welder

Welder

Welder allows you to define pipelines in a true Unix style.

It provides a simple and powerful DSL to define you own pipelines and compose them together. You can define a pipeline out of one or more ruby callables:

read_file = ->(filename) { File.read(filename) }
count_words = ->(text) { text.split.size }

count_words_from_file = Welder::Pipeline.new | read_file | count_words  # Define a pipeline
puts "My book has #{'my_book.txt' | count_words_from_file} words"       # Execute it with a specific value

Note that, for the pipe operator to work, the first argument has to be a Welder::Pipeline

Why pipelines?

In some use cases, pipelines have several advantages over the natural, imperative style of languages like ruby. Take, for instance, the following example:

puts "My book has #{'my_book.txt' | read_file | count_words} words"

Here, the alternative way to write the word count would be count_words(read_file('my_book.txt')). Pipelines, in contrast:

• Provide a cleaner syntax that is better at expressing the statement's order and intent
• Ease the instrumentation of the whole process (e.g. for debugging and benchmarking purposes)
• Allow for ways to abstract the way the different stages in the pipeline are called. For instance, creating pipelines of remote methods using RPC

Valves

Valves are callables that get called at every step of a pipeline with the input to the step, the function processing it, and the generated output. Valves are useful for logging, debugging and code instrumentation. You set valves like this:

logged_steps = []
log = ->(i, l, o) { logged_steps << "Executed step #{l.inspect} with input=#{i.inspect} and got #{o.inspect}" }
count_words_and_log_steps = (Welder::Pipeline.new | read_file | count_words) -log

'my_book.txt' | count_words_and_log_steps
puts logged_steps.size  # => 2
puts logged_steps[0]    # Executed step "..." with input="my_book.txt" and output="this is my book"
puts logged_steps[1]    # Executed step "..." with input="this is my book" and output=4

Present and Future

The next step for Welder will be getting a nice toolbelt to start his work (extra gems with useful pipelines our of the box)

Contributing to Welder

Welder is open for help in any way.

License

See LICENSE file