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At the first annual charity event conducted by Puget Sound Programming Python (PuPPy) last Tuesday, four legendary language creators came together to discuss the past and future of language design. This event was organized to raise funds for Computer Science for All (CSforALL), an organization which aims to make CS an integral part of the educational experience.

Among the panelists were the creators of some of the most popular programming languages:

  • Guido van Rossum, the creator of Python
  • James Gosling, the founder, and lead designer behind the Java programming language
  • Anders Hejlsberg, the original author of Turbo Pascal who has also worked on the development of C# and TypeScript
  • Larry Wall, the creator of Perl

The discussion was moderated by Carol Willing, who is currently a Steering Council member and developer for Project Jupyter. She is also a member of the inaugural Python Steering Council, a Python Software Foundation Fellow and former Director.

Key principles of language design

The first question thrown at the panelists was, “What are the principles of language design?” Guido van Rossum believes:


Designing a programming language is very similar to the way JK Rowling writes her books, the Harry Potter series.

When asked how he says JK Rowling is a genius in the way that some details that she mentioned in her first Harry Potter book ended up playing an important plot point in part six and seven.

Explaining how this relates to language design he adds, “In language design often that’s exactly how things go”. When designing a language we start with committing to certain details like the keywords we want to use, the style of coding we want to follow, etc. But, whatever we decide on we are stuck with them and in the future, we need to find new ways to use those details, just like Rowling.

The craft of designing a language is, in one hand, picking your initial set of choices so that’s there are a lot of possible continuations of the story. The other half of the art of language design is going back to your story and inventing creative ways of continuing it in a way that you had not thought of,” he adds.

When James Gosling was asked how Java came into existence and what were the design principles he abided by, he simply said, “it didn’t come out of like a personal passion project or something. It was actually from trying to build a prototype.” James Gosling and his team were working on a project that involved understanding the domain of embedded systems. For this, they spoke to a lot of developers who built software for embedded systems to know how their process works.

This project had about a dozen people on it and Gosling was responsible for making things much easier from a programming language point of view. “It started out as kind of doing better C and then it got out of control that the rest of the project really ended up just providing the context”, he adds. In the end, the only thing out of that project survived was “Java”. It was basically designed to solve the problems of people who are living outside of data centers, people who are getting shredded by problems with networking, security, and reliability.

Larry Wall calls himself a “linguist” rather than a computer scientist. He wanted to create a language that was more like a natural language. Explaining through an example, he said, “Instead of putting people in a university campus and deciding where they go we’re just gonna see where people want to walk and then put shortcuts in all those places.” A basic principle behind creating Perl was to provide APIs to everything. It was aimed to be both a good text processing language linguistically but also a glue language.

Wall further shares that in the 90s the language was stabilizing, but it did have some issues. So, in the year 2000, the Perl team basically decided to break everything and came up with a whole new set of design principles. And, based on these principles Perl was redesigned into Perl 6. Some of these principles were picking the right default, conserve your brackets because even Unicode does not have enough brackets, don’t reinvent object orientation poorly, etc.

He adds,

“A great deal of the redesign was to say okay what is the right peg to hang everything on? Is it object-oriented? Is it something in the lexical scope or in the larger scope? What does the right peg to hang each piece of information on and if we don’t have that peg how do we create it?”

Anders Hejlsberg shares that he follows a common principle in all the languages he has worked on and that is “there’s only one way to do a particular thing.” He believes that if a developer is provided with four different ways he may end up choosing the wrong path and realize it later in the development. According to Hejlsberg, this is why often developers end up creating something called “simplexity” which means taking something complex and wrapping a single wrapper on top it so that the complexity goes away.

Similar to the views of Guido van Rossum, he further adds that any decision that you make when designing a language you have to live with it. When designing a language you need to be very careful about reasoning over what “not” to introduce in the language. Often, people will come to you with their suggestions for updates, but you cannot really change the nature of the programming language. Though you cannot really change the basic nature of a language, you can definitely extend it through extensions. You essentially have two options, either stay true to the nature of the language or you develop a new one.

