kont v0.1.3 — Unified marker pool and UnwindFrame

[hayabusa-cloud]

Introduction

The kont package implements delimited continuations and algebraic effects for Go 1.26+. It provides two computation representations: Cont[R, A] (closure-based CPS) and Expr[A] (defunctionalized frame chains evaluated by an iterative trampoline). Effect handlers use F-bounded polymorphism for compile-time dispatch. The stepping API (StepExpr, Suspension) enables external runtimes such as proactor event loops to drive computation one effect at a time.

Usage

Downstream packages can use UnwindFrame for allocation-free fused constructors:

func loopUnwind[S, A any](data, _, _, current kont.Erased) (kont.Erased, kont.Frame) {
    step := data.(func(S) kont.Expr[kont.Either[S, A]])
    e := current.(kont.Either[S, A])
    if left, ok := e.GetLeft(); ok {
        result := ExprLoop(left, step)
        return kont.Erased(result.Value), result.Frame
    }
    right, _ := e.GetRight()
    return kont.Erased(right), kont.ReturnFrame{}
}

uf := kont.AcquireUnwindFrame()
uf.Data1 = step
uf.Unwind = loopUnwind[S, A]

Highlights

Unified marker pool reduces Cont-path memory allocations. UnwindFrame provides a cache-line-sized (64 bytes on amd64) data-oriented frame with direct type-switch dispatch, enabling downstream fused constructors without closure allocation.

What's Changed

Features

• Unified marker pool: replace four typed markers (effectMarker, bindMarker, thenMarker, mapMarker) with a single genericMarker backed by sync.Pool, parameterized by static function pointers (feat: unified marker pool and UnwindFrame #6)
• UnwindFrame: data-oriented frame with 3 erased data fields + function pointer, dispatched via direct type-switch in evalFrames (feat: unified marker pool and UnwindFrame #6)
• AcquireUnwindFrame(): pool acquisition for UnwindFrame (feat: unified marker pool and UnwindFrame #6)

Compatibility

• Go: 1.26+

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This discussion was created from the release kont v0.1.3 — Unified marker pool and UnwindFrame.