Erlang's approach is non-obvious, and, I believe, correct. In the usual case, Erlang does not use a contiguous chunk of memory to represent a sequence of bytes. This is why template rendering in Ruby, Python, etc. No matter how blocking and concurrent your application logic is, it is impossible to make a blocking network call in Erlang, or to spawn multiple OS processes.
This design decision makes it so that an Erlang server will never crash the operating system. Having lost many nights of sleep to overloaded operating systems at a previous job, I believe that Erlang's concurrency design is correct. I mentioned that refactoring Erlang code is a pain. Fortunately, in my experience it is rarely necessary to refactor Erlang code in the same way the object-oriented code needs refactoring from time to time.
In Erlang, each function is passed all the information it needs, and you get a compiler warning if it was passed any information it doesn't need. In some sense, refactoring is integrated into development; it is not a distinct activity requiring bountiful test coverage and several pots of coffee.
Refactoring Java or Objective-C code usually becomes necessary because too many instance methods have been added to a class, and the developer must spend time figuring out which methods require which instance variables and how to best cut the carriage in half. This is simply not a concern in functional programming; moving a function to a different module requires very little hand-wringing and virtually no effort.
There is not much mental effort involved; however, due to Erlang's syntactic peculiarities, it can be tedious converting anonymous functions to named functions. Perhaps a clever IDE will eliminate this tedium one day. All data structures in Erlang are completely transparent. Knowing nothing about the library you are using, you can always inspect the contents of data structures at run-time.
This feature greatly aids in debugging, and is a boon to old-fashioned hacking. This page was last modified , 31 August CZ is free. Click here to join and contribute. CZ thanks our previous donors. Either: A - New page has been created, or subpages template was added to an existing page B - Cluster move is in progress Click either the A or B link for further instructions.
A - For a New Cluster use the following directions Subpages format requires a metadata page. Click the blue "metadata template" link below to create the page. You might also fill out the checklist part of the form.
Ignore the rest. For background, see Using the Subpages template Don't worry--you'll get the hang of it right away. View code. An implementation that is highly compatible with Django's own version. Developers should be able to switch between Python and Erlang without touching their web templates. That's the goal. What's Done? Note that the 'load' tag isn't implemented yet, and the API related to custom tags and filters will likely to change when it is.
To use records you will need to inform the etcher application about these records in advance. A parser takes a list of tokens and arranges them into a tree structure called a parse tree. Same idea here. We have some help in the form of a parser generator called Yecc. Yecc is like yacc but for Erlang.
Our Yecc file looks like this. It has three parts: a list of non-terminals, a list of terminals, and a list of rules. Non-terminals are things you can expand into a list of terminals and non-terminals. Terminals cannot be expanded. Using the rules , we expand all the non-terminals into terminals. Here are the rules. At the highest level, we just put things into a list:. Finally, some terminals. As you can see below, the part after the colon is strictly optional.
In that case, nothing gets added to the parse tree. We do need to compile the Yecc file into Erlang code. In total the Yecc file for ErlyDTL weighs in at about lines, roughly the same length as the scanner.
Well kind of. Now we have a parse tree. What we want to do is turn it into Erlang code.
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