String replace on async lambda

[jcubic]

I was working on the $ interpolation syntax extension (right now it needs to be #$), the code needs to look like this:

(define-macro (interpolate str)
  (typecheck "interpolate" str "string")
  (let ((values (gensym "values"))
        (_str (gensym "str"))
        (promises (gensym "promises"))
        (re (gensym "re")))
    `(let ((,promises (vector))
           (,re #/\$\{([^\}]+)\}/)
           (,_str ,str))
       (--> ,_str (replace ,re (lambda (_ expr)
                                 (let ((value '>(eval (read expr))))
                                   (--> ,promises (push value))))))
       (let ((,values (await (Promise.all ,promises))))
         (--> ,_str (replace ,re (lambda (_ expr)
                                   (--> ,values (shift)))))))))

The problem is that the eval code is async and you need to do gimmicks like quoting promises and using await with Promise.all to get the values.

The code is based on an idea from this StackOverflow JavaScript Q&A: javascript : Async/await in .replace.

What needs to be done:

• Document as one of the problems with async code (together with Array::forEach)
• Update replace function
• Document to use replace instead of (--> str (replace (lambda or (str.replace (lambda