The C code int setCallback(Fl_Widget* wgt, Fl_Callback *cb, void *pdata=NULL, int num=1); Run
can be translated into proc setCallback*(wgt: ptr Fl_Widget; cb: ptr Fl_Callback; pdata: pointer = nil; num: cint = 1): cint Run Instead of setCallback(wgt, cb, nil, 2) Run I want to call the function as setCallback(wgt, cb, 0, 2) Run I have tried use converter toNil(x: int=0): type(nil) = nil Run but Error: invalid type: 'nil' in this context: 'proc (x: int): nil' for proc Run so, is it possible to write a convertor which actually convert number zero only to nil? thanks