I've got that book, it is interesting to read. I also spent quite a bit of time looking at the Oberon system and that has been very educational. Oberon is quite like Pascal, but in some ways simplified even more. He wrote a complete operating system and user interface in Oberon and it is just amazing how much he achieved with very few lines of code.
I'm currently attempting to write a C compiler and the complexity is incredible compared to Oberon or Pascal. Sometimes I regret choosing C over Pascal as I'd probably be done now with the compiler, as it is I've only got the parser and preprocessor implemented.
Eiffel is another language that didn't gain a lot of popularity but is very interesting to read about. Bertrand Meyer, the creator of Eiffel is now at ETH Zurich, where Wirth spent most of his career. It's a very nice language that didn't achieve a lot of popularity, but some of the ideas, such as preconditions and postconditions, have been used in other systems.
I've written an Object Pascal (the current incarnation that Delphi/FreePascal uses) compiler/transpiler for Object Pascal->JavaScript and yes, it's great language for compiler writers because the language makes the job of the compiler so easy. You have to really go out of your way to make the compilation slow, and there aren't a lot of undefined behaviors or other gotchas that are hard to navigate. Also, I wrote it in Delphi. :-)
I'm currently attempting to write a C compiler and the complexity is incredible compared to Oberon or Pascal. Sometimes I regret choosing C over Pascal as I'd probably be done now with the compiler, as it is I've only got the parser and preprocessor implemented.
Eiffel is another language that didn't gain a lot of popularity but is very interesting to read about. Bertrand Meyer, the creator of Eiffel is now at ETH Zurich, where Wirth spent most of his career. It's a very nice language that didn't achieve a lot of popularity, but some of the ideas, such as preconditions and postconditions, have been used in other systems.