This repo records my learning notes for TLA+.
TLA+ is a programming language to model programs or systems to identify fundamental errors in algorithms or designs. It belongs to the family of model checking, along with other tools like SPIN, (C|J|E)BMC, etc. The active community is a direct reason I chose to learn it recently, especially when Leslie Lamport shared his new TLA+ book draft on January 3rd, 2024. Receiving feedback is crucial for me, or at least very beneficial and necessary, to understand new concepts thoroughly and apply them in daily work.
The notes here have no finalized format and may keep changing, and the content only represents my understanding. If you find any incorrectness, welcome to fill an issue! Very appreciated!
Click to download https://github.com/tlaplus/tlaplus/releases/download/v1.7.1/TLAToolbox-1.7.1-win32.win32.x86_64.zip, unzip it and replace the tla2tools.jar with the latest version (click here to download).
Click and download https://lamport.azurewebsites.net/tla/tutorial/original-specs.zip, unzip and save a copy to a folder you will experiment with.
- There are several "click here"s not working. Don't be panic. :)
- add "Sequences" at line 2: EXTENDS Integers, Sequences
- Otherwise, when following 2.4 Tuples at Session 1, you will see 1 error in Expression: detected Unknown operator: `Len'.
Go to https://lamport.azurewebsites.net/tla/tutorial/session1.html. The tutorial is very detailed and easy to follow.
https://lamport.azurewebsites.net/tla/tutorial/contents.html
- For multiple expressions to evaluate together, we can use the built-in array syntax.
- For Goldbach's conjecture verification,
\A k \in Nat : k > 1 => (\E a, b \in 2..(2 * k - 1): IsPrime(a) /\ IsPrime(b) /\ a + b = 2 * k)0..100: only took 5 secs to evaluate as TRUE.0..1000: took 17.3 hours to have result as TRUE.
- Variable assignment is value passing, not reference passing.
- Property-driven development (PDD) naturally fits here.
- Shortcut during debugging from error messages: (Control click) == (click) + (F10)
- Sometimes you will find the model checking doesn't return anything. It is possible the model is created before running a translation at first.