@iftex
@finalout
@end iftex
-@comment $Id: scheme.texinfo,v 1.24 1993/10/14 06:42:03 cph Exp $
+@comment $Id: scheme.texinfo,v 1.25 1993/10/14 10:41:01 cph Exp $
@comment %**start of header (This is for running Texinfo on a region.)
@setfilename scheme
@settitle MIT Scheme Reference
@comment %**end of header (This is for running Texinfo on a region.)
@setchapternewpage odd
-@synindex vr fn
+@syncodeindex vr cp
+@syncodeindex fn cp
@comment Parts of this document are essentially plagiarized from "Common
@comment Lisp: The Language". Those parts are marked by the following
@titlepage
@title{MIT Scheme Reference Manual}
-@subtitle Edition 1.24 alpha
+@subtitle Edition 1.25 alpha
@subtitle for Scheme Release 7.2
@subtitle 14 October 1993
@author by Chris Hanson
* File-System Interface::
* Error System::
* Graphics::
-* Procedure Index:: Index of Procedures, Special Forms, and Variables
-* Concept Index:: Index of Concepts
+* Index::
--- The Detailed Node Listing ---
Many procedures signal an error when an argument is of the wrong type;
usually this error is a condition of type
@code{condition-type:wrong-type-argument}.
+@findex condition-type:wrong-type-argument
In addition to the standard data-type names (@var{pair}, @var{list},
@var{boolean}, @var{string}, etc.), the following names as arguments
@code{condition-type:unassigned-variable}; sometimes the compiler does
not generate code to signal the error. Unassigned variables are useful
only in combination with side effects (@pxref{Assignments}).
+@findex condition-type:unassigned-variable
@node Environment Concepts, Initial and Current Environments, Variable Bindings, Scheme Concepts
@subsection Environment Concepts
@cindex error, unbound variable (defn)
An @dfn{environment} is a set of variable bindings. If an environment
has no binding for a variable, that variable is said to be @dfn{unbound}
-in that environment. Referencing an unbound variable signals an
-``Unbound Variable'' error.
+in that environment. Referencing an unbound variable signals a
+condition of type @code{condition-type:unbound-variable}.
+@findex condition-type:unbound-variable
@cindex extension, of environment (defn)
@cindex environment, extension (defn)
@table @asis
@item Required
All of the @dfn{required} parameters are matched against the arguments
-first. If there are fewer arguments than required parameters, a ``Wrong
-Number of Arguments'' error is signalled; this error is also signalled
-if there are more arguments than required parameters and there are no
-further parameters.
+first. If there are fewer arguments than required parameters, an error
+of type @code{condition-type:wrong-number-of-arguments} is signalled;
+this error is also signalled if there are more arguments than required
+parameters and there are no further parameters.
@cindex required parameter (defn)
@cindex parameter, required (defn)
+@findex condition-type:wrong-number-of-arguments
@item Optional
Once the required parameters have all been matched, the @dfn{optional}
fewer arguments than optional parameters, the unmatched parameters are
bound to special objects called @dfn{default objects}. If there are
more arguments than optional parameters, and there are no further
-parameters, a ``Wrong Number of Arguments'' error is signalled.
+parameters, an error of type
+@code{condition-type:wrong-number-of-arguments} is signalled.
@cindex optional parameter (defn)
@cindex parameter, optional (defn)
@cindex default object (defn)
+@findex condition-type:wrong-number-of-arguments
@findex default-object?
The predicate @code{default-object?}, which is true only of default
MIT Scheme allows any of the @var{init}s to be omitted, in which
case the corresponding @var{variable}s are temporarily unassigned.
-An error is signalled if any of the @var{variable}s are unbound.
-However, because @code{fluid-let} operates by means of side effects, it
-is valid for any @var{variable} to be unassigned when the form is
-entered.
+An error of type @code{condition-type:unbound-variable} is signalled if
+any of the @var{variable}s are unbound. However, because
+@code{fluid-let} operates by means of side effects, it is valid for any
+@var{variable} to be unassigned when the form is entered.
