Teuchos_YAML.hpp File Reference

A TeuchosParser Language for a subset of YAML. More...

#include <Teuchos_Language.hpp>
#include <Teuchos_ReaderTables.hpp>

Go to the source code of this file.

Namespaces
	Teuchos
	The Teuchos namespace contains all of the classes, structs and enums used by Teuchos, as well as a number of utility routines.

Detailed Description

A TeuchosParser Language for a subset of YAML.

This is a grammar for a subset of the YAML language. Since YAML is indentation-sensitive, it is not context-free. An extension has been made to Teuchos::Reader to emit INDENT and DEDENT tokens in order to make indentation detectable by a context-free grammar.

Known limitations of this grammar compared to the full YAML language, in particular those which are relevant to Teuchos::ParameterList:

1. INDENT and DEDENT tokens must be matched, meaning the indentation of the YAML file itself must be nicely nested. Examples of valid YAML that this grammar cannot handle, and workarounds:

   # nested block sequences compressed onto one line:
   - - - one
       - two
       - three
     - ten
     - twenty
   - one hundred
   # do not compress the first line:
   -
     -
       - one
       - two
       - three
     - ten
     - twenty
   - one hundred

   # comments not indented the same as subsequent lines:
   all:
      one: 1
      two: 2
   #bad comment
      three: 3
   # indent the comments:
   all:
      one: 1
      two: 2
      #good comment
      three: 3

   # flow sequences and maps that span multiple lines
   timesteps: [1, 2, 3,
      4, 5]
   # keep it on one line, or use block sequences
   timesteps: [1, 2, 3, 4, 5]
   timesteps:
     - 1
     - 2
     - 3
     - 4
     - 5

   # block scalars with non-nested indentation
   inline file: |
      if (a == 5) {
         strange();
       indentation();
     }
   # ensure block scalars have nested indentation
   inline file: |
     if (a == 5) {
       strange();
       indentation();
     }

2. Scalars can start with a '.' or '-', but not two such symbols in a row

   # ".." at the beginning of a scalar
   filepath: ../cube.exo
   # quote the scalar
   filepath: "../cube.exo"

Definition in file Teuchos_YAML.hpp.