87 lines
4.1 KiB
Text
87 lines
4.1 KiB
Text
% Copyright 2005-2017 Cisco Systems, Inc.
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%
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% Licensed under the Apache License, Version 2.0 (the "License");
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% you may not use this file except in compliance with the License.
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% You may obtain a copy of the License at
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%
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% http://www.apache.org/licenses/LICENSE-2.0
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%
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% Unless required by applicable law or agreed to in writing, software
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% distributed under the License is distributed on an "AS IS" BASIS,
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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% See the License for the specific language governing permissions and
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% limitations under the License.
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\chapter{Preface}
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{\ChezScheme} is both a general-purpose programming language and
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an implementation of that language, with supporting tools and
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documentation.
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As a superset of the language described in the Revised$^6$ Report
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on Scheme (R6RS), {\ChezScheme} supports all standard features of
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Scheme, including first-class procedures, proper treatment of tail
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calls, continuations, user-defined records, libraries, exceptions,
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and hygienic macro expansion.
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{\ChezScheme} supports numerous non-R6RS features.
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A few of these are local and top-level modules,
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local import, foreign datatypes and procedures, nonblocking I/O,
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an interactive top-level, compile-time values and properties,
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pretty-printing, and formatted output.
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The implementation includes a compiler that generates native code
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for each processor upon which it runs along with a run-time system
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that provides automatic storage management, foreign-language
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interfaces, source-level debugging, profiling support, and an
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extensive run-time library.
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The threaded versions of {\ChezScheme} support native threads, allowing
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Scheme programs to take advantage of multiprocessor or multiple-core
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systems.
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Nonthreaded versions are also available and are faster for
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single-threaded applications.
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Both 32-bit and 64-bit versions are available for some platforms.
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The 64-bit versions support larger heaps, while the 32-bit versions
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are faster for some applications.
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{\ChezScheme}'s interactive programming system includes an expression
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editor that, like many shells, supports command-line editing, a history
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mechanism, and command completion.
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Unlike most shells that support command-line editing, the expression
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editor properly supports multiline expressions.
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{\ChezScheme} is intended to be as reliable and efficient as possible,
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with reliability taking precedence over efficiency if necessary.
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Reliability means behaving as designed and documented.
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While a {\ChezScheme} program can always fail to work properly
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because of a bug in the program, it should never fail because of a
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bug in the {\ChezScheme} implementation.
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Efficiency means performing at a high level, consuming minimal CPU
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time and memory.
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Performance should be balanced across features, across run time and
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compile time, and across programs and data of different sizes.
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These principles guide {\ChezScheme} language and tool design as
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well as choice of implementation technique; for example, a language
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feature or debugging hook might not exist in {\ChezScheme} because
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its presence would reduce reliability, efficiency, or both.
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The compiler has been rewritten for Version~9 and generates
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substantially faster code than the earlier compiler at the cost of
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greater compile time.
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This is the primary difference between Versions~8 and~9.
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This book (CSUG) is a companion to \emph{The Scheme Programming
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Language, 4th Edition} (TSPL4).
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TSPL4 serves as an introduction to and reference for R6RS, while
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CSUG describes {\ChezScheme} features and tools that are not part
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of R6RS.
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For the reader's convenience, the summary of forms and index at the back
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of this book contain entries from both books, with each entry from TSPL4
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marked with a ``t'' in front of its page number.
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In the online version, the page numbers given in the summary of forms and
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index double as direct links into one of the documents or the other.
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Additional documentation for {\ChezScheme} includes release notes, a
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manual page, and a number of published papers and articles that describe
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various aspects of the system's design and implementation.
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Thank you for using {\ChezScheme}.
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