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Tony Garnock-Jones 2016-07-11 12:16:22 -04:00
parent cca195d597
commit 0314f6a400
1 changed files with 65 additions and 32 deletions
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97
js/examples/two-buyer-protocol/index.js
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@ -6,13 +6,15 @@
var Syndicate = require('../../src/main.js');
/// -->
/// # {{ page.title }}
///
/// This is an extended two-buyer book-purchase protocol, based
/// loosely on an example given in:
///
/// > K. Honda, N. Yoshida, and M. Carbone, “Multiparty asynchronous
/// > session types,” POPL 2008.
/// # The Scenario
/// ## The Scenario
///
/// A book-seller responds to requests for book prices when asked. A
/// pair of prospective buyers run through a shopping list. For each
@ -22,9 +24,9 @@ var Syndicate = require('../../src/main.js');
/// different split. If the second buyer agrees to a split, it then
/// negotiates the purchase of the book with the book-seller.
/// # The Protocol
/// ## The Protocol
/// ## Role: SELLER
/// ### Role: SELLER
///
/// - when interest in `bookQuote($title, _)` appears,
/// asserts `bookQuote(title, Maybe Float)`, `false` meaning not available,
@ -33,17 +35,17 @@ var Syndicate = require('../../src/main.js');
/// asserts `order(title, offer-price, false, false)` for "no sale", otherwise
/// `order(title, offer-price, PositiveInteger, String)`, an accepted sale.
/// ## Role: BUYER
/// ### Role: BUYER
///
/// - observes `bookQuote(title, $price)` to learn prices.
/// - observes `order(title, offer-price, $id, $delivery-date)` to make orders.
/// ## Role: SPLIT-PROPOSER
/// ### Role: SPLIT-PROPOSER
///
/// - observes `splitProposal(title, asking-price, contribution, $accepted)`
/// to make a split-proposal and learn whether it was accepted or not.
/// ## Role: SPLIT-DISPOSER
/// ### Role: SPLIT-DISPOSER
///
/// - when interest in `splitProposal($title, $asking-price, $contribution, _)`
/// appears, asserts `splitProposal(title, askingPrice, contribution, true)`
@ -52,7 +54,7 @@ var Syndicate = require('../../src/main.js');
/// `splitProposal(title, asking-price, contribution, false)` to indicate they
/// are unwilling to go through with the deal.
/// # A Sample Run
/// ## A Sample Run
///
/// Run the program with `../../bin/syndicatec index.js | node` from a
/// checkout of the Syndicate repository.
@ -94,9 +96,9 @@ var Syndicate = require('../../src/main.js');
/// A has bought everything they wanted!
/// The order for The Wind in the Willows has id 10001485, and will be delivered on March 9th
/// # The Code
/// ## The Code
/// ## Type Declarations
/// ### Type Declarations
/// First, we declare *assertion types* for our protocol.
@ -105,7 +107,7 @@ assertion type order(title, price, id, deliveryDate);
assertion type splitProposal(title, price, contribution, accepted);
/// ## Utilities
/// ### Utilities
/// This routine is under consideration for possible addition to the
/// core library.
@ -118,7 +120,7 @@ function whileRelevantAssert(P) {
}
}
/// ## Implementation: SELLER
/// ### Implementation: SELLER
function seller() {
actor {
@ -134,26 +136,36 @@ function seller() {
};
this.nextOrderId = 10001483;
/// Looking up a price yields `false` if no such book is in our
/// inventory.
this.priceOf = function (title) {
return (title in this.books) && this.books[title];
};
/// The seller responds to interest in bookQuotes by asserting a
/// responsive record, if one exists.
react {
during Syndicate.observe(bookQuote($title, _)) {
assert bookQuote(title, title in this.books ? this.books[title] : false);
assert bookQuote(title, this.priceOf(title));
}
}
/// It also responds to order requests.
react {
on asserted Syndicate.observe(order($title, $offerPrice, _, _)) {
on asserted
Syndicate.observe(order($title, $offerPrice, _, _))
{
/// We cannot sell a book we do not have, and we will not sell for
/// less than our asking price.