The type system of programming languages

Guido van Rossum, when asked about the typing approach in Python, shared how it was when Python was first introduced. Earlier, int was not a class it was actually a little conversion function. If you wanted to convert a string to an integer you can do that with a built-in function. Later on, Guido realized that this was a mistake. “We had a bunch of those functions and we realized that we had made a mistake, we have given users classes that were different from the built-in object types.

That’s where the Python team decided to reinvent the whole approach to types in Python and did a bunch of cleanups. So, they changed the function int into a designator for the class int. Now, calling the class means constructing an instance of the class.

James Gosling shared that his focus has always been performance and one factor for improving performance is the type system. It is really useful for things like building optimizing compilers and doing ahead of time correctness checking. Having the type system also helps in cases where you are targeting small footprint devices. “To do that kind of compaction you need every kind of hope that it gives you, every last drop of information and, the earlier you know it, the better job you do,” he adds.

Anders Hejlsberg looks at type systems as a tooling feature. Developers love their IDEs, they are accustomed to things like statement completion, refactoring, and code navigation. These features are enabled by the semantic knowledge of your code and this semantic knowledge is provided by a compiler with a type system. Hejlsberg believes that adding types can dramatically increase the productivity of developers, which is a counterintuitive thought.

We think that dynamic languages were easier to approach because you’ve got rid of the types which was a bother all the time. It turns out that you can actually be more productive by adding types if you do it in a non-intrusive manner and if you work hard on doing good type inference and so forth,” he adds.

Talking about the type system in Perl, Wall started off by saying that Perl 5 and Perl 6 had very different type systems. In Perl 5, everything was treated as a string even if it is a number or a floating point. The team wanted to keep this feature in Perl 6 as part of the redesign, but they realized that “it’s fine if the new user is confused about the interchangeability but it’s not so good if the computer is confused about things.

For Perl 6, Wall and his team envisioned to make it a better object-oriented as well as a better functional programming language. To achieve this goal, it is important to have a very sound type system of a sound meta object model underneath. And, you also need to take the slogans like “everything is an object, everything is a closure” very seriously.

What makes a programming language maintainable

Guido van Rossum believes that to make a programming language maintainable it is important to hit the right balance between the flexible and disciplined approach. While dynamic typing is great for small programs, large programs require a much-disciplined approach. And, it is better if the language itself enables that discipline rather than giving you the full freedom of doing whatever you want. This is why Guido is planning to add a very similar technology like TypeScript to Python. He adds:

“TypeScript is actually incredibly useful and so we’re adding a very similar idea to Python. We are adding it in a slightly different way because we have a different context.”

Along with type system, refactoring engines can also prove to be very helpful. It will make it easier to perform large scale refactorings like millions of lines of code at once. Often, people do not rename methods because it is really hard to go over a piece of code and rename exactly this right variable. If you are provided with a refactoring engine, you just need to press a couple of buttons, type in the new name, and it will be refactored in maybe just 30 seconds.

The origin of the TypeScript project was these enormous JavaScript codebases. As these codebases became bigger and bigger, it became quite difficult to maintain them. These codebases basically became “write-only code” shared Anders Hejlsberg. He adds that this is why we need a semantic understanding of the code, which makes refactoring much easier. “This semantic understanding requires a type system to be in place and once you start adding that you add documentation to the code,” added Hejlsberg. Wall also supports the same thought that “good lexical scoping helps with refactoring”.

The future of programming language design

When asked about the future of programming design, James Gosling shared that a very underexplored area in programming is writing code for GPUs. He highlights the fact that currently, we do not have any programming language that works like a charm with GPUs and much work is needed to be done in that area.

Anders Hejlsberg rightly mentioned that programming languages do not move with the same speed as hardware or all the other technologies. In terms of evolution, programming languages are more like maths and the human brain. He said, “We’re still programming in languages that were invented 50 years ago, all of the principles of functional programming were thought of more than 50 years ago.”

But, he does believe that instead of segregating into separate categories like object-oriented or functional programming, now languages are becoming multi-paradigm.

“Languages are becoming more multi-paradigm. I think it is wrong to talk about oh I only like object-oriented programming, or imperative programming, or functional programming language.”

Now, it is important to be aware of the recent researches, the new thinking, and the new paradigms. Then we need to incorporate them in our programming style, but tastefully.

Watch this talk conducted by PuPPy to know more in detail.

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