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65 lines
3.8 KiB
Markdown
65 lines
3.8 KiB
Markdown
# Thoughts
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A collection of thoughts and todo tasks for the project.
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- Remove the concept of 'Ast node'. While providing fine-grained source mapping is
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is reasonably useful, it complicates the implementation of macros and other source
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transforming operations. Instead, we can key collection types (which have the unique
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pointer property) to source mapping information in a external data structure, which is specifically
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for source mapping. This data structure would be a hash table that used pointer equality
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instead of value equality for entries.
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The compiler would then need to keep track of 'most specific collection' node when compiling,
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as the value itself would not always be a collection and contain source mapping information.
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As a result, we could remove special forms like 'ast-quote', as well as ast-unwrapping logic
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which potentially duplicates a fair amount of data. Macros would be easier to write without
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needing to either unwrap ast values or sacrifice all source mapping.
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- Serialization and deserialization of all datatypes. This would allow loading of bytecode
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without needing the compiler present. However, loading C functions is currently problematic.
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C functions could perhaps be wrapped in data structures that contain some meta information
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about them, say home module and types. This could also allow some automated type checking for
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C functions rather than writing it manually. Some slight overhead could perhaps be compensated
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for by adding optional ommission of typechecking later for C functions if it can be statically
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shown the types are sound.
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- Better support for custom user datatypes. Tables and structs do work well for creating
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custom 'objects' and records, but lack ability to differentiate between object style
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values and data structure style values. For example, simply adding special keys as fields
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would make plain a table or struct possibly become object-like if the write keys are added.
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A Lua like solution would be metatables. It would perhaps make sense to only allow
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metatables on tables, as object like behavior seems to makes most sense on mutable data (?).
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For example, metatables on a struct could allow non-pure behavior unless they were extremely
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limited, or purity was enforced somehow. This could break expectations of a struct to behave
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as immutable data.
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Also, it might make sense that the metatable of a value would actually be a struct, so
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a metastruct. Implementations of Lua (LuaJIT) do not allow (or do not acknowledge)
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changing certain values of a metatables after it is set, such as gc, for performance
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reasons.
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Currently, tables can have a prototype table, which is used to look up values recursively if they
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are not found in the original table. This provides a partial solution to custom user types,
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but does not have the felxibility of Lua style metatables.
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- Actually make a debugger. While the VM changes to enable debugging are relatively
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simple, make a useful debugger would be another project. At first, simply inspection
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of the generated bytecode assembly would be a good start. Single stepping, continuation,
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and inspecting the stack and current fiber would be a start.
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Preferably this would be programmed in dst. The needed functionality could be exposed
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in the fiber API.
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Later, with information from the compiler, we could inspect variables and upvalues
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by symbol. The current compiler does not do full SSA optimization, so named values
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are always accessible in the stack when in scope.
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- Create a pool for fibers. Whlie the general purpose allocator and GC can be made more efficient,
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Fiber's can be well pooled because the allocated stack is large and can be reused. The stack
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size parameter on dst_fiber could simply become the minimum memory allocated for the stack. (Do
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a linear search throught the pool).
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- Implement multi-methods.
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