proc — first-class callable with railway composition

github.com/go-composites/proc (Go package Proc, imported from the src/ sub-directory) is a first-class callable composite — the org's analogue of Ruby's Proc/lambda. A Proc wraps a single function as a value you can pass around, invoke, and chain. Every Proc is a real object: it never returns a bare nil, it answers IsNull(), and even the Null Proc is safe to Call. Chaining with Then is railway-oriented — it short-circuits on an error result.

API

import Proc "github.com/go-composites/proc/src"

type Interface interface {
    Call(args ...interface{}) Result.Interface
    Then(next Interface) Interface
    IsNull() bool
}

func New(fn func(args ...interface{}) Result.Interface) Interface
func Null() Interface

• New(fn) wraps fn as a Proc. If fn is nil the resulting Proc is still safe — Call returns an error Result rather than panicking.
• Null() returns the Null-Object (not-callable) Proc (see below).

Member	Behaviour
Call(args...)	Invokes the wrapped function with the given arguments and returns its Result. A Proc whose wrapped function is nil does not panic — it returns an Error.New("Proc.Call: nil function") Result.
Then(next)	Returns a new Proc that calls the receiver and, on a successful Result, feeds that result's payload as the single argument to next.Call. If the receiver yields an error Result, Then short-circuits and returns that error unchanged — next is never called.
IsNull()	Returns false for an ordinary Proc, true for the Null() one.

Usage

double := Proc.New(func(args ...interface{}) Result.Interface {
    n := args[0].(int)
    return Result.New(Result.WithPayload(n * 2))
})

incr := Proc.New(func(args ...interface{}) Result.Interface {
    n := args[0].(int)
    return Result.New(Result.WithPayload(n + 1))
})

// Railway composition: double then incr.
if r := double.Then(incr).Call(5); !r.HasError() {
    fmt.Println(r.Payload()) // 11
}

The Null-Object variant

Proc.Null() is not callable: Call returns an Error.New("Proc.Null: not callable") Result, Then returns the Null Proc again (so chains stay on the null), and IsNull() returns true.

Dependencies

proc depends on result and error (and transitively on null).