gistfile1.txt

* Modules have been added as a new program structure to improve
 encapsulation and sharing of code. Some existing and new
 identifiers have been factored out into separate modules.

* Exceptions can now be signalled explicitly with raise,
 raise-continuable or error, and can be handled with
 with-exception-handler and the guard syntax.

* New disjoint types supporting access to multiple fields can be
 generated with define-record-type.

* Parameter objects can be created with make-parameter, and
 dynamically rebound with parameterize.

* Blobs, homogeneous vectors of integers in the range [0..255],
 have been added as a new disjoint type.

* Ports can now be designated as binary or character ports, with
 new procedures for reading and writing binary data.

* String ports have been added as a way to write characters to
 and read characters from strings.

* Current-input-port and current-output-port are now parameter
 objects, along with the newly introduced current-error-port.

* Syntax-rules now recognizes as a wildcard, allows the ellipsis
 symbol to be specified explicitly instead of the default ...,
 allows template escapes with an ellipsis-prefixed list, and
 allows tail patterns to follow an ellipsis pattern.

* Syntax-error has been added as a way to signal immediate and
 more informative errors when a form is expanded.

* Internal define-syntax forms are now allowed preceding any
 internal defines.

* Letrec* has been added, and internal define specified in terms
 of it.

* Case now supports a => syntax analagous to cond.

* Case-lambda has been added to the base library as a way to
 dispatch on the number of arguments passed to a procedure.

* Positive and negative infinity and a NaN object have been added
 to the numeric tower as inexact values with the written
 representations +inf.0, -inf.0 and +nan.0, respectively.

* Map and for-each are now required to terminate on the shortest
 list when inputs have different length.

* Member and assoc now take an optional third argument for the
 equality predicate to use.

* Exact-integer? and exact-integer-sqrt have been added.

* Make-list, copy-list, list-set!, string-map, string-for-each,
 string->vector, copy-vector, vector-map, vector-for-each, and
 vector->string have been added to round out the sequence
 operations.

* The set of characters used is required to be consistent with
 the latest Unicode standard only in so far as the
 implementation supports Unicode.

* string-ni=? and related procedures have been added to compare
 strings as though they had gone through an
 implementation-defined normalization, without exposing the
 normalization.

* The case-folding behavior of the reader can now be explicitly
 controlled, with no folding as the default.

* The reader now recognizes the new comment syntax #; to skip the
 next datum, and allows nested block comments with #| ... |#.

* Data prefixed with reader labels #<n>= can be referenced with
 #<n># allowing for reading and writing of data with shared
 structure.

* Strings and symbols now allow mnemonic and numeric escape
 sequences, and the list of named characters has been extended.

* File-exists? and delete-file are available in the (scheme file)
 module.

* An interface to the system environment and command line is
 available in the (scheme process-context) module.

* Procedures for accessing the current time are available in
 the (scheme time) module.

* A complete set of integer division operators is available in
 the (scheme division) module.

* Transcript-on and transcript-off have been removed.