06oct2020

I want to have a language where '//' is a token - integer division.
I want three options in scanner:
 1/ parse the comment and report it as a token
 2/ parse the comment and don't report it as a token (i.e. 'ignored')
 3/ don't parse it, report as TK_mark

This could apply separately for "#" and "//" and "/*".  But I only have two
type: TK_comment and TK_line_comment.

I could list these as 'known' but that prevents "///" being recognised
as a mark.

12mar2021
How to split values from type so they can be small - only one type
 pointer for an array, for example.
Currently a "value" contains both a 'type' and a union of options:
   str, num, bool, label, array(recursive), structure
where some of these include type information.

To split this I need to keep type and attach it to a var and pass
around with a value.  So that value needs to be a pointer to a union?
And a size in bytes?

17mar2021
 I need to have transient values - registers? - for holding the
 intermediate result of a computation before assigning to a variable.
 This is/was 'struct lrval' which was a val and a *lval.
 Now that a 'struct value' is always a pointer, the 'struct value' can be
 either the rval or lval, but I need to be able to store
 content as well - the old 'struct value val'.
 Maybe I want 'struct value' to still contain the thing (not a pointer)
 and use 'char  ptr[1]' for generic content.

10oct2021
 arrays can have a 'const' as the size - and they can be calculated
 from the current value of variables.  So how do we allocate them?
 In particular, how do we handle them appearing in recursive functions?

 For variables with a fixed size - known at function-start at least -
 we can allocate a stack frame for all of them, and the index off
 the stack frame.
 I guess var-sized arrays have a pointer in the stack frame, are
 allocated when they come into scope, and freed when they go out.

 So I need var-alloc for these to be quite different to other vars
 All vars need to be initialized when they come into scope, and
 de-initialized.

 Currently we initialise or re-initialised when entering scope,
 and only free when exiting program