Bundles the optional original text of a value with an optional in-memory form of it. More...
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Bundles the optional original text of a value with an optional in-memory form of it.
ILNode objects that do not represent literals will have a Value property that returns NoValue.Value. Also, the TextValue and TypeMarker for a value may not be known, in which case they will return an empty string and null, respectively. It could also be that the ISerializedLiteral.TextValue is known but the value it represents is not known, in which case the Value may be a copy of the TextValue.
If this object represents a literal, Value should never be NoValue.Value, and it should not be null unless null is the actual value of the literal.
In all, a literal may have the the following valid combinations of properties:
- TextValue.IsNull, null TypeMarker, valid Value: this combination often occurs when nodes created programmatically and have never been in text form before, but it may also occur if the parser isn't designed to preserve input text, or if the syntax is nonstandard and there is no benefit in preserving the text. Keep in mind that the TypeMarker dictates constraints on syntax, not just type, so if a language uses an unusual literal syntax the most reasonable thing is often to parse the text and not include it in the Loyc tree.
- TextValue.IsNull, non-null TypeMarker, valid Value: this combination can be used to disambiguate when one type corresponds to multiple TypeMarkers. For example, the literal 123 has the generic numeric type marker "_". This may be stored as a 32-bit integer in the Loyc tree, but suppose that an attempt is made to store the integer in an 8-bit integer variable. Should it succeed? It is conceivable that in a particular programming language, a generic number 123 (type marker "_") can be stored in a byte variable, but that a literal with the explicit type marker "_i32" should not be convertible to a byte because is marked as 32 bits.
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Non-null TextValue, non-null TypeMarker: In this case the Value will either be a parsed form of TextValue (so that
!Value.Equals(TextValue)or a boxed form of TextValue so thatValue.Equals(TextValue). The latter case indicates that the parser did not recognize the TypeMarker, or that parsing the TextValue failed, that literal parsing is not enabled in the parser, or that the value is a string but the parser chose not to convert it to the .NET native string type.
Caution: TextValue is UString and an "empty" UString is "equal" to a "null" UString since the list of characters is the same. Do not compare UString with null; instead, use UString.IsNull.
Additional Inherited Members | |
 Properties inherited from Loyc.Syntax.IUninterpretedLiteral | |
| UString | TextValue [get] |
| Represents the serialized text of the value. More... | |
| Symbol | TypeMarker [get] |
| Represents the type of the value. More... | |
| Properties inherited from Loyc.IHasValue< object > | |
| T | Value [get] |
