66 lines
2.6 KiB
ReStructuredText
66 lines
2.6 KiB
ReStructuredText
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.. highlight:: yaml
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=====================================================
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Differences between D:YAML and the YAML specification
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=====================================================
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There are some differences between D:YAML and the YAML 1.1 specification. Some
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are caused by difficulty of implementation of some features, such as multiple
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Unicode encodings within single stream, and some by unnecessary restrictions or
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ambiguities in the specification.
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Still, D:YAML tries to be as close to the specification as possible. D:YAML should
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never load documents with different meaning than according to the specification,
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and documents that fail to load should be very rare (for instance, very few
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files use multiple Unicode encodings).
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--------------------------
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List of known differences:
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--------------------------
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Differences that can cause valid YAML documents not to load:
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* At the moment, all mappings in the internal representation are ordered,
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and a comparison for equality between equal mappings with differing order
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will return false. This will be fixed once Phobos has a usable map type or
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D associative arrays work with variants.
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* No support for byte order marks and multiple Unicode encodings in a stream.
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* Plain scalars in flow context cannot contain ``,``, ``:`` and ``?``.
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This might change with ``:`` in the future.
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See http://pyyaml.org/wiki/YAMLColonInFlowContext for details.
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* The specification does not restrict characters for anchors and
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aliases. This may lead to problems, for instance, the document::
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[ *alias, value ]
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can be interpteted in two ways, as::
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[ "value" ]
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and::
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[ *alias , "value" ]
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Therefore we restrict aliases and anchors to ASCII alphanumeric characters.
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* The specification is confusing about tabs in plain scalars. We don't use tabs
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in plain scalars at all.
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* There is no support for recursive data structures in DYAML.
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Other differences:
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* Indentation is ignored in the flow context, which is less restrictive than the
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specification. This allows code such as::
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key: {
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}
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* Indentation rules for quoted scalars are loosed: They don't need to adhere
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indentation as ``"`` and ``'`` clearly mark the beginning and the end of them.
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* We allow ``_`` in tag handles.
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* Right now, two mappings with the same contents but different orderings are
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considered unequal, even if they are unordered mappings. This is because all
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mappings are ordered in the D:YAML implementation. This should change in
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future, once D associative arrays work with variant types or a map class or
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struct appears in Phobos.
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