Walkthrough: multi

Source walkthrough from src-doc/walkthrough/std_lang_01_multi.clj

This page promotes the existing walkthrough source into the public Hara docs. The implementation source remains in src-doc/walkthrough/std_lang_01_multi.clj; this page explains the intent and links it to the surrounding Hara layers.

1 Motivation

The walkthrough shows how hara.lang scripts define target contexts, how forms are emitted or executed, and how generated pointers connect Clojure authoring to target language code.

2 How to use it

Read the source file directly for the executable facts. The docs page keeps high-level explanation here and uses selected fact snippets below.

3 Walkthrough

3.1 JavaScript context

l/script- :js installs a JavaScript book into the current namespace. !.js evaluates a form and returns emitted JS; defn.js stores a function entry.

emit JS from a script context

^{:refer hara.lang/script- :added "4.0"}
(l/script- :js
  {:require [[xt.lang.spec-base :as xt]]})
(!.js (+ 1 2 3))
=> "1 + 2 + 3"

(defn.js hello []
  (return (+ 1 2 3)))
(l/emit-ptr hello)
=> "export function hello(){\n  return 1 + 2 + 3;\n}"

3.2 Lua context

l/script- :lua does the same for Lua. The same hara.lang form now produces Lua syntax.

emit Lua from a script context

^{:refer hara.lang/script- :added "4.0"}
(l/script- :lua
  {:require [[xt.lang.spec-base :as xt]]})
(!.lua (+ 1 2 3))
=> "1 + 2 + 3"

(defn.lua world []
  (return (+ 1 2 3)))
(l/emit-ptr world)
=> "local function world()\n  return 1 + 2 + 3\nend"

3.3 Python and R contexts

The same pattern extends to Python and R. Each runtime has its own book, module, and emitted syntax.

emit Python from a script context

^{:refer hara.lang/script- :added "4.0"}
(l/script- :python
  {:require [[xt.lang.spec-base :as xt]]})
(!.py (+ 1 2 3))
=> "1 + 2 + 3"

(defn.py again []
  (return (+ 1 2 3)))
(l/emit-ptr again)
=> "def again():\n  return 1 + 2 + 3"

emit R from a script context

^{:refer hara.lang/script- :added "4.0"}
(l/script- :r
  {:require [[xt.lang.spec-base :as xt]]})
(!.R (+ 1 2 3))
=> "1 + 2 + 3"

(def.R stuff
  (fn []
    (return (+ 1 2 3))))
(l/emit-ptr stuff)
=> "stuff <- function (){\n  return(1 + 2 + 3);\n};"

3.4 Multiple contexts in one namespace

l/script+ creates additional named contexts when you need more than one runtime of the same language in a namespace. The first argument is a [env-name language] vector.

create two Python contexts and two JS contexts

^{:refer hara.lang/script+ :added "4.0"}
(l/script+ [:env1 :python]
  {:require [[xt.lang.spec-base :as xt]]})
(l/script+ [:env2 :js]
  {:require [[xt.lang.spec-base :as xt]]})
[(l/! [:env1]
   (fn [] (return (+ 1 2 3))))
 (l/! [:env2]
   (fn [] (return (+ 1 2 3))))]
=> ["lambda *__args : 1 + 2 + 3"
    "function (){\n  return 1 + 2 + 3;\n}"]

4 Source

(l/script- :js
  {:require [[xt.lang.spec-base :as xt]]})

js runtime

^:hidden
  
(!.js
 (+ 1 2 3))
=> "1 + 2 + 3;"

(defn.js hello
  []
  (return
   (+ 1 2 3)))

(l/emit-ptr hello)
=> "function hello(){\n  return 1 + 2 + 3;\n}"

(str hello)
=> (std.string/|
    "![:lang/js :default walkthrough.hara.lang-01-multi/hello :code]"
    "function hello(){"
    "  return 1 + 2 + 3;"
    "}")

(l/script- :lua
  {:require [[xt.lang.spec-base :as xt]]})

lua runtime

^:hidden
  
(!.lua
 (+ 1 2 3))
=> "1 + 2 + 3"

(defn.lua world
  []
  (return
   (+ 1 2 3)))

(l/emit-ptr world)
=> "local function world()\n  return 1 + 2 + 3\nend"

(str world)
=> (std.string/|
    "![:lang/lua :default walkthrough.hara.lang-01-multi/world :code]"
    "local function world()"
    "  return 1 + 2 + 3"
    "end")

(l/script- :python
  {:require [[xt.lang.spec-base :as xt]]})

python runtime

^:hidden
  
(!.py
 (+ 1 2 3))
=> "1 + 2 + 3"

(defn.py again
  []
  (return
   (+ 1 2 3)))
  
(l/emit-ptr again)
=> "def again():\n  return 1 + 2 + 3"

(str again)
=> (std.string/|
    "![:lang/python :default walkthrough.hara.lang-01-multi/again :code]"
    "def again():"
    "  return 1 + 2 + 3")

(l/script- :r
  {:require [[xt.lang.spec-base :as xt]]})

r runtime

^:hidden
  
(!.R
 (+ 1 2 3))
=> "1 + 2 + 3;"

(def.R stuff
  (fn []
    (return
     (+ 1 2 3))))
  
(l/emit-ptr stuff)
=> "stuff <- function (){\n  return(1 + 2 + 3);\n};"

(str stuff)
=> (std.string/|
    "![:lang/r :default walkthrough.hara.lang-01-multi/stuff :code]"
    "stuff <- function (){"
    "  return(1 + 2 + 3);"
    "};")

(l/script+ [:env1 :python]
  {:require [[xt.lang.spec-base :as xt]]})


(l/! [:env1]
  (fn [] (return (+ 1 2 3))))
=>

(lambda : 1 + 2 + 3)

(l/script+ [:env2 :js]
  {:require [[xt.lang.spec-base :as xt]]})

(l/! [:env2]
  (fn [] (return (+ 1 2 3))))
=>

function (){n return 1 + 2 + 3;n}