reidev275

//greater than or equal
export const gte = <A, K extends keyof A>(field: K, val: A[K]): Filter<A> =>
  or(greater(field, val), equals(field, val));

//less than or equal
export const lte = <A, K extends keyof A>(field: K, val: A[K]): Filter<A> =>
  or(less(field, val), equals(field, val));

//combine 1 to many filters returning true if all are true (and)
export const all = <A>(...dsl: Filter<A>[]): Filter<A> =>

reidev275

export const equals = <A, K extends keyof A>(field: K, val: A[K]): Filter<A> => ({
  kind: "Equals",
  field,
  val
});
export const greater = <A, K extends keyof A>(field: K, val: A[K]): Filter<A> => ({
  kind: "Greater",
  field,
  val
});

reidev275

const query: Filter<JobPosting> = and(
  equals("manager", "Bob Slydell"),
  greater("salary", 50000)
);
  
console.log(
  interpretToSql(query)
)  
 
// ([manager] = 'Bob Slydell' and [salary] > '50000')

reidev275

{
  kind: 'And',
  a: { kind: 'Equals', field: 'manager', val: 'Bob Slydell' },
  b: { kind: 'Greater', field: 'salary', val: 50000 }
}

reidev275

type JobPosting {
  manager: string;
  salary: number;
}

const filter: Filter<JobPosting> = 
  and(
    equals("manager", "Bob Slydell"),
    greater("salary", 50000)
  )

reidev275

export type Filter<A> =
  | { kind: "Equals"; field: keyof A; val: A[keyof A] }
  | { kind: "Greater"; field: keyof A; val: A[keyof A] }
  | { kind: "Less"; field: keyof A; val: A[keyof A] }
  | { kind: "And"; a: Filter<A>; b: Filter<A> }
  | { kind: "Or"; a: Filter<A>; b: Filter<A> };

reidev275

type Monoid<A> = { empty: A; append: (x: A, y: A) => A };

const sum: Monoid<number> = { empty: 0, append: (x, y) => x + y };

interface OrderType {
  period: "ytd" | "mtd";
  orders: number;
}
const data: OrderType[] = [
  { period: "ytd", orders: 3 },

reidev275

import { Filter } from "./filterDsl"

// a sample data model
interface JobPosting {
  manager: string;
  position: string;
}

//a filter of the data model
const query: Filter<JobPosting> = and(

reidev275

module Main where

import Prelude
import Effect (Effect)
import Effect.Console (log)

data Heading = North | South | East | West

data Position = Position 
  { x ∷ Int

reidev275

export type Heading = "north" | "south" | "east" | "west";
export type Position = { heading: Heading; x: number; y: number };

//recursive data structure with our core commands and type
export type DslC =
  | { kind: "position"; a: Position }
  | { kind: "forward"; a: DslC }
  | { kind: "right"; a: DslC };

export const pos = (a: Position): DslC => ({