As of revision 784, literal constant substitution is implemented in the repository. This only works for literal expressions that evaluate to constants, such as "1" or "1.0" or "8675903". There is a trivial example in models/passing/ConstantSubstitution.R replicated here in its entirety:

require(OpenMx) fooThe next step will be to implement free parameter and fixed parameter substitution (this week), and then I can finish with global variable substitution in algebra expressions (either this week or next week).