Time to start over… again…

A while back, I posted I was unhappy with the editing facilities of the blogging site I was using at the time. I worked with it anyway trying a few different solutions including using Jekyll, using Org-Mode's export to HTML and tinkering with that, just typing using the built-in HTML editor, and finally trying to use elisp to use the Blogger API. That was a fantastic disaster which I won't go into here, lets just say after about four hours of just trying to get authenticated using the oauth2 elisp library and Google's ideas of how that should work, I rage quit and went to read a book.

It was just too painful to get anything done with that site, so I posted a question on reddit and received several very good answers. I am truly grateful for the Emacs community on reddit. My experience there has always been positive with very helpful people. One comment suggested using writefreely.el as the simplest solution. That comment also suggested Weblorg which I tried and generally liked, but after a couple of hours I realized I still had a long way to go before I would have a working solution, and I went back to try WriteFreely.

Okay, that was dead simple to use. The writefreely package in Emacs just works, the result looks good and it took almost two minutes of my time to setup and another 30 minutes of tinkering with a few things to make sure I understood them and tweak my configuration (which is nothing more than a snippet to start my org file). So, props to pxoq for the great suggestions. Also thanks to the other comments left by other users, I did mindfully read and research all of them.

If you are looking for some approaches to blogging, writing posts in Emacs and publishing them somewhere on the web, read through the comments on that reddit post, there are some truly great and simple approaches offered. Much thanks to all of them for responding.

Tags: #writefreely #emacs

The problem…

A friend of mine sent a request on Slack today, he asked if anyone had tried to solve a particular problem he had found posted on twitter. The post references this GitHub page where the problem and some of the solutions are described. My friend specifically asked if anyone had solved this with pure DataWeave, a transformation language embedded in the MuleSoft software known as Mule.

I haven't coded anything in DataWeave for quite a while, so I thought I'd give it a go. I had to read up on some of the functions, and then use this REPL to do the work. I copied the example input from the GitHub page, and started hacking away.

A first pass…

At first I thought I could use some nifty recursion and a “stream” data structure. Basically, that is a pair, the first part is the current value, the second is a function which returns a pair with the next value and a function. That didn't work out because, well, recursion. DataWeave is not tail-call optimized and will overflow the stack at 256 frames.

Bummer.

A second pass…

Okay, so looking at it from a different perspective, I just needed to setup the indices correctly and then I could iterate over the payload and come up with a solution.

%dw 2.0
output application/json
var allWithReset = zip(payload map $.reset_lesson_position,  payload.lessons map $$ )
var allStartVals = allWithReset map if ($[0] == true) 0 else $[1] + $[1]
---
payload map (value, index) -> {
    title: value.title,
    reset_lesson_position: value.reset_lesson_position,
    position: index + 1,
    lessons: value.lessons map {
        name: $.name,
        pos: allStartVals[index] + ($$ + 1)
    }
}

That did the trick… with the 3 records in the example data set. But I decided to add another record. And, well, you can guess what happened next… yep, the indices were off – completely. Obviously, the problem is how I was creating the indices, so let's look there for a solution:

%dw 2.0
output application/json
var allWithReset = zip(payload map $.reset_lesson_position,  payload.lessons map $$ )
var allStartVals = allWithReset map if ($[0] == true) 0 else $[1] + $[1]
var allStartNormalized = allStartVals map if (allStartVals[$$ - 1] == 0) 2 else allStartVals[$$]
---
payload map (value, index) -> {
    title: value.title,
    reset_lesson_position: value.reset_lesson_position,
    position: index + 1,
    lessons: value.lessons map {
        name: $.name,
        pos: allStartNormalized[index] + ($$ + 1)
    }
}

Yep, that fixed it! Well, at least until I added another record and changed one of the reset values… And then the indices are broken again. So, the solution is just to add more complexity, right!??!

%dw 2.0
output application/json
var allWithReset = zip(payload map $.reset_lesson_position,  payload.lessons map $$ )
var allStartVals = allWithReset map if ($[0] == true) 0 else $[1] + $[1]
var allStartNormalized = allStartVals map 
    if (allStartVals[$$ - 1] == 0 and allStartVals[$$] == 0) 
        0 
    else if (allStartVals[$$ - 1] == 0 and allStartVals[$$] != 0) 
        2 
    else allStartVals[$$]
---
payload map (value, index) -> {
    title: value.title,
    reset_lesson_position: value.reset_lesson_position,
    position: index + 1,
    lessons: value.lessons map {
        name: $.name,
        pos: allStartNormalized[index] + ($$ + 1)
    }
}

Nope, that fails too. At this point I start getting a little banter in the slack channel. We discuss the merits of different approaches to a solution, then one of my friends posts a working solution that is elegant and, after thinking about it, somewhat obvious. As a matter of fact, after saying recursion several times, I realized I needed to be reaching for the reduce function, which is how DataWeave manages recursion.

The solution…

Nope, not going to post it here, you'll have to go read this blog post to get the answer. This guy writes some nice blog posts as well, so feel free to peruse and learn a few things. Good stuff!!

Tags: #MuleSoft #Dataweave