) => boolean;
	isLessThan: <A>(
		instance: DurableInstance<A>
	) => (max: Duration.Duration) => (self: A) => boolean;
	isBetween: <A>(
		instance: DurableInstance<A>
	) => (
		min: Duration.Duration,
		max: Duration.Duration
	) => (self: A) => boolean;
	hasExactDuration: <A>(
		instance: DurableInstance<A>
	) => (duration: Duration.Duration) => (self: A) => boolean;
};

interface Appointment {
	readonly date: DateTime.Utc;
	readonly duration: Duration.Duration;
}

declare const Appointment: {
	make: (props: Partial<Appointment>) => Appointment;
};

// Create typeclass instances
export const Schedulable = Schedulable$.make<Appointment>(
	(self: Appointment) => self.date,
	(self: Appointment, date: DateTime.DateTime) =>
		Appointment.make({ ...self, date: DateTime.toUtc(date) })
);

export const Durable = Durable$.make<Appointment>(
	(self: Appointment) => self.duration,
	(self: Appointment, duration: Duration.Duration) =>
		Appointment.make({ ...self, duration })
);

// Re-export all Schedulable predicates
export const isScheduledBefore = Schedulable$.isScheduledBefore(Schedulable);
export const isScheduledAfter = Schedulable$.isScheduledAfter(Schedulable);
export const isScheduledBetween = Schedulable$.isScheduledBetween(Schedulable);
export const isScheduledOn = Schedulable$.isScheduledOn(Schedulable);
export const isScheduledToday = Schedulable$.isScheduledToday(Schedulable);
export const isScheduledThisWeek =
	Schedulable$.isScheduledThisWeek(Schedulable);
export const isScheduledThisMonth =
	Schedulable$.isScheduledThisMonth(Schedulable);

// Re-export all Durable predicates
export const hasMinimumDuration = Durable$.isMoreThan(Durable);
export const hasMaximumDuration = Durable$.isLessThan(Durable);
export const hasDurationBetween = Durable$.isBetween(Durable);
export const hasExactDuration = Durable$.hasExactDuration(Durable);

Pattern: Order Instances with Order.mapInput

Compose orders from simpler base orders using Order.mapInput:

import { DateTime } from 'effect';
import * as Order from 'effect/Order';
import * as String from 'effect/String';

interface Task {
	readonly _tag: 'pending' | 'active' | 'completed';
	readonly id: string;
	readonly createdAt: DateTime.Utc;
}

/**
 * Order by ID using Order.mapInput.
 *
 * @category Orders
 * @since 0.1.0
 * @example
 * import * as Task from "@/schemas/Task"
 * import * as Array from "effect/Array"
 *
 * const sorted = Array.sort(tasks, Task.OrderById)
 */
export const OrderById: Order.Order<Task> = Order.mapInput(
	Order.String,
	(task: Task) => task.id
);

/**
 * Order by creation date.
 *
 * @category Orders
 * @since 0.1.0
 */
export const OrderByCreatedAt: Order.Order<Task> = Order.mapInput(
	DateTime.Order,
	(task: Task) => task.createdAt
);

/**
 * Order by status tag.
 *
 * @category Orders
 * @since 0.1.0
 */
export const OrderByTag: Order.Order<Task> = Order.mapInput(
	Order.String,
	(task: Task) => task._tag
);

/**
 * Order by priority (domain-specific logic).
 *
 * @category Orders
 * @since 0.1.0
 */
export const OrderByPriority: Order.Order<Task> = Order.mapInput(
	Order.Number,
	(task: Task) => {
		const priorities = { pending: 0, active: 1, completed: 2 };
		return priorities[task._tag];
	}
);

Key Pattern: Order.mapInput

• Signature: Order.mapInput(baseOrder, (value) => extractField)
• Compose from existing orders (Order.String, Order.Number, DateTime.Order, etc.)
• Map domain type to comparable value
• Dual API: data-first and data-last

Pattern: Combining Orders with Order.combine

Use Order.combine for multi-criteria sorting:

import { DateTime } from 'effect';
import * as Order from 'effect/Order';

interface Task {
	readonly _tag: 'pending' | 'active' | 'completed';
	readonly id: string;
	readonly createdAt: DateTime.Utc;
}

declare const OrderByPriority: Order.Order<Task>;
declare const OrderByCreatedAt: Order.Order<Task>;
declare const OrderByTag: Order.Order<Task>;
declare const OrderById: Order.Order<Task>;

