Region-based memory management

[ichiban]

Since we took advantage of Go's memory management, we have a lot of pointers and interfaces which are pointers disguised.

This also lets us provide an approachable set of APIs, I hope, but comes with a cost of GC because the GC has to trace all the live terms.

type Term interface {
	WriteTerm(w io.Writer, opts *WriteOptions, env *Env) error
	Compare(t Term, env *Env) int
}

We might be able to provide a workable set of APIs while implementing a WAM-like region-based memory management.

type VM struct {
	termCells []termCell
	// ...
}
type Term uint32 // index to termCells

Related issues:

• Idea for an efficient string representation #238
• Memory overflows cannot be caught #226

Some articles that might be related:

• Flattening ASTs (and Other Compiler Data Structures)
• Handles are the better pointers

[ichiban]

Atom may or may not be re-implemented as unique.Handle[string].

New unique package
The new unique package provides facilities for canonicalizing values (like “interning” or “hash-consing”).

Any value of comparable type may be canonicalized with the new Make[T] function, which produces a reference to a canonical copy of the value in the form of a Handle[T]. Two Handle[T] are equal if and only if the values used to produce the handles are equal, allowing programs to deduplicate values and reduce their memory footprint. Comparing two Handle[T] values is efficient, reducing down to a simple pointer comparison.

https://tip.golang.org/doc/go1.23