mv_package

mapfield

MAPFIELD — the portable %MAP% spec builder. A mapping says how a document's fields become MultiValue attributes; MAPFIELD builds one field of that spec, and spec-driven codecs (json, and later yaml/xml) consume it to turn Pick dynamic arrays into structured data and back.

SPEC<-1> = MAPFIELD(name, attr, conv, type, assoc)

builds name<VM>attr<VM>conv<VM>type<VM>assoc:

• attr — the MV attribute the field lands at.
• type — TEXT/NUMERIC/DATE/TIME; derived from conv when empty

(MD/MR/ML → NUMERIC, MT → TIME, D… → DATE, else TEXT).

• assoc — empty = a single-valued (scalar) field; else the association name,

whose members decode as parallel multivalues (an array of objects).

mvx vs udt

On mvx, MAPFIELD is a compiler builtin — this package is udt-only (systems: udt). A consumer that compiles on both selects with a directive:

$IFDEF MVX
   * MAPFIELD is the compiler builtin — nothing to declare
$ELSE
   DEFFUN MAPFIELD(A, B, C, D, E)   ; * this package's cataloged function
$ENDIF

Pure BASIC — installs by cataloging BP/MAPFIELD (no native build).

Consumers

json depends on mapfield (on udt); a yaml or xml package would too — one shared projection layer, one parser each.