fble-0.5 (2025-07-13,fble-0.4-212-ga8f8ad0f)
In this tutorial you'll be introduced to the fble programming language, where it comes from, what it's for, and why you should bother learning it.
To understand the origins of fble, you need to know a little about me, the author of this tutorial and the creator of the fble programming language.
I love programming. I program for a living and as a hobby. One of the first questions I ask when starting a new project is what programming language to use for it.
The first programming language I learned was C++, which I learned taking classes in college. I wrote a Javascript interpreter in C++ for the fun of it and started playing around with the TCL scripting language and Java. At some point I started programming in pure C and using Python for scripting. I was introduced to functional programming in graduate school via Bluespec and then Haskell.
The trouble is, none of these languages have everything I'm looking for. I want the simplicity of C, the performance of C and C++, support for generics from C++, Java, and Haskell, automatic memory management from Java and Haskell, the strong type system of Haskell, and the hardware generation capabilities of Bluespec. I don't want the lack of generics in C, the complexity of C++, the verbosity of Java, the performance challenges and obscurity of Haskell, or the awkwardness of writing software in Bluespec.
I decided to see if I could design my own programming language to match my desires, and thus the Fable project was born. I progressed through a series of language prototypes and rewrites: fbla, fblb, fblc, fbld, and at last, where we are today, fble.
Note: "fble" is pronounced as four separate letters f-b-l-e, with stress
on the f: /'ef.biː.el.iː/.
Here is how I think of the fble language.
Start with the simplicity of C. Redesign the foundations from the ground up based on a strong type system and functional programming. Use automatic memory management and make sure there is a clear way to reason about performance. Include support for generics and modularity. Remove as many hard edges, corner cases and redundancies in the language as possible.
The result is a simple, general purpose, statically typed, strict, pure functional programming language with automatic memory management, support for polymorphism and modularity, user-defined primitive data types, and a hint of C-like syntax.
Here are some reasons why you should learn fble:
The fble language represents the collected learnings and perspective gained from my entire experience working with and on programming languages. Learning the fble language is the best way I can share that experience with you.
The fble language is probably one of the simpler pure functional programming languages out there. If you have no former experience with functional programming languages, fble is a great place to start.
The fble language has a number of novel language features, if you're interested in a different perspective on how to program or what's possible in a programming language:
No builtin primitives or data types. This means fble cannot take easy advantage of existing hardware support for 32 or 64 bit integer types, for example. The benefit, though, is that programmers don't have to coerce their programs into a 32/64 bit box to run fast, user defined types are not syntactically disadvantaged compared to builtin data types, and the door is left open for running fble programs on different, novel, and potentially much more efficient future hardware architectures.
A novel type system and treatment of modules that makes types and modules first class programming constructs. This allows you to reuse standard programming abstractions for describing the types and modular structure of your programs.
A novel syntax for user-defined literals.
A simpler, more general syntax than Haskell's do notation for monadic
computation.
There's a chance you may enjoy programming in fble as much as I do. You'll have to learn it first to know for sure.
Because fble is designed to be as simple as possible and doesn't have any builtin primitives or data types, it is well suited for programming language research and alternative interpretations of programs, such as for describing hardware or satisfiability-based search queries.
Programs written in fble are likely more secure than programs written in C, given the strong type system and lack of pointers, arrays, and side effects.
The fble language is still early days. The following are not yet reasons for you to learn fble:
Head over to the Language Features tutorial to
get a quick overview of how the fble programming language compares to other
programming languages.