add Prism.fromPredicate fix #4 (#5)

fix Optional.fromProp

examples/Optional.ts

@@ -26,4 +26,4 @@ const surname = Optional.fromProp<Person, 'surname'>('surname')
 const p: Person = { name: 'Giulio', surname: none }
 
 console.log(surname.getOption(p))
-console.log(surname.set(some('Canti'), p))
+console.log(surname.set('Canti', p))

package.json

@@ -1,6 +1,6 @@
 {
   "name": "monocle-ts",
-  "version": "0.1.0",
+  "version": "0.1.1",
   "description": "A porting of scala monocle library to TypeScript",
   "files": [
     "lib",
@@ -10,7 +10,8 @@
   "jsnext:main": "lib-jsnext/index.js",
   "typings": "lib/index.d.ts",
   "scripts": {
-    "test": "mocha -r ts-node/register test/*.ts",
+    "mocha": "mocha -r ts-node/register test/*.ts",
+    "test": "npm run mocha",
     "clean": "rm -rf lib/* && rm -rf lib-jsnext/*",
     "build": "npm run clean && tsc && tsc -m es6 --outDir lib-jsnext"
   },
@@ -25,7 +26,7 @@
   },
   "homepage": "https://github.com/gcanti/monocle-ts",
   "dependencies": {
-    "fp-ts": "^0.2.0"
+    "fp-ts": "^0.2.1"
   },
   "devDependencies": {
     "@types/mocha": "^2.2.38",

src/index.ts

@@ -4,7 +4,7 @@ import { StaticApplicative } from 'fp-ts/lib/Applicative'
 import { StaticFoldable, foldMap } from 'fp-ts/lib/Foldable'
 import { StaticTraversable } from 'fp-ts/lib/Traversable'
 import * as option from 'fp-ts/lib/Option'
-import { Some, Option } from 'fp-ts/lib/Option'
+import { Option, none, some } from 'fp-ts/lib/Option'
 import { identity, constant, Predicate } from 'fp-ts/lib/function'
 import * as id from 'fp-ts/lib/Identity'
 import * as con from 'fp-ts/lib/Const'
@@ -43,7 +43,7 @@ export class Iso<S, A> {
   /** view a ISO as a Prism */
   asPrism(): Prism<S, A> {
     return new Prism(
-      s => new Some(this.get(s)),
+      s => some(this.get(s)),
       this.reverseGet
     )
   }
@@ -101,7 +101,7 @@ export class Lens<S, A> {
   /** view a Lens as a Option */
   asOptional(): Optional<S, A> {
     return new Optional(
-      s => new Some(this.get(s)),
+      s => some(this.get(s)),
       this.set
     )
   }
@@ -118,6 +118,13 @@ export class Prism<S, A> {
     public reverseGet: (a: A) => S
   ) { }
 
+  static fromPredicate<A>(predicate: Predicate<A>): Prism<A, A> {
+    return new Prism<A, A>(
+      s => predicate(s) ? some(s) : none,
+      a => a
+    )
+  }
+
   modify(f: (a: A) => A, s: S): S {
     return this.modifyOption(f, s)
       .fold(constant(s), identity)
@@ -157,11 +164,11 @@ export class Optional<S, A> {
     public set: (a: A, s: S) => S
   ){}
 
-  /** generate an optional from a type and a prop */
-  static fromProp<T extends { [K in P]: Option<any> }, P extends keyof T>(prop: P): Optional<T, T[P]> {
+  /** generate an optional from a type and a prop which is a `Option` */
+  static fromProp<T extends { [K in P]: Option<any> }, P extends keyof T>(prop: P): Optional<T, T[P]['_A']> {
     return new Optional<T, T[P]>(
       s => s[prop],
-      (a, s) => Object.assign({}, s, { [prop as any]: a })
+      (a, s) => Object.assign({}, s, { [prop as any]: some(a) })
     )
   }
 

test/Optional.ts

@@ -12,11 +12,11 @@ describe('Optional', () => {
 
   it('getOption', () => {
     eq(optional.getOption({ a: none }), none)
+    eq(optional.getOption({ a: some(1) }), some(1))
   })
 
   it('set', () => {
-    eq(optional.set(none, { a: some(1) }).a, none)
-    eq(optional.set(some(2), { a: some(1) }).a, some(2))
+    eq(optional.set(2, { a: some(1) }).a, some(2))
   })
 
 })

test/Prism.ts

@@ -0,0 +1,13 @@
+import { none, some } from 'fp-ts/lib/Option'
+import { Prism } from '../src'
+import { eqOptions as eq } from './helpers'
+
+describe('Prism', () => {
+
+  it('fromPredicate', () => {
+    const prism = Prism.fromPredicate<number>(n => n % 1 === 0)
+    eq(prism.getOption(1), some(1))
+    eq(prism.getOption(1.1), none)
+  })
+
+})