+@findex condition-type:unbound-variable
Here is an example showing the difference between @code{fluid-let} and
@code{let}. First see how @code{let} affects the binding of a variable:
* Numerical operations::
* Numerical input and output::
* Fixnum and Flonum Operations::
+* Random Numbers::
@end menu
@node Numerical types, Exactness, , Numbers
numbers of mixed exactness, and the numerical value of the result cannot
be represented as an inexact number without loss of accuracy, then the
procedure may report a violation of an implementation
-restriction.@footnote{MIT Scheme signals an error in this case.}
+restriction.@footnote{MIT Scheme signals an error of type
+@code{condition-type:bad-range-argument} in this case.}
+@findex condition-type:bad-range-argument
@end deffn
@deffn procedure + z1 @dots{}
value returned is the inexact number that is numerically closest to the
argument. If an exact argument has no reasonably close inexact
equivalent, then a violation of an implementation restriction may be
-reported; MIT Scheme signals an error in this case.
+reported; MIT Scheme signals an error of type
+@code{condition-type:bad-range-argument} in this case.
+@findex condition-type:bad-range-argument
@code{inexact->exact} returns an exact representation of @var{z}. The
value returned is the exact number that is numerically closest to the
argument. If an inexact argument has no reasonably close exact
equivalent, then a violation of an implementation restriction may be
-reported; MIT Scheme signals an error in this case.
+reported; in MIT Scheme this case does not occur because all inexact
+numbers are representable as exact numbers.
These procedures implement the natural one-to-one correspondence between
exact and inexact integers throughout an implementation-dependent range.
allows for infinities, NaNs, and non-flonum representations.
@end deffn
+@defvr {variable+} flonum-unparser-cutoff
+This variable controls the action of @code{number->string} when
+@var{number} is a flonum (and consequently controls all printing of
+flonums). This variable can have the following values:
+
+@itemize @bullet
+@item
+The symbol @code{normal}, which is the initial value of this variable,
+causes flonums to be printed with full precision. @code{number->string}
+uses as many digits as are necessary to display all of the information
+in the flonum. This value may also be specified as a list @code{(normal
+@var{n})} where @var{n} is an exact integer; @var{n} is ignored.
+
+@item
+The list @code{(relative @var{n})}, where @var{n} is an exact positive
+integer, constrains @code{number->string} to represent the flonum using
+at most @var{n} significant digits. @code{number->string} rounds the
+result so that it is as accurate as possible. For example:
+
+@example
+@group
+(number->string (* 4 (atan 1 1)))
+ @result{} "3.141592653589793"
+(fluid-let ((flonum-unparser-cutoff '(relative 5)))
+ (number->string (* 4 (atan 1 1))))
+ @result{} "3.1416"
+@end group
+@end example
+
+@item
+The list @code{(absolute @var{n})}, where @var{n} is an exact integer,
+constrains @code{number->string} to represent the flonum by rounding it
+at the @var{n}th digit to the right of the decimal point; if @var{n} is
+negative, the number is rounded @code{(- @var{n})} digits to the left of
+the decimal point. For example:
+
+@example
+@group
+(fluid-let ((flonum-unparser-cutoff '(absolute 5)))
+ (number->string (* 4 (atan 1 1))))
+ @result{} "3.14159"
+(fluid-let ((flonum-unparser-cutoff '(absolute 5)))
+ (number->string (* 4000 (atan 1 1))))
+ @result{} "3141.59265"
+(fluid-let ((flonum-unparser-cutoff '(absolute -4)))
+ (number->string (* 4e10 (atan 1 1))))
+ @result{} "31415930000."
+(fluid-let ((flonum-unparser-cutoff '(absolute -5)))
+ (number->string (* 4e10 (atan 1 1))))
+ @result{} "31415900000."
+@end group
+@end example
+@end itemize
+
+@noindent
+If @code{flonum-unparser-cutoff} is bound to a value different from
+those described here, @code{number->string} issues a warning and acts as
+though it had been bound to @code{normal}.
+@end defvr
+
@deffn procedure string->number string [radix]
Returns a number of the maximally precise representation expressed by
the given @var{string}. @var{Radix} must be an exact integer, either 2,
@end example
@end deffn
-@node Fixnum and Flonum Operations, , Numerical input and output, Numbers
+@node Fixnum and Flonum Operations, Random Numbers, Numerical input and output, Numbers
@section Fixnum and Flonum Operations
This section describes numerical operations that are restricted forms of
compiled, it does not check the types of its arguments.
