Module default_lua 

The value a Lua member takes when the stream does not carry it.

Table 9 of DDS-XTypes 1.3, as Lua. crate::default_python is the same table as Python and carries the clause quotations; this is a further derivation and deliberately not a call into any sibling — the columns are compared against each other, and a shared helper would make them agree about a mistake.

The Lua spellings, where they differ from every sibling

An aggregate is a table constructor, not a call. A Lua table needs no class and no constructor: { x = 0, y = 0.0 } is the value, member defaults nested inside. A nested aggregate member is still a call — ZD.zd_def_Inner() — so one type has one answer and two positions cannot drift.

An @optional member is a key left out. §7.2.2.4.4.4.8’s “Implementations shall not provide a default value” is the absence, and in Lua the absence of a value is the absence of the key; a constructor entry holding nil would not even create one.

A char and a wchar are the code point, as an integer. The member holds an integer — adapter/lua.rs’s mapping — so Table 9’s zero is 0, not a one-character string.

A long double is the decimal text "0.0". A Lua float is a binary64; the member holds text and runtime/lua converts exactly. "0.0" and not "0", because it is also what float128.bits_to_decimal answers for the zero pattern, and one value should have one spelling on both directions.

An enumeration’s default is read out of the descriptor. M.a.b.Colour.values.RED — the materialiser’s own table, through CodecTarget::enumerator_constant, so the file that declared the value is the file this reads it from.

A fixed array is that many entries, spelled out. A Lua table constructor evaluates each entry, so { ZD.zd_def_T(), ZD.zd_def_T() } is two distinct tables — there is no [x] * n aliasing trap to avoid, and the spelled-out form is simply the only form.

Functions

default_into

place = ZD.zd_def_<T>().

defaulter_from_decoder

The defaulter that goes with a decoder, by name: the two schemes differ in one word because both are built from the same key.

defaulter_name

The defaulter function name for a type — keyed like crate::emit::decode::decoder_name, by the IDL kind for a primitive: ten of the fifteen are one Lua integer and a name built from the holder would give them one defaulter.

lua_defaulters_called_by

The defaulters decls call, and exactly those, read off the emitted calls rather than derived a second time from the model — the same closure discipline default_python and default_c state at length.

lua_defaulters_over

Build the defaulter for each of types, once per name.

member_default

One member’s default: its @default, or its type’s. §7.2.2.4.4.4.9 puts the explicit one first.