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Kawa: Compiling Scheme to Java

1.7 Collections

Kawa has a rudimentary hierarchy of collection classes.

class Sequence { abstract public int length(); abstract public Object elementAt (int index); ... }

A Sequence is the abstract class that includes lists, vectors, and strings.

class FString extends Sequence { char[] value; ... }

Used to implement fixed-length mutable strings (array of Unicode character). This is used to represent Scheme strings.

class FVector extends Sequence { Object[] value; ... }

Used to implement fixed-length mutable general one-dimensional array of Object. This is used to represent Scheme vectors.

class List extends Sequence { protected List () { } static public List Empty = new List (); ... }

Used to represent Scheme (linked) lists. The empty list '() is the static (global) value List.Empty. Non-empty-lists are implemented using Pair objects.

class Pair extends Sequence { public Object car; public Object cdr; ... }

Used for Scheme pairs.

class PairWithPosition extends Pair { ... }

Like Pair, but includes the filename and linenumber in the file from which the pair was read.

Future plans include more interesting collection classes, such a sequences implemented as a seekable disk file; lazily evaluated sequences; hash tables; APL-style multi-dimensional arrays; stretchy buffers.(1)