Initialize stateless context

[borkdude]

Sometimes it's desirable to re-use the same set of options in eval-string for performance reasons, like you can do with eval-string* but without the statefulness. It might be nice to offer an API around this.

This can be achieved right now with:

(def mutable-ctx (sci/init {:preset :termination-safe}))
(def immutable-ctx (update mutable-ctx :env deref))
(defn init-ctx [immutable-ctx] (update immutable-ctx :env atom))
(sci/eval-string* (init-ctx proto-ctx) "(+ 1 2 3)" )
;;=> 6
(sci/eval-string* (init-ctx proto-ctx) "(def x 1) x")
1
(sci/eval-string* (init-ctx proto-ctx) "x")
Execution error (ExceptionInfo) at sci.impl.utils/throw-error-with-location (utils.cljc:54).
Could not resolve symbol: x [at line 1, column 1]

[ikitommi]

did a quick test using criterium:

(ns user
  (:require [criterium.core :as cc]
            [sci.core :as sci]
            [sci.impl.interpreter :as scii]
            [sci.impl.opts :as scio]))

;; 25µs
(cc/quick-bench (sci/eval-string "(+ 1 1)" nil))

(def ctx (update (scio/init nil) :env deref))

;; 13µs
(cc/quick-bench (scii/eval-string* (update ctx :env atom) "(+ 1 1)"))

[borkdude]

@ikitommi Note that eval-string* and init are part of the public API in sci.core.

[borkdude]

Implemented as follows:

In a multi-user environment it can be useful to give each user their own
context. This can already be achieved with eval-string, but for performance
reasons it may be desirable to initialize a shared context. This shared context
can then be forked for each user so that changes in one user's context
aren't visible for other users:

(def forked (sci/fork sci-ctx))
(sci/eval-string* forked "(def forked 1)")
(sci/eval-string* forked "forked") ;;=> 1
(sci/eval-string* sci-ctx "forked") ;;=> Could not resolved symbol: forked