# Macro to generate 2 keyword function parameters
**URL:** https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161
**Category:** General Usage
**Tags:** macros, keyword-arguments
**Created:** [April 17, 2025, 11:05am UTC](https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161 "2025-04-17T11:05:27Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@filchristou](https://discourse.julialang.org/u/filchristou)
#### Post date: [April 17, 2025, 11:05am UTC](https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161/1 "2025-04-17T11:05:27Z")
Let’s say I have this function
```julia
import Dates: DateTime
function myfun1(; ena::Int=1, offsettime::DateTime, entrytime::DateTime, dio::Int)
return nothing
end
```
with the parameters being
```julia
:($(Expr(:parameters, :($(Expr(:kw, :(ena::Int), 1))), :(offsettime::Main.DateTime), :(entrytime::Main.DateTime), :(dio::Int))))
```
I wanted to create a macro that will automate writing `offsetime`, and `entrytime`.
When I do it one by one it works:
```julia
macro recvtime1()
return :($(esc(:offsettime))::DateTime)
end
macro recvtime2()
return :($(esc(:entrytime))::DateTime)
end
function myfun2(; ena=1, @recvtime1, @recvtime2, dio=2)
return nothing
end
```
But when I do it together it complains for what I think is an automatically generated parenthesis:
```julia
macro recvtime()
return :($(esc(:offsettime))::DateTime, $(esc(:entrytime))::DateTime)
end
```
The error:
```julia-repl
julia> function myfun3(; ena=1, @recvtime, dio=2)
return nothing
end
ERROR: syntax: invalid keyword argument syntax "(offsettime::Main.DateTime, entrytime::Main.DateTime)" around REPL[47]:1
Stacktrace:
[1] top-level scope
@ REPL[47]:1
```
Is there a way I can adapt `@recvtime` such that `myfun3` could work as is ?
`@macroexpand` indeed shows the extra parenthesis. I think if I can get them out it should work but I don’t see how.
```julia-repl
julia> @macroexpand @recvtime
:((offsettime::Main.DateTime, entrytime::Main.DateTime))
```
I know I can pass to the macro the whole keyword parameter list and just return an `Expr(:parameters, )` with adding the two keywords, but I prefer not to operate on that level.
---
### Author:  [@eldee](https://discourse.julialang.org/u/eldee)
#### Post date: [April 17, 2025, 2:08pm UTC](https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161/2 "2025-04-17T14:08:16Z")
I would not expect this to be possible, since a macro returns a single `Expr`ession, but you’d need two.
Put differently, compare the ASTs of
```julia-repl
julia> using MacroTools: prewalk, rmlines # To get rid of the line number clutter
julia> ex_macro = prewalk(rmlines, :(function f(@m, c) end)); dump(ex_macro)
Expr
head: Symbol function
args: Array{Any}((2,))
1: Expr
head: Symbol call
args: Array{Any}((3,))
1: Symbol f
2: Expr
head: Symbol macrocall
args: Array{Any}((2,))
1: Symbol @m
2: Nothing nothing
3: Symbol c
2: Expr
head: Symbol block
args: Array{Any}((0,))
```
and
```julia-repl
julia> ex_goal = prewalk(rmlines, :(function f(a, b, c) end)); dump(ex_goal)
Expr
head: Symbol function
args: Array{Any}((2,))
1: Expr
head: Symbol call
args: Array{Any}((4,))
1: Symbol f
2: Symbol a
3: Symbol b
4: Symbol c
2: Expr
head: Symbol block
args: Array{Any}((0,))
```
We need the macro `m` to alter `ex_macro.args[1].args`, while it can only see `ex_macro.args[1].args[2]`.
---
### Author:  [@filchristou](https://discourse.julialang.org/u/filchristou)
#### Post date: [April 17, 2025, 2:20pm UTC](https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161/3 "2025-04-17T14:20:19Z")
Yeah. I had the impression this might be impossible to do. And splatting with `...` doesn’t seem to do the trick as well.
---
### Author:  [@filchristou](https://discourse.julialang.org/u/filchristou)
#### Post date: [April 17, 2025, 3:43pm UTC](https://discourse.julialang.org/t/macro-to-generate-2-keyword-function-parameters/128161/4 "2025-04-17T15:43:57Z")
> I know I can pass to the macro the whole keyword parameter list and just return an `Expr(:parameters, )` with adding the two keywords, but I prefer not to operate on that level.
I ended up passing the whole function to the macro irregardless my preference:
```julia
macro recvtime(funexpr)
parametersdad = funexpr.args[1]
# search
ff = findfirst(ex -> Base.isexpr(ex, :parameters), parametersdad.args)
if isnothing(ff)
newpars = Expr(:parameters, :($(esc(:offsettime))::DateTime), :($(esc(:entrytime))::DateTime) )
insert!(funexpr.args[1].args, 2, newpars)
else
exprpar = parametersdad.args[ff]
newpars = Expr(:parameters, exprpar.args..., :($(esc(:offsettime))::DateTime), :($(esc(:entrytime))::DateTime) )
funexpr.args[1].args[ff] = newpars
end
return funexpr
end
```
Puts the two extra keyword parameters in the function
```julia
julia> @recvtime function myfun3(; ena=1, dio=2)
return nothing
end
```