Re: default values

[etienne grossmann]

  Hello

From: address@hidden (Paul Kienzle)
#
#  I need a mechanism for defaulting the default values for variables.
#  For example, should the default frame_step on a spectrogram be 1ms,
#  5ms or 10ms?  Granted, the frame_step can be sent in as a parameter,
#  but in an interactive environment, it is better if the defaults have
#  the value the user usually wants.
# 
#  One way is to use:
# 
#      function myfunc(pa, pb)
#          global myfunc_pb = 37;
#          if nargin<2 || isempty(pb), pb=myfunc_pb; endif
#          ...
#      endfunction

  I usually do 

     function  myfunc(pa, pb)
       if exist("pb") != 1, pb = 37 ; end
       ...
     end

  Simple, no global variable is needed, but you can't change the
default from the command line ...

# 
#  This does exactly what I want, except that it leaves the definition
#  of myfunc_pb in the global symbol table.  Instead, I wrote a function
#  default.cc which takes the name of the global variable and a default
#  value, returning the value of the global if it is defined, otherwise
#  returning the default.  E.g.,
# 
#      function myfunc(pa, pb)
#          if nargin<2 || isempty(pb), pb=default("myfunc_pb",37); endif
#          ...
#      endfunction
# 
#  Is this something which should be part of the main distribution of
#  Octave?  Or should I just go ahead and pollute the global namespace
#  with default defaults?

  Cheers,

  Etienne

ps : The original post was on octave-source.



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