How_can_I_obtain_the_value_of_a_MeqParm_for_use_in_my_MeqTree_script?

I would like to be able to write a script containing something like

ns.parm << ....

if Meq.Abs(ns.parm) > 0:
   do this
else:
   do that

Here the parm has a single value which is constant over time and frequency.

Does MeqTrees let me do something like the above?

Answer from Sarod: Here is a little utility function that will do what you want:

#
# utility to extract the default parms (if any) of a given MeqParm
# node. It will return the following in the given order, if they
# exist.
# 1. default_value
# 2. First coefficient of init_funklet
# 3. First coefficient of funklet
# 4. 0.0
def get_default_parms(nd):
 # get initrec
 irec=nd.initrec()
 #print irec
 # try to get default_value
 if irec.has_key('default_value'):
  cf=irec['default_value']
  # this need to be a scalar
  if cf.nelements()>=1:
     #my_val=cf.tolist().pop(0)
     my_val=numarray.ravel(cf)[0]
  else: #scalar
     my_val=float(cf)
 elif irec.has_key('init_funklet'):
  # get coeff array (or scalar)
  fn=irec['init_funklet']
  if(is_meqpolc(fn)):
   cf=fn['coeff']
   if cf.nelements()>=1:
     my_val=numarray.ravel(cf)[0]
   else: #scalar
     my_val=float(cf)
  elif(is_meqpolclog(fn)):
   cf=fn['coeff']
   if cf.nelements()>=1:
     my_val=numarray.ravel(cf)[0]
   else: #scalar
     my_val=float(cf)
   # return exponent
   my_val=math.pow(10,my_val)
  else: # error
   print "WARNING: unable to find a value for funklet",fn
   my_val=-1
 else: # error
   my_val=-1
 return my_val

You can use it like

value =  get_default_parms(ns.parm)
if value > 0:
  etc

NOTE: According to Oleg, this solution will only work for compile-time values: you get out what you put in there to begin with. A new node needs to be developed for run-time decision making.