alt Hacker NewsThe "aliases not pointers" approach for memory safety is interesting. Curious how you handle the performance implications - traditional aliasing analysis in compilers is expensive because determining whether two aliases point to the same memory is hard.
Are you doing this at runtime (reference counting or similar), or have you found a way to make the static analysis tractable by restricting what aliasing patterns are allowed?
The 250kB size is impressive for a language with inheritance and N-dimensional arrays. For comparison, Lua's VM is around 200-300kB and doesn't include some of those features. What did you have to leave out to hit that size? I assume no JIT, but what about things like regex, IO libraries, etc?
Also - calling back into C functions from the script is a key feature for embeddability. How do you handle type marshalling between the script's type system and C's? Do you expose a C API where I register callbacks with type signatures, or is there reflection/dynamic typing on the boundary?
Good questions! The short answer to the first is that the language is interpreted, not compiled, so optimizations are moot.
Aliases are strongly-typed which helps avoid some issues. Memory mods come with the territory —- if ‘a’ and ‘b’ point to the same array and ‘a’ resizes that array, then the array behind ‘b’ gets resized too. The one tricky situation is when ‘a’ and ‘b’ each reference range of elements, not the whole array, because a resize of ‘a’ would force a resize of the width of ‘b’. Resizing in this case is usually not allowed.
Garbage collection is indeed done (poorly) by reference counting, and also (very well) by a tracing function that Cicada’s command line script runs after every command.
You’re exactly right, the library is lean because I figure it’s easy to add a C function interface for any capability you want. There’s a bit of personal bias as to what I did include - for example all the basic calculator functions are in, right down to atan(), but no regex. Basic IO (save, load, input, print) is included.
Type marshaling — the Cicada int/float types are defined by cicada.h and can be changed! You just have to use the same types in your C code.
When you run Cicada you pass a list of C functions paired with their Cicada names: { “myCfunction”, &myCfunction }. Then, in Cicada, $myCfunction() runs the callback.
Thanks for the questions! This is exactly the sort of feedback that helps me learn more about the landscape..