I have just another question. On wiki in System macros/ Handling arguments (http://wiki.contextgarden.net/System_Macros/Handling_Arguments) are mentioned these macros:    

\dosingleargumentwithset \command[#1]
\dodoubleargumentwithset \command[#1][#2]
\dotripleargumentwithset \command[#1][#2][#3]
\dodoubleemptywithset    \command[#1][#2]
\dotripleemptywithset    \command[#1][#2][#3]

I'm not sure but I think, that I read somewhere that these are old and obsolete. Is true or these macros are still in use and I just mistook it?