apress / practical-tla-plus

Source Code for 'Practical TLA+' by Hillel Wayne

Apress Source Code

This repository accompanies Practical TLA+ by Hillel Wayne (Apress, 2018).

Download the files as a zip using the green button, or clone the repository to your machine using Git.

Releases

Release v1.0 corresponds to the code in the published book, without corrections or updates.

Contributions

See the file Contributing.md for more information on how you can contribute to this repository.

practical-tla-plus's Issues

Pluscal translation of algorithms

Some algorithms in this repo include Pluscal translation, others (such as recycler.tla) do not. I think it would be useful if all algorithms included translations

Chapter 3 - page 54

The sentence "Functions ... have no restrictions on recursion" implied to me that operations could not be recursive. However, they can be and here is what SumUpTo(n) might look like as a recursive operator:

RECURSIVE SumUpTo(_)
SumUpTo(n) == IF n=0 THEN 0 ELSE n + SumUpTo(n-1) 

Typo

Chapter 2, page 37: «since we'd be using Append instead of Cardinality» should read «since we'd be using Len instead of Cardinality».

Chapter 5 - Concurrency: Typos and Questions

At page 90 where Actors are added to the cache code, in place of WaitForResources it should be UseResources (or if it's correct with WaitForResources, should change the pages before this one).

Great book @hwayne o/ great work

Add a copy of each iteration for each modules

Currently, only some modules are included in this repo. It would be helpful if this repo included each iteration of each module e.g. the version of recycler from the start of chapter 3. Related to issue #10

Add a comment to each algorithm with a book page number

I would be great if you could add a comment to each module specifying exactly which algorithm in the book it corresponds with. E.g. I assumed telephone.2.tla would be the algorithm from page 41 but it is the algorithm from page 42.

Complex Behaviours

Page 34 says "There are three basic ways to do this."

Then we have Multiple Starting States with an example, followed by Nondeterministic Behavior with an example.
The summary then confirms that there are only 2 ways discussed... is there another way that may have been dropped?

Repository does not contain PT library

I am now trying to set up the TLA+ toolbox. However, I cannot find the PT library in this repository while the book says "Download the module from https://github.com/Apress/practical-tla-plus." Could you add the library to the repository?

Chapter 2 - Pluscal, Page 33

Chapter 2 - Pluscal, Page 33.

The new macro code should be bold

Chapter 7: binary search and overflows

The last part of the binary algorithm in chapter 7 suggests to create the NoOverflows invariant. In doing so, the invariant is violated due to high taking MaxInt + 1 value (tested with MaxInt == 7).

The algorithm requires a small fix in the elsif check:

  goto Result;
elsif seq[m] < target /\ m < high then 
   low := m + 1;
else 

This allow the model to pass and terminate without causing further overflows.

Chapter 3 - page 45

The following LAMBDA param1, param2, paramN: body should say LAMBDA param1, param2, ..., paramN: body on page 45