Returns the number of members contained in this Item, if this Item is
a Record; otherwise returns 0 if this Item is not a Record.
Converts this Item into a boolean value, if possible; otherwise returns
undefined if this Item can't be converted into a boolean value.
Converts this Item into a boolean value, if possible; otherwise returns
orElse if this Item can't be converted into a boolean value.
Returns the sole member of this Item, if this Item is a Record
with exactly one member, and its member is a Value; returns Extant
if this Item is an empty Record; returns Absent if this Item is
a Field; otherwise returns this if this Item is a Record with more
than one member, or if this Item is a non-Record Value.
Used to convert a unary Record into its member Value. Facilitates
writing code that treats a unary Record equivalently to a bare Value.
Returns the value of the first member of this Item, if this Item is a
Record, and its first member is an Attr whose key string is
equal to tag; otherwise returns Absent if this Item is not a
Record, or if this Item is a Record whose first member is not an
Attr, or if this Item is a Record whose first member is an Attr
whose key does not equal the tag.
Used to conditionally get the value of the head Attr of a structure, if
and only if the key string of the head Attr is equal to the tag. Can
be used to check if a structure might conform to a nominal type named
tag, while simultaneously getting the value of the tag attribute.
Returns the unflattened header of
this Item, if this Item is a Record, and its first member is an
Attr whose key string is equal to tag; otherwise returns
undefined.
The headers of the tag attribute of a structure are like the
attributes of an XML element tag; through unlike an XML element, tag
attribute headers are not limited to string keys and values.
Returns true if this Item always evaluates to the
same Item.
Returns true if this Item is not Absent.
Converts this Item into a number value, if possible; otherwise returns
undefined if this Item can't be converted into a number value.
Converts this Item into a number value, if possible; otherwise returns
orElse if this Item can't be converted into a number value.
Converts this Item into a string value, if possible; otherwise returns
undefined if this Item can't be converted into a string value.
Converts this Item into a string value, if possible; otherwise returns
orElse if this Item can't be converted into a string value.
Returns the key string of the first member of this Item, if this Item
is a Record, and its first member is an Attr; otherwise returns
undefined if this Item is not a Record, or if this Item is a
Record whose first member is not an Attr.
Used to concisely get the name of the discriminating attribute of a
structure. The tag can be used to discern the nominal type of a
polymorphic structure, similar to an XML element tag.
Returns the flattened members of this Item after all
attributes have been removed, if this Item is a Record; otherwise
returns this if this Item is a non-Record Value, or returns
the value component if this Item is a Field.
Used to concisely get the scalar value of an attributed structure. An
attributed structure is a Record with one or more attributes that modify
one or more other members.
Returns the value component of this Item, if this Item is a Field;
otherwise returns this if this Item is aValue`.
Returns the heterogeneous sort order of this Item. Used to impose a
total order on the set of all items. When comparing two items of
different types, the items order according to their typeOrder}.
Returns the key component of this
Item, if thisItem is a <a href="_swim_structure.field.html">Field</a>; otherwise returns <a href="_swim_structure.absent.html">Absent</a> if thisItemis aValue`.