On Sun, Sep 25, 2016 at 1:09 PM, Jamie Brandon
<ja...@scattered-thoughts.net> wrote:
> Here is some code I just wrote this evening:
>
> n = length(T.parameters)
> index_types = typeof_index(T.parameters)
> pushes = map(1:n) do i
> :(push!(columns[$i], $(Symbol("key_$i"))))
> end
> body = quote $(pushes...) end
> for i in n:-1:1
> body = quote
> $(Symbol("keys_$i")) = collect(keys($(Symbol("index_$i"))))
> sort!($(Symbol("keys_$i")))
> foreach($(Symbol("keys_$i"))) do $(Symbol("key_$i"))
> $(Symbol("index_$(i+1)")) =
> $(Symbol("index_$i"))[$(Symbol("key_$i"))]
> $body
> end
> end
> end
> quote
> columns = tuple($([:(Vector{$(T.parameters[i])}()) for i in 1:n]...))
> index_1 = relation.unique
> $body
> columns
> end
>
> It's split into multiple lines and there's only one comprehension, but it's
> still pretty hard to read and debug. (For example, the first time I ran it I
> got 'syntax: missing comma or ) in argument list' with no line number and
> hand to check each line by hand).
And by split into multiple lines I mean pulling out common parts.
There's no need to call `Symbol` that many times, you can simply do
`keys_names = [Symbol("keys_", i) for i in 1:n]` or `keys_names =
[gensym() for i in 1:n]`
and use `keys_names[i]` everywhere.
There's also no need to use `key_$i`, simply `key` should be enough.
>
> Maybe I could improve the suffixes by writing a macro like:
>
> ip1 = i+1
> body = @suffix quote
> keys_i = collect(keys(index_i))
> sort!(keys_i)
> foreach(keys_i) do key_i
> index_ip1 = index_1[key_i]
> $body
> end
> end
>
> The macros in Base.Cartesian almost solve the comprehension problem too, if
> I make a version that can take arbitrary iters rather than just a number...
>
> On 25 September 2016 at 18:53, Yichao Yu <yyc1...@gmail.com> wrote:
>>
>> On Sun, Sep 25, 2016 at 12:39 PM, Jamie Brandon
>> <ja...@scattered-thoughts.net> wrote:
>> > I'm doing a lot of code-generation. There are two patterns that come up
>> > all
>> > over the place - adding a suffix to a symbol and interpolating from an
>> > array
>> > comprehension. This is pretty verbose even in the simplest case:
>> >
>> > quote
>> > ...
>> > row = tuple($([:($(Symbol("val_$ix))) for ix in order]...))
>> > ...
>> > end
>> >
>> > I spent a fair amount of time tracking down off-by-1-paren typos that
>> > don't
>> > show up until the code is run and behaves weirdly eg
>> > $(Symbol("foo_$ix()"))
>> > vs $(Symbol("foo_$x")()) vs $(Symbol("foo_$x"))()
>> >
>> > Is there a better way of handling this?
>>
>> Split the code into multiple lines.
>
>
