At least with a push-parser, by the time the parser has figured out it
has an identifier, the lexer has forgotten the token, thus the annoying
and uninformative "undefined identifier " error messages. Since
identifiers should always have a value (and functions need a function
type), setting up a dummy symbol with just the identifier name
duplicated seems to do the trick. It is a bit wasteful of memory if
there are a lot of such errors between cmem resets, though.
The prefix gives more context to the error messages, making the system a
lot easier to use (it was especially helpful when getting my cvar revamp
into shape).
cexpr's symbol tables currently aren't readily extended, and dynamic
scoping is usually a good thing anyway. The chain of contexts is walked
when a symbol is not found in the current context's symtab, but minor
efforts are made to avoid checking the same symtab twice (usually cased
by cloning a context but not updating the symtab).
The generated short names for a lot of Vulkan enums start with a number
(eg VK_IMAGE_TYPE_2D -> 2d). Having to prefix the short name with ` is a
tiny cost for the convenience.
It is capable of parsing single expressions with fairly simple
operations. It current supports ints, enums, cvars and (external) data
structs. It is also thread-safe (in theory, needs proper testing) and
the memory it uses can be mass-freed.
