Synopsis

typedef enum {
  NB_TYPE_INTEGER,
  NB_TYPE_FLOAT,
  NB_TYPE_COMPLEX,
  NB_TYPE_QUATERNION,
  NB_TYPE_STRING,
  NB_TYPE_ARRAY,
  NB_TYPE_PROC,
  NB_TYPE_OBJECT,
  NB_TYPE_REF,
  NB_TYPE_DEFER,
  NB_TYPE_MATRIX,
  NB_TYPE_PROGRAM,
  NB_TYPE_FREE,
  NB_TYPE_SENTINEL
} nb_cell_type_t;

Integer, float, and reference objects take one cell and can be held on the evaluation stack. Other objects (array, string, and program) are only held in memory and can span multiple object cells. Free cells are set to NB_TYPE_FREE so that the garbage collector can skip over them.

The ordering of these is specific in that the four language-level types that the user sees come first so that dispatching of operators based on type can be done by indexing a table of function pointers.

NB_TYPE_INTEGER

A 32-bit signed integer.

NB_TYPE_FLOAT

A 32-bit floating point value.

NB_TYPE_COMPLEX

A complex number spanning two cells.

NB_TYPE_QUATERNION

A quaternion spanning four cells.

NB_TYPE_STRING

A multi-cell string value.

NB_TYPE_ARRAY

A multi-cell array value.

NB_TYPE_PROC

A procedure. This isn't directly accessible.

NB_TYPE_OBJECT

An object. This isn't directly accessible.

NB_TYPE_REF

A reference to string, array, complex, or quaternion.

NB_TYPE_DEFER

A deferred expression.

NB_TYPE_MATRIX

A two-dimensional array of real values. This type is internal, has a short life, and and is not exposed to the user.

NB_TYPE_PROGRAM

The application program stored in object array. There is exactly one of these over the whole object array.

NB_TYPE_FREE

An unused run of cells in the heap.

NB_TYPE_SENTINEL

The sentinel marker. There is exactly one sentinel cell, the last cell of the memory array, with index NB_SENTINEL_INDEX. This cell marks the end of the cell array.