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Add mask combinator #52

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Apr 10, 2018
Merged

Add mask combinator #52

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73c7420
Add mask combinator
tardieu Apr 9, 2018
9e66c5e
Add composer.mask tests
tardieu Apr 10, 2018
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34 changes: 30 additions & 4 deletions composer.js
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Original file line number Diff line number Diff line change
Expand Up @@ -283,7 +283,7 @@ class Composer {

repeat(count) { // varargs, no options
if (typeof count !== 'number') throw new ComposerError('Invalid argument', count)
return this.let({ count }, this.while(this.function(() => count-- > 0, { helper: 'repeat_1' }), this.seq(...Array.prototype.slice.call(arguments, 1))))
return this.let({ count }, this.while(this.function(() => count-- > 0, { helper: 'repeat_1' }), this.mask(this.seq(...Array.prototype.slice.call(arguments, 1)))))
}

retry(count) { // varargs, no options
Expand All @@ -292,10 +292,15 @@ class Composer {
return this.let({ count },
this.function(params => ({ params }), { helper: 'retry_1' }),
this.dowhile(
this.finally(this.function(({ params }) => params, { helper: 'retry_2' }), attempt),
this.finally(this.function(({ params }) => params, { helper: 'retry_2' }), this.mask(attempt)),
this.function(({ result }) => typeof result.error !== 'undefined' && count-- > 0, { helper: 'retry_3' })),
this.function(({ result }) => result, { helper: 'retry_4' }))
}

mask(body, options) {
if (arguments.length > 2) throw new ComposerError('Too many arguments')
return new Composition({ type: 'mask', body: this.task(body) }, options)
}
}

module.exports = new Composer()
Expand Down Expand Up @@ -333,6 +338,9 @@ function init(__eval__, composition) {
case 'let':
var body = compile(json.body, path + '.body')
return [[{ type: 'let', let: json.declarations, path }], body, [{ type: 'exit', path }]].reduce(chain)
case 'mask':
var body = compile(json.body, path + '.body')
return [[{ type: 'mask', path }], body, [{ type: 'exit', path }]].reduce(chain)
case 'retain':
var body = compile(json.body, path + '.body')
var fsm = [[{ type: 'push', path }], body, [{ type: 'pop', collect: true, path }]].reduce(chain)
Expand Down Expand Up @@ -433,14 +441,29 @@ function init(__eval__, composition) {

// run function f on current stack
function run(f) {
// handle let/mask pairs
const view = []
let n = 0
for (let i in stack) {
if (typeof stack[i].mask !== 'undefined') {
n++
} else if (typeof stack[i].let !== 'undefined') {
if (n === 0) {
view.push(stack[i])
} else {
n--
}
}
}

// update value of topmost matching symbol on stack if any
function set(symbol, value) {
const element = stack.find(element => typeof element.let !== 'undefined' && typeof element.let[symbol] !== 'undefined')
const element = view.find(element => typeof element.let !== 'undefined' && typeof element.let[symbol] !== 'undefined')
if (typeof element !== 'undefined') element.let[symbol] = JSON.parse(JSON.stringify(value))
}

// collapse stack for invocation
const env = stack.reduceRight((acc, cur) => typeof cur.let === 'object' ? Object.assign(acc, cur.let) : acc, {})
const env = view.reduceRight((acc, cur) => typeof cur.let === 'object' ? Object.assign(acc, cur.let) : acc, {})
let main = '(function(){try{'
for (const name in env) main += `var ${name}=arguments[1]['${name}'];`
main += `return eval((${f}))(arguments[0])}finally{`
Expand Down Expand Up @@ -476,6 +499,9 @@ function init(__eval__, composition) {
case 'let':
stack.unshift({ let: JSON.parse(JSON.stringify(json.let)) })
break
case 'mask':
stack.unshift({ mask: true })
break
case 'exit':
if (stack.length === 0) return internalError(`State ${current} attempted to pop from an empty stack`)
stack.shift()
Expand Down
36 changes: 36 additions & 0 deletions test/test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -517,6 +517,42 @@ describe('composer', function () {
})
})

describe('mask', function () {
it('let/let/mask', function () {
return invoke(composer.let({ x: 42 }, composer.let({ x: 69 }, composer.mask(() => x))))
.then(activation => assert.deepEqual(activation.response.result, { value: 42 }))
})

it('let/mask/let', function () {
return invoke(composer.let({ x: 42 }, composer.mask(composer.let({ x: 69 }, () => x))))
.then(activation => assert.deepEqual(activation.response.result, { value: 69 }))
})

it('let/let/try/mask', function () {
return invoke(composer.let({ x: 42 }, composer.let({ x: 69 },
composer.try(composer.mask(() => x)), () => { })))
.then(activation => assert.deepEqual(activation.response.result, { value: 42 }))
})

it('let/let/let/mask', function () {
return invoke(composer.let({ x: 42 }, composer.let({ x: 69 },
composer.let({ x: -1 }, composer.mask(() => x)))))
.then(activation => assert.deepEqual(activation.response.result, { value: 69 }))
})

it('let/let/let/mask/mask', function () {
return invoke(composer.let({ x: 42 }, composer.let({ x: 69 },
composer.let({ x: -1 }, composer.mask(composer.mask(() => x))))))
.then(activation => assert.deepEqual(activation.response.result, { value: 42 }))
})

it('let/let/mask/let/mask', function () {
return invoke(composer.let({ x: 42 }, composer.let({ x: 69 },
composer.mask(composer.let({ x: -1 }, composer.mask(() => x))))))
.then(activation => assert.deepEqual(activation.response.result, { value: 42 }))
})
})

describe('retain', function () {
it('base case', function () {
return invoke(composer.retain('TripleAndIncrement'), { n: 3 })
Expand Down