From f0a49aaf85a2ea8ae4b6dc23599e3d419dd22e54 Mon Sep 17 00:00:00 2001 From: wolf Date: Sat, 3 Sep 2005 01:25:34 +0000 Subject: [PATCH] Add a little bit of more documentation. git-svn-id: https://svn.dealii.org/trunk@11360 0785d39b-7218-0410-832d-ea1e28bc413d --- deal.II/examples/step-19/step-19.cc | 49 +++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/deal.II/examples/step-19/step-19.cc b/deal.II/examples/step-19/step-19.cc index 7aabec6c47..e20900bcd9 100644 --- a/deal.II/examples/step-19/step-19.cc +++ b/deal.II/examples/step-19/step-19.cc @@ -102,6 +102,55 @@ print_usage_message () // for, possibly, the output file name and // format, we nevertheless want to show how // to work with parameter files. + // + // In short, the ``ParameterHandler'' class + // works as follows: one declares the entries + // of parameters that can be given in input + // files together, and later on one can read + // an input file in which these parameters + // are set to their values. If a parameter is + // not listed in the input file, the default + // value specified in the declaration of that + // parameter is used. After that, the program + // can query the values assigned to certain + // parameters from the ``ParameterHandler'' + // object. + // + // Declaring parameters can be done using the + // ``ParameterHandler::declare_entry'' + // function. It's arguments are the name of a + // parameter, a default value (given as a + // string, even if the parameter is numeric + // in nature, and thirdly an object that + // describes constraints on values that may + // be passed to this parameter. In the + // example below, we use an object of type + // ``Patterns::Anything'' to denote that + // there are no constraints on file names + // (this is, of course, not true -- the + // operating system does have constraints, + // but from an application standpoint, almost + // all names are valid). In other cases, one + // may, for example, use + // ``Patterns::Integer'' to make sure that + // only parameters are accepted that can be + // interpreted as integer values (it is also + // possible to specify bounds for integer + // values, and all values outside this range + // are rejected), ``Patterns::Double'' for + // floating point values, classes that make + // sure that the given parameter value is a + // comma separated list of things, etc. Take + // a look at the ``Patterns'' namespace to + // see what is possible. + // + // The fourth argument to ``declare_entry'' + // is a help string that can be printed to + // document what this parameter is meant to + // be used for and other information you may + // consider important when declaring this + // parameter. The default value of this + // fourth argument is the empty string. void declare_parameters () { prm.declare_entry ("Output file", "", -- 2.39.5