I still wonder about the complexity of all this for decimal. We now have two grammars on top of each other, this being the actual one for decimal:

  http://speleotrove.com/decimal/daconvs.html


For string conversions I'd prefer a lax way (similar to OCaml) that would somehow be specified in terms of preprocessing, same as the leading/trailing whitespace removal. Short of "ignore all underscores" it isn't easy though.