Reader

Like the scanner, the reader returns either an end-of-file delimiter or the actual object read. The end-of-file object is of type zodiac:eof, as defined in Section . All other values are elements of zodiac:read:

zodiac:read : zodiac (object)

The reader's output is sub-divided into scalar and sequence objects:

zodiacscalar : read ()

zodiac:sequence : read (length)

Most of these sub-types should be self-explanatory:

zodiac:string : scalar ()

zodiac:boolean : scalar ()

zodiac:number : scalar ()

zodiac:symbol : scalar (orig-name marks)

zodiac:char : scalar ()

zodiac:external : scalar ()

zodiac:list : sequence (marks)

zodiac:vector : sequence ()

zodiac:improper-list : sequence (period marks)

In the case of zodiac:scalar objects, the object field contains the Scheme representation of that object. All zodiac:sequence objects have a list of zodiac:read objects in their object field; in the case of zodiac:improper-list, the length of this list is one greater than the number of pairs that constitute the list.

The zodiac:external struct may contain any scheme value in the read field, except those listed in other structures. That is, it will not be a string, boolean, number, symbol or character, but it might be a procedure, the void value, or an instance of a class.

The period field contains a zodiac:period which gives the location of the period in the source that marks a list as being improper. The orig-name and marks fields are used by parsers that perform hygienic macro-expansion.

• Argument Lists