/**
 * Sort by priority first, then by creation date.
 *
 * @category Orders
 * @since 0.1.0
 * @example
 * import * as Task from "@/schemas/Task"
 * import * as Array from "effect/Array"
 *
 * // High priority tasks first, then by oldest
 * const sorted = Array.sort(tasks, Task.OrderByPriorityThenDate)
 */
export const OrderByPriorityThenDate: Order.Order<Task> = Order.combine(
	OrderByPriority,
	OrderByCreatedAt
);

/**
 * Sort by tag, then ID, then creation date.
 *
 * @category Orders
 * @since 0.1.0
 */
export const OrderComplex: Order.Order<Task> = Order.combineAll([
	OrderByTag,
	OrderById,
	OrderByCreatedAt
]);

Key Pattern: Order.combine / combineAll

• Order.combine combines two orders for multi-criteria sorting
• Use Order.combineAll([...]) for three or more orders
• First order takes precedence, then second, etc.
• Order matters (unlike Equivalence.combine)
• Returns combined order that can be used with Array.sort

Pattern: Comprehensive Order Instances

Provide extensive sorting capabilities:

import { DateTime, Duration } from 'effect';
import * as Order from 'effect/Order';
import * as String from 'effect/String';

// Inline typeclass interface declarations
interface SchedulableInstance<A> {
	readonly get: (self: A) => DateTime.DateTime;
	readonly set: (self: A, date: DateTime.DateTime) => A;
}

interface DurableInstance<A> {
	readonly get: (self: A) => Duration.Duration;
	readonly set: (self: A, duration: Duration.Duration) => A;
}

// Typeclass module declarations
declare const Schedulable$: {
	OrderByScheduledTime: <A>(
		instance: SchedulableInstance<A>
	) => Order.Order<A>;
	OrderByDayOfWeek: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByTimeOfDay: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByHour: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByMonth: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByYear: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByYearMonth: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByDateOnly: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByDayPeriod: <A>(instance: SchedulableInstance<A>) => Order.Order<A>;
	OrderByBusinessHours: <A>(
		instance: SchedulableInstance<A>
	) => Order.Order<A>;
	OrderByWeekdayFirst: <A>(
		instance: SchedulableInstance<A>
	) => Order.Order<A>;
};

declare const Durable$: {
	OrderByDuration: <A>(instance: DurableInstance<A>) => Order.Order<A>;
	OrderByHours: <A>(instance: DurableInstance<A>) => Order.Order<A>;
	OrderByMinutes: <A>(instance: DurableInstance<A>) => Order.Order<A>;
	OrderBySeconds: <A>(instance: DurableInstance<A>) => Order.Order<A>;
};

type AppointmentStatus = 'scheduled' | 'confirmed' | 'completed' | 'cancelled';

interface Appointment {
	readonly date: DateTime.Utc;
	readonly duration: Duration.Duration;
	readonly status: AppointmentStatus;
}

declare const Schedulable: SchedulableInstance<Appointment>;
declare const Durable: DurableInstance<Appointment>;

// Schedulable orders (temporal sorting)
export const OrderByScheduledTime =
	Schedulable$.OrderByScheduledTime(Schedulable);
export const OrderByDayOfWeek = Schedulable$.OrderByDayOfWeek(Schedulable);
export const OrderByTimeOfDay = Schedulable$.OrderByTimeOfDay(Schedulable);
export const OrderByHour = Schedulable$.OrderByHour(Schedulable);
export const OrderByMonth = Schedulable$.OrderByMonth(Schedulable);
export const OrderByYear = Schedulable$.OrderByYear(Schedulable);
export const OrderByYearMonth = Schedulable$.OrderByYearMonth(Schedulable);
export const OrderByDateOnly = Schedulable$.OrderByDateOnly(Schedulable);
export const OrderByDayPeriod = Schedulable$.OrderByDayPeriod(Schedulable);
export const OrderByBusinessHours =
	Schedulable$.OrderByBusinessHours(Schedulable);
export const OrderByWeekdayFirst =
	Schedulable$.OrderByWeekdayFirst(Schedulable);

// Durable orders (duration sorting)
export const OrderByDuration = Durable$.OrderByDuration(Durable);
export const OrderByHours = Durable$.OrderByHours(Durable);
export const OrderByMinutes = Durable$.OrderByMinutes(Durable);
export const OrderBySeconds = Durable$.OrderBySeconds(Durable);

// Domain-specific orders using Order.mapInput
export const OrderByStatus: Order.Order<Appointment> = Order.mapInput(
	String.Order,
	(appt: Appointment) => appt.status
);

export const OrderByStatusPriority: Order.Order<Appointment> = Order.mapInput(
	Order.Number,
	(appt: Appointment) => {
		const priorities: Record<AppointmentStatus, number> = {
			scheduled: 0,
			confirmed: 1,
			completed: 2,
			cancelled: 3
		};
		return priorities[appt.status];
	}
);

