Processing.js array initialization

Just the other day I fixed a bug for processing.js, where creating an array and initializing it at the same time would crash the parser. What was happening was, code like this:

float[] baz;
baz = new float[] {1.0, 2.5};

when parsed, “new float[]” would be converted to “new ArrayList[]” then “{1.0, 2.5};” would get tacked onto the end, and it shouldn’t. “new ArrayList[]” is only for creating an empty array, without initializing it. If you want to initialize, you want the JavaScript to look like this:

baz = [1.0, 2.5];

notice how I no longer use new ArrayList. ArrayList just isn’t setup for initialization that I could see, but the above method works.

Anyway, I got all this working fine and dandy here.

When the parser came across something with the word “new\s(\w)” which translates to “new” + whitespace + any word, it would package it all up, what I did was added a check for the array contents, ie. everything inside {} it even worked for 2D arrays and beyond. I would then simply replace the whole thing with the array initialization, and later in the parser it would be changed from {} to []. So, whatever the array was, {{1.2, 2.1}, {7.6, 8.8}} for a 2D array, would just replace all {}’s with []. The problem was, and I didn’t notice this until after the patch was submitted, noticed it on the train ride home, was that two arrays can be declared on one line. Sometimes things like this just slip everyone’s minds, there are so many ins and outs of a language, and to translate one language to another you have to have good attention to detail. So, something like this:

baz = new float[][] {{1.0, 2.0}, {3.0, 4.0}}; baz2 = new float[][] {{1.0, 2.0}, {3.0, 4.5}};

would break my fix. It would gobble up the whooole thing into one, and the second “new” would get lost, and cause a syntax error. the fix was pretty easy, and I fixed it one the same train I thought of it on. All I had to do was eat all {}’s and everything inside of them until I hit the semi-colon, then stop! the stop is important, and the part I was lacking before. Before I would gobble it all up until I hit the last semi-colon, so, it was greedy.

Here is the fix. Also, I’ll be fitting this work into my 0.2 release as it’s so very close.

Something else I noticed today (hijacking my own blog post here) working in Processing.js has a pretty big advantage over working in other open source projects. We are a community of developers, so when someone finds a bug, half the time, most of the work in finding the bug is done for us, because the person that found the bug can read the code, and reduce it to a acceptable level of code. But, in a project like Firefox, when a user finds a bug, it might just be a description of what they were doing at the time, and that it crashed. Which is an interesting aspect maybe some of the other members of the processing.js team might not of considered, yet.


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