var askingPrice = title in this.books ? this.books[title] : false;
var askingPrice = this.priceOf(title);
if ((askingPrice === false) || (offerPrice < askingPrice)) {
whileRelevantAssert(order(title, offerPrice, false, false));
whileRelevantAssert(
order(title, offerPrice, false, false));
} else {
/// But if we can sell it, we do so by allocating an order ID and
@ -163,7 +175,8 @@ function seller() {
delete this.books[title];
actor {
whileRelevantAssert(order(title, offerPrice, orderId, "March 9th"));
whileRelevantAssert(
order(title, offerPrice, orderId, "March 9th"));
}
}
}
@ -171,7 +184,7 @@ function seller() {
}
}
/// ## Implementation: SPLIT-PROPOSER and book-quote-requestor
/// ### Implementation: SPLIT-PROPOSER and book-quote-requestor
function buyerA() {
actor {
@ -207,7 +220,8 @@ function buyerA() {
console.log("A learns that "+title+" is out-of-stock.");
buyBooks();
} else {
console.log("A learns that the price of "+title+" is "+price);
console.log("A learns that the price of "+title+
" is "+price);
/// Next, repeatedly make split offers to a SPLIT-DISPOSER until
/// either one is accepted, or the contribution from the
@ -237,14 +251,22 @@ function buyerA() {
/// Make our proposal, and wait for a response.
react until {
case asserted splitProposal(title, price, contribution, true) {
console.log("A learns that the split-proposal for "+title+" was accepted");
case asserted
splitProposal(title, price, contribution, true)
{
console.log("A learns that the split-proposal for "+
title+" was accepted");
buyBooks();
}
case asserted splitProposal(title, price, contribution, false) {
console.log("A learns that the split-proposal for "+title+" was rejected");
trySplit(title, price, contribution + ((price - contribution) / 2));
case asserted
splitProposal(title, price, contribution, false)
{
console.log("A learns that the split-proposal for "+
title+" was rejected");
trySplit(title,
price,
contribution + ((price - contribution) / 2));
}
}
}
@ -252,7 +274,7 @@ function buyerA() {
}
}
/// ## Implementation: SPLIT-DISPOSER and BUYER
/// ### Implementation: SPLIT-DISPOSER and BUYER
function buyerB() {
actor {
@ -266,16 +288,23 @@ function buyerB() {
/// `splitProposal`.
react {
on asserted Syndicate.observe(splitProposal($title, $price, $theirContribution, _)) {
on asserted
Syndicate.observe(splitProposal($title,
$price,
$theirContribution,
_))
{
var myContribution = price - theirContribution;
console.log("B is being asked to contribute "+myContribution+" toward "+title+
" at price "+price);
console.log("B is being asked to contribute "+myContribution+
" toward "+title+" at price "+price);
/// We may not be able to afford contributing this much.
if (myContribution > this.funds) {
console.log("B hasn't enough funds ("+this.funds+" remaining)");
whileRelevantAssert(splitProposal(title, price, theirContribution, false));
console.log("B hasn't enough funds ("+this.funds+
" remaining)");
whileRelevantAssert(
splitProposal(title, price, theirContribution, false));
} else {
/// But if we *can* afford it, update our remaining funds and spawn a
@ -283,7 +312,8 @@ function buyerB() {
/// on a split.
var remainingFunds = this.funds - myContribution;
console.log("B accepts the offer, leaving them with "+remainingFunds+" remaining funds");
console.log("B accepts the offer, leaving them with "+
remainingFunds+" remaining funds");
this.funds = remainingFunds;
actor {
@ -292,7 +322,10 @@ function buyerB() {
/// While waiting for order confirmation, take the opportunity to
/// signal to our SPLIT-PROPOSER that we accepted their proposal.
assert splitProposal(title, price, theirContribution, true);
assert splitProposal(title,
price,
theirContribution,
true);
/// When order confirmation arrives, this purchase is completed.
@ -309,7 +342,7 @@ function buyerB() {
}
}
/// ## Starting Configuration
/// ### Starting Configuration
ground dataspace {
seller();