Split up the functiondef macro

Author: Katharine Hyatt

src/algorithms.jl

@@ -157,66 +157,8 @@ macro algdef(name)
         end)
 end
 
-"""
-    @functiondef [n_args=1] f
-
-Convenience macro to define the boilerplate code that dispatches between several versions of `f` and `f!`.
-By default, `f` accepts a single argument `A`.  This enables the following signatures to be defined in terms of
-the final `f!(A, out, alg::Algorithm)`.
-
-```julia
-    f(A; kwargs...)
-    f(A, alg::Algorithm)
-    f!(A, [out]; kwargs...)
-    f!(A, alg::Algorithm)
-```
-
-The number of inputs can be set with the `n_args` keyword
-argument, so that 
-
-```julia
-@functiondef n_args=2 f
-```
-
-would create 
-
-```julia
-    f(A, B; kwargs...)
-    f(A, B, alg::Algorithm)
-    f!(A, B, [out]; kwargs...)
-    f!(A, B, alg::Algorithm)
-```
-
-See also [`copy_input`](@ref), [`select_algorithm`](@ref) and [`initialize_output`](@ref).
-"""
-macro functiondef(args...)
-    kwargs = map(args[1:end-1]) do kwarg
-        if kwarg isa Symbol
-            :($kwarg = $kwarg)
-        elseif Meta.isexpr(kwarg, :(=))
-            kwarg
-        else
-            throw(ArgumentError("Invalid keyword argument '$kwarg'"))
-        end
-    end
-    isempty(kwargs) || length(kwargs) == 1 || throw(ArgumentError("Only one keyword argument to `@functiondef` is supported"))
-    f_n_args = 1 # default
-    if length(kwargs) == 1
-        kwarg = only(kwargs) # only one kwarg is currently supported, TODO modify if we support more
-        key::Symbol, val = kwarg.args
-        key === :n_args || throw(ArgumentError("Unsupported keyword argument $key to `@functiondef`"))
-        (isa(val, Integer) && val > 0) || throw(ArgumentError("`n_args` keyword argument to `@functiondef` should be an integer > 0"))
-        f_n_args = val
-    end
-
-    f = args[end]
-    f isa Symbol || throw(ArgumentError("Unsupported usage of `@functiondef`"))
-    f! = Symbol(f, :!)
-
-    # TODO is the right way?
-    @gensym A B
-    ex_single_arg = quote
-        # out of place to inplace
+function _arg_expr(::Val{1}, f, f!)
+    return quote # out of place to inplace
         $f(A; kwargs...) = $f!(copy_input($f, A); kwargs...)
         $f(A, alg::AbstractAlgorithm) = $f!(copy_input($f, A), alg)
 
@@ -257,7 +199,10 @@ macro functiondef(args...)
         # copy documentation to both functions
         Core.@__doc__ $f, $f!
     end
-    ex_double_arg = quote
+end
+
+function _arg_expr(::Val{2}, f, f!)
+    return quote
         # out of place to inplace
         $f(A, B; kwargs...) = $f!(copy_input($f, A, B)...; kwargs...)
         $f(A, B, alg::AbstractAlgorithm) = $f!(copy_input($f, A, B)..., alg)
@@ -299,11 +244,65 @@ macro functiondef(args...)
         # copy documentation to both functions
         Core.@__doc__ $f, $f!
     end
-    if f_n_args == 1
-        return esc(ex_single_arg)
-    elseif f_n_args == 2
-        return esc(ex_double_arg)
+end
+
+"""
+    @functiondef [n_args=1] f
+
+Convenience macro to define the boilerplate code that dispatches between several versions of `f` and `f!`.
+By default, `f` accepts a single argument `A`.  This enables the following signatures to be defined in terms of
+the final `f!(A, out, alg::Algorithm)`.
+
+```julia
+    f(A; kwargs...)
+    f(A, alg::Algorithm)
+    f!(A, [out]; kwargs...)
+    f!(A, alg::Algorithm)
+```
+
+The number of inputs can be set with the `n_args` keyword
+argument, so that 
+
+```julia
+@functiondef n_args=2 f
+```
+
+would create 
+
+```julia
+    f(A, B; kwargs...)
+    f(A, B, alg::Algorithm)
+    f!(A, B, [out]; kwargs...)
+    f!(A, B, alg::Algorithm)
+```
+
+See also [`copy_input`](@ref), [`select_algorithm`](@ref) and [`initialize_output`](@ref).
+"""
+macro functiondef(args...)
+    kwargs = map(args[1:end-1]) do kwarg
+        if kwarg isa Symbol
+            :($kwarg = $kwarg)
+        elseif Meta.isexpr(kwarg, :(=))
+            kwarg
+        else
+            throw(ArgumentError("Invalid keyword argument '$kwarg'"))
+        end
+    end
+    isempty(kwargs) || length(kwargs) == 1 || throw(ArgumentError("Only one keyword argument to `@functiondef` is supported"))
+    f_n_args = 1 # default
+    if length(kwargs) == 1
+        kwarg = only(kwargs) # only one kwarg is currently supported, TODO modify if we support more
+        key::Symbol, val = kwarg.args
+        key === :n_args || throw(ArgumentError("Unsupported keyword argument $key to `@functiondef`"))
+        (isa(val, Integer) && val > 0) || throw(ArgumentError("`n_args` keyword argument to `@functiondef` should be an integer > 0"))
+        f_n_args = val
     end
+
+    f = args[end]
+    f isa Symbol || throw(ArgumentError("Unsupported usage of `@functiondef`"))
+    f! = Symbol(f, :!)
+
+    return esc(_arg_expr(Val(f_n_args), f, f!))
 end
 
 """