On Thursday, April 23, 2015 at 2:36:45 PM UTC-5, Kuba Roth wrote:
>
> This is my first time writing macros in Julia. I've read related docs but
> could not find an example which works with the arbitrary number of
> arguments.
> So in my example below the args... works correctly with string literals
> but for the passed variables it returns their names and not the values.
Here's the result of the last thing you called (note that I don't even have
testB and testC defined!)
julia> macroexpand(:(@echo testB testC))
:(for #6#x = (:testB,:testC) # line 3:
print(#6#x," ")
end)
What ends up in `args` is the argument tuple to the macro. Typically, you
wouldn't process that in the final output--otherwise you could just use a
function! Instead, you'd splice each argument individually (`$(args[1])`,
`$(args[2])`, etc.) using a loop in the macro body, with each element of
the loop emitting more code, then gluing the pieces together at the end.
Style notes: Typically, no space between function/macro name and formal
arguments list. Multiline expressions are easier to read in `quote`/`end`
blocks.
Anyways, here's one way to do sort of what you want in a way that requires
a macro (though I still wouldn't use one for this! Didactic purposes only!):
macro unrolled_echo(args...)
newxpr = Expr(:block) # empty block to hold multiple statements
append!(newxpr.args, [:(print($arg, " ")) for arg in args]) # the
arguments to the :block node are a list of Exprs
newxpr # return the constructed expression
end