// Combined orders for complex sorting
export const OrderByStatusThenTime: Order.Order<Appointment> = Order.combine(
	OrderByStatusPriority,
	OrderByScheduledTime
);

Usage Examples

Equality Examples

import { Equal, Array } from 'effect';
import * as Equivalence from 'effect/Equivalence';

declare module '@/schemas/Task' {
	export interface Task {
		readonly _tag: string;
		readonly id: string;
	}
	export const EquivalenceById: Equivalence.Equivalence<Task>;
	export const EquivalenceByTagAndId: Equivalence.Equivalence<Task>;
}

import * as Task from '@/schemas/Task';

declare const task1: Task.Task;
declare const task2: Task.Task;
declare const tasks: Array<Task.Task>;
declare const searchTask: Task.Task;

// Deep structural equality (automatic in v4)
const areSame = Equal.equals(task1, task2);

// Deduplicate by ID only
const uniqueById = Array.dedupeWith(tasks, Task.EquivalenceById);

// Deduplicate by tag and ID
const uniqueByTagAndId = Array.dedupeWith(tasks, Task.EquivalenceByTagAndId);

// Find if array contains equivalent task
const hasTask = Array.containsWith(tasks, Task.EquivalenceById)(searchTask);

Filtering Examples

Document how these predicates enable powerful filtering:

import { DateTime, Duration, Array } from 'effect';
import { pipe } from 'effect/Function';

declare module '@/schemas/Appointment' {
	export interface Appointment {
		readonly date: DateTime.Utc;
	}
	export const isScheduledBefore: (
		date: DateTime.DateTime
	) => (appointment: Appointment) => boolean;
}

import * as Appointment from '@/schemas/Appointment';

declare const appointments: Array<Appointment.Appointment>;

/**
 * Filter appointments scheduled before a date.
 *
 * @example
 * import * as Appointment from "@/schemas/Appointment"
 * import * as DateTime from "effect/DateTime"
 * import * as Duration from "effect/Duration"
 * import * as Array from "effect/Array"
 * import { pipe } from "effect/Function"
 *
 * const tomorrow = DateTime.addDuration(
 *   DateTime.makeUnsafe('2026-09-06T00:00:00Z'),
 *   Duration.days(1)
 * )
 *
 * const beforeTomorrow = pipe(
 *   appointments,
 *   Array.filter(Appointment.isScheduledBefore(tomorrow))
 * )
 */
// Deterministic fixture; in runtime code obtain the instant with yield* DateTime.now.
const tomorrow = DateTime.addDuration(DateTime.makeUnsafe('2026-09-06T00:00:00Z'), Duration.days(1));

const beforeTomorrow = pipe(
	appointments,
	Array.filter(Appointment.isScheduledBefore(tomorrow))
);

Sorting Examples

import { Array, DateTime } from 'effect';
import * as Order from 'effect/Order';
import { pipe } from 'effect/Function';

declare module '@/schemas/Task' {
	export interface Task {
		readonly _tag: 'pending' | 'active' | 'completed';
		readonly id: string;
		readonly createdAt: DateTime.Utc;
	}
	export const OrderById: Order.Order<Task>;
	export const OrderByPriority: Order.Order<Task>;
	export const OrderByCreatedAt: Order.Order<Task>;
	export const isPending: (task: Task) => boolean;
}

import * as Task from '@/schemas/Task';

declare const tasks: Array<Task.Task>;

// Simple sort by single field
const sortedById = Array.sort(tasks, Task.OrderById);

// Multi-criteria sort
const sortedComplex = Array.sort(
	tasks,
	Order.combine(Task.OrderByPriority, Task.OrderByCreatedAt)
);

// Sort with filter
const sortedFiltered = pipe(
	tasks,
	Array.filter(Task.isPending),
	Array.sort(Task.OrderByCreatedAt)
);

Pattern: Complex Filtering

Combine predicates for sophisticated queries:

import { DateTime, Duration, Array } from 'effect';
import { pipe } from 'effect/Function';
import * as Order from 'effect/Order';
import * as Equivalence from 'effect/Equivalence';

declare module '@/schemas/Appointment' {
	export interface Appointment {
		readonly id: string;
		readonly date: DateTime.Utc;
		readonly duration: Duration.Duration;
		readonly status: string;
	}
	export const isScheduledThisWeek: (appointment: Appointment) => boolean;
	export const hasMinimumDuration: (
		min: Duration.Duration
	) => (appointment: Appointment) => boolean;
	export const isScheduledToday: (appointment: Appointment) => boolean;
	export const OrderByStatusPriority: Order.Order<Appointment>;
	export const OrderByScheduledTime: Order.Order<Appointment>;
	export const EquivalenceById: Equivalence.Equivalence<Appointment>;
	export const OrderByPriorityThenDate: Order.Order<Appointment>;
}

import * as Appointment from '@/schemas/Appointment';

declare const appointments: Array<Appointment.Appointment>;

