KvpValue::Type::LIST and KvpFrame <-> SCM

[christopherlam]

• gncEntry precision bugs moved to gncEntry and invoice plugin page #1312
• creates a lispy kvp-frame representation
• avoids segfault when navigating non-existent frame:

  (let ((book (gnc-get-current-book)))
    (define (try path)
      (format #t "retrieve ~s ~s\n"
              path (qof-book-get-option book path)))
    (qof-book-set-option book "bla" '("top" "lvl1a"))
    (qof-book-set-option book "arg" '("top" "lvl1b"))
    (qof-book-set-option book "baf" '("top" "lvl1c" "lvl2" "lvl3"))
    (qof-book-set-option book '"baf" '("top" "lvl1c" "lvl2" "lvl3"))
    (qof-book-set-option book #("arg" "1" "2" 3) '("top" "lvl1d"))
    (qof-book-set-option book
                         '(("a" . "alpha")
                           ("b" . "beta")
                           ("c" . "charlie"))
                         '("top" "lvl1e"))
    (try '("top"))
    (try '("top" "lvl1a"))
    (try '("top" "lvl1b"))
    (try '("top" "lvl1c"))
    (try '("top" "lvl1c" "lvl2"))
    (try '("top" "lvl1c" "lvl2" "lvl3"))
    (try '("top" "lvl1c" "lvl2" "error"))
    (try '("top" "lvl1d"))
    (try '("top" "lvl1e"))
    (try '("top" "lvl1e" "a"))
    (try '("top" "error")))

outputs

retrieve ("top") (("lvl1a" . "bla") ("lvl1b" . "arg") ("lvl1c" ("lvl2" ("lvl3" . "baf"))) ("lvl1d" . #("arg" "1" "2" 3)) ("lvl1e" ("a" . "alpha") ("b" . "beta") ("c" . "charlie")))
retrieve ("top" "lvl1a") "bla"
retrieve ("top" "lvl1b") "arg"
retrieve ("top" "lvl1c") (("lvl2" ("lvl3" . "baf")))
retrieve ("top" "lvl1c" "lvl2") (("lvl3" . "baf"))
retrieve ("top" "lvl1c" "lvl2" "lvl3") "baf"
retrieve ("top" "lvl1c" "lvl2" "error") #f
retrieve ("top" "lvl1d") #("arg" "1" "2" 3)
retrieve ("top" "lvl1e") (("a" . "alpha") ("b" . "beta") ("c" . "charlie"))
retrieve ("top" "lvl1e" "a") "alpha"
retrieve ("top" "error") #f

[christopherlam]

• more capable kvp<->SCM conversion, can convert KvpFrame into a nested assoc-list
• can also convert KvpValue::Type:GLIST into an SCM vector

An alternate mapping would be: scheme hash table to/from KVP frames, and scheme lists to/from GNC_TYPE_LIST. The main disadvantage in this case is that hash tables are less readable in scheme. Otherwise it's a better mapping.

[christopherlam]

So we have two options:

• KvpFrame == SCM list-of-pairs; KvpValue::Type::GLIST == SCM list
• KvpFrame == SCM hash-table; KvpValue::Type::GLIST == SCM vector

There's potentially a third option which offers the readability of lists in guile:

• KvpFrame == SCM list-of-pairs; KvpValue::Type::GLIST == SCM list of non-pairs

This is possible because there's no direct mapping of SCM pair onto any KvpValue type. So, the scm_to_kvp_value_ptr test will be if (scm_is_list (val) && scm_is_true (scm_map (scm_c_eval_string ("pair?"), val))) convert into a KvpFrame.

[jralls]

Good start.