[ET Trac] [Einstein Toolkit] #1651: Problems with expansions in parameter files

[Einstein Toolkit]

#1651: Problems with expansions in parameter files
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  Reporter:  hinder  |       Owner:                     
      Type:  defect  |      Status:  new                
  Priority:  major   |   Milestone:                     
 Component:  Cactus  |     Version:  development version
Resolution:          |    Keywords:                     
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Comment (by rhaas):

 Technically the CoordBase::dy already has a value in the first line,
 namely the default value (which is 1). I am fine with making parameter
 files declarative rather than imperative. The required changes would seem
 to be:

 * have the parser check before using a variable value that it has been set
 (ie that the Parameter_NSet or whatever call returns >= 1)
 * forbid $a = 42 type assignments to happen more than once for the same
 variable (currently $a type assignments can be changed, see )

 The only legitimate use for order dependency would be something like this:

 {{{
 $default_dx = CoordBase::dx
 CoordBase::dx = 42
 foo::bar = $default_dx
 }}}

 or:

 {{{
 $foo = 12
 bar::baza[0] = $foo
 bar::bazb[0] = $foo
 $foo = 13
 bar::baza[1] = $foo
 bar::bazb[1] = $foo
 }}}

 ie to either safe the default value or to set up a set of similar stanzas.
 Both can be achieved without though by either spelling out the default
 from the param.ccl files or using more variables. I tend to think that the
 safety benefit of declarative parfiles outweights the usefulness of these
 corner cases.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/1651#comment:3>
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