// Find long appointments this week
const longThisWeek = pipe(
	appointments,
	Array.filter(Appointment.isScheduledThisWeek),
	Array.filter(Appointment.hasMinimumDuration(Duration.hours(2)))
);

// Sort by multiple criteria
const sorted = pipe(
	appointments,
	Array.filter(Appointment.isScheduledToday),
	Array.sort(
		Order.combine(
			Appointment.OrderByStatusPriority,
			Appointment.OrderByScheduledTime
		)
	)
);

// Deduplicate and sort
const uniqueSorted = pipe(
	appointments,
	Array.dedupeWith(Appointment.EquivalenceById),
	Array.sort(Appointment.OrderByPriorityThenDate)
);

Checklist for Complete Coverage

Equality

• Equal.equals() works via deep structural comparison (automatic in v4)
• Export Schema.toEquivalence() when needed for combinators
• Export field-based equivalences using Equivalence.mapInput
• Export combined equivalences using Equivalence.combine

Orders

• Export orders for all sortable fields using Order.mapInput
• Export combined orders using Order.combine
• Document which field takes precedence in combined orders

Schedulable types

• isScheduledBefore
• isScheduledAfter
• isScheduledBetween
• isScheduledOn
• isScheduledToday
• isScheduledThisWeek
• isScheduledThisMonth
• All Order instances

Durable types

• hasMinimumDuration (isMoreThan)
• hasMaximumDuration (isLessThan)
• hasDurationBetween (isBetween)
• hasExactDuration
• All Order instances

Domain-specific fields

• Predicate for each variant (isPending, isActive, etc.)
• Order by field value using Order.mapInput
• Order by priority/importance if applicable
• Combined orders for common sorting patterns

Documentation Requirements

Every predicate, equivalence, and order MUST have:

• JSDoc description
• @category tag
• @since tag
• @example with realistic usage showing imports and pipe

Key Patterns Summary

1. Deep Structural Equality (v4)

import { Schema, Equal } from 'effect';

const TaskSchema = Schema.TaggedStruct('task', { id: Schema.String });
type Task = Schema.Schema.Type<typeof TaskSchema>;

declare const t1: Task;
declare const t2: Task;

// Usage: Equal.equals(t1, t2) — deep structural comparison is automatic in v4
const areSame = Equal.equals(t1, t2);

2. Schema.toEquivalence() for Combinators

import { Schema, Array } from 'effect';

class Task extends Schema.Class<Task>('Task')({ id: Schema.String }) {}

export const Equivalence = Schema.toEquivalence(Task);

declare const tasks: Array<Task>;

// Usage: Array.dedupeWith(tasks, Equivalence)
const uniqueTasks = Array.dedupeWith(tasks, Equivalence);

3. Equivalence.mapInput for Field-Based

import * as Equivalence from 'effect/Equivalence';

interface Task {
	readonly id: string;
}

const EquivalenceById = Equivalence.mapInput(
	Equivalence.String,
	(t: Task) => t.id
);

4. Equivalence.combine for Multi-Field

import * as Equivalence from 'effect/Equivalence';

interface Task {
	readonly _tag: string;
	readonly id: string;
}

declare const EquivalenceByTag: Equivalence.Equivalence<Task>;
declare const EquivalenceById: Equivalence.Equivalence<Task>;

const EquivalenceCombined = Equivalence.combine(
	EquivalenceByTag,
	EquivalenceById
);

5. Order.mapInput for Field-Based Sorting

import * as Order from 'effect/Order';

interface Task {
	readonly id: string;
}

const OrderById = Order.mapInput(Order.String, (t: Task) => t.id);

6. Order.combine for Multi-Criteria Sorting

import * as Order from 'effect/Order';

interface Task {
	readonly priority: number;
	readonly date: Date;
}

declare const OrderByPriority: Order.Order<Task>;
declare const OrderByDate: Order.Order<Task>;

const OrderCombined = Order.combine(OrderByPriority, OrderByDate);

This ensures comprehensive equality checking, predicates, and sorting capabilities are discoverable and developers understand how to use them effectively with Effect's compositional patterns.