CHANGELOG.md

v0.6

Breaking: The rules for transforming chains were simplified. Before, there was the two-arg block syntax (this was the only syntax originally):

@chain x begin
    y
    z
end

the inline syntax:

@chain x y z

and the one-arg block syntax:

@chain begin
    x
    y
    z
end

All of these are now a single syntax, derived from the rule that any begin ... end block in the inline syntax is flattened into its lines. This means that you can also use multiple begin ... end blocks, and they can be in any position, which can be nice for interactive development of a chain in the REPL.

@chain x y begin
    x
    y
    z
end u v w begin
    g
    h
    i
end

This is only breaking if you were using a begin ... end block in the inline syntax at argument 3 or higher, but you also had to be using an underscore without chaining in that begin block, which is deemed quite unlikely given the intended use of the package. All "normal" usage of the @chain macro should work as it did before.

As another consequence of the refactor, chains now do not error anymore for a single argument form @chain x but simply return x.

v0.5

Breaking: The @chain macro now creates a begin block, not a let block. This means that variables that are assigned within the macro are available outside. Technically, situations are imaginable where this could lead to overwritten variables if someone used large expressions with intermediate variable names in begin blocks spliced into the chain. It is however quite unlikely for the normal way that @chain is intended to be used.

Additionally, it is now possible to use the syntax variable = some_expression to make use of the feature that variables can be exported. The some_expression part is handled exactly like before. This enables you to carry parts of a computation forward to a later step in the chain or outside of it:

@chain df begin
    transform(...)
    select(...)
    intermediate = subset(...)
    groupby(...)
    combine(...)
    join(intermediate)
end

@show intermediate