#macro(store)#set($foo_ = $foo)#set($bar_ = $bar)#end##
#macro(reset)#set($foo = $foo_)#set($bar = $bar_)#end##
#macro(state)foo=$foo#end##

#macro(disp $foo)[foo=$foo]#end
#macro(setn $foo)#set($foo=$null)#disp($foo)#end
#macro(setv $foo)#if(!$foo)#set($foo='inn')#end#disp($foo)#end
#macro(sub)#set($foo='sub')#end

#macro(test)
1. missing argument
#store#state => disp miss #disp() => #state#reset
#store#state => setn miss #setn() => #state#reset
#store#state => setv miss #setv() => #state#reset
2. null argument
#store#state => disp null #disp($null) => #state#reset
#store#state => setn null #setn($null) => #state#reset
#store#state => setv null #setv($null) => #state#reset
3. non-colliding argument
#store#state => disp ncol #disp($bar) => #state#reset
#store#state => setn ncol #setn($bar) => #state#reset
#store#state => setv ncol #setv($bar) => #state#reset
4. colliding argument
#store#state => disp coll #disp($foo) => #state#reset
#store#state => setn coll #setn($foo) => #state#reset
#store#state => setv coll #setv($foo) => #state#reset
#end


A) Null Values
#set($foo = $null)
#set($bar = $null)
#test()

B) Non-null Values
#set($foo = 'foo')
#set($bar = 'bar')
#test()