- Rationale:
- The information necessary for applying exponents to a number is more
explicitly represented in the inputs to `fromRawNumber` than in the outputs
- This way, `exponentp` may simply return an `Int`
- Purpose: to reduce the verbosity of the previous implementation
- Split off `AmbiguousNumber` into its own type
- Introduce a function `AmbiguousNumber -> RawNumber` explicitly capturing the
disambiguation logic
- Reduce the number of remaining constructors in `RawNumber` to just two,
`WithSeparator` and `NoSeparator`
- The choice to distinguish by the presence of digit separators is motivated
by the need for this information later on when disallowing exponents on
numbers with digit separators
- Extracts the handling of signs out of `fromRawNumber` and into `signp` itself
- Rationale: The sign can be applied independently from the logic in
`fromRawNumber`
A commodity directive that doesn't specify the decimal point character
increases ambiguity and the chance of misparsing numbers, especially
as it overrides all style information inferred from the journal amounts.
In some cases it caused amounts with a decimal point to be parsed as if
with a digit group separator so 1.234 became 1234.
We could augment it with extra info from the journal amounts, when available,
but it would still be possible to be ambiguous, and that won't be obvious.
A commodity directive is what we recommend to nail down the style.
It seems the simple and really only way to do this reliably is to require
an explicit decimal point character. Most folks probably do this already.
Unfortunately, it makes another potential incompatiblity with ledger and
beancount journals. But the error message will be clear and easy to
work around.