@end deffn
+@node Random Numbers, , Fixnum and Flonum Operations, Numbers
+@section Random Numbers
+@cindex random number
+@cindex pseudo-random number
+@cindex number, pseudo-random
+
+MIT Scheme provides a facility for generating pseudo-random numbers.
+The current implementation is a ``subtract-with-carry'' random-number
+generator, based on the algorithm from @cite{A New Class of Random
+Number Generators}, George Marsaglia and Arif Zaman, @cite{The Annals of
+Applied Probability}, Vol.@: 1, No.@: 3, 1991. At the time it was
+implemented, this was a good algorithm for general purposes, but the
+state of the art in random-number generation is constantly changing. If
+necessary, the implementation will be updated to use a new algorithm
+while retaining the same interface.
+
+The interface described here is essentially identical to that of Common
+Lisp.
+
+@deffn {procedure+} random modulus [state]
+@var{Modulus} must be a positive real number. @code{random} returns a
+pseudo-random number between zero (inclusive) and @var{modulus}
+(exclusive). The exactness of the returned number is the same as the
+exactness of @var{modulus}. Additionally, if @var{modulus} is an exact
+integer, the returned number will be also. Usually, @var{modulus} is
+either an exact integer or an inexact real; the current implementation
+has been tuned to make these two cases fast.
+
+If @var{state} is given and not @code{#f}, it must be a random-state
+object; otherwise, it defaults to the value of the variable
+@code{*random-state*}. This object is used to maintain the state of the
+pseudo-random-number generator and is altered as a side effect of the
+@code{random} procedure.
+@end deffn
+
+@defvr {variable+} *random-state*
+This variable holds a data structure, a random-state object, that
+encodes the internal state of the random-number generator that
+@code{random} uses by default. A call to @code{random} will perform a
+side effect on this data structure. This variable may be changed, using
+@code{set!} or @code{fluid-let}, to hold a new random-state object.
+@end defvr
+
+@deffn {procedure+} make-random-state [state]
+This procedure returns a new random-state object, suitable for use as
+the value of the variable @code{*random-state*}. If @var{state} is not
+given or @code{#f}, @code{make-random-state} returns a @emph{copy} of
+the current random-number state object (the value of the variable
+@code{*random-state*}). If @var{state} is a random-state object, a copy
+of that object is returned. If @var{state} is @code{#t}, then a new
+random-state object is returned that has been ``randomly'' initialized
+by some means (such as by a time-of-day clock).
+@end deffn
+
+@deffn {procedure+} random-state? object
+Returns @code{#t} if @var{object} is a random-state object, otherwise
+returns @code{#f}.
+@end deffn
+
@node Characters, Strings, Numbers, Top
@chapter Characters
@deffn {procedure+} name->char string
Converts a string that names a character into the character specified.
-If @var{string} does not name any character, signals an error.
+If @var{string} does not name any character, @code{name->char} signals
+an error.
@example
(name->char "a") @result{} #\a
@end deffn
@deffn {procedure+} char->ascii char
-Returns the @sc{ascii} code for @var{char}. An error is signalled if
-@var{char} doesn't have an @sc{ascii} representation.
+Returns the @sc{ascii} code for @var{char}. An error
+@code{condition-type:bad-range-argument} is signalled if @var{char}
+doesn't have an @sc{ascii} representation.
+@findex condition-type:bad-range-argument
@end deffn
@deffn {procedure+} ascii->char code
@deffnx {procedure+} eighth list
@deffnx {procedure+} ninth list
@deffnx {procedure+} tenth list
-Returns the specified element of @var{list}, signalling an error if
+Returns the specified element of @var{list}. It is an error if
@var{list} is not long enough to contain the specified element (for
example, if the argument to @code{seventh} is a list that contains only
six elements).
@deffn {procedure+} unsigned-integer->bit-string length integer
Both @var{length} and @var{integer} must be exact non-negative integers.
@var{Integer} is converted to a newly allocated bit string of
-@var{length} bits. Signals an error if @var{integer} is too large to be
-represented in @var{length} bits.
+@var{length} bits. Signals an error of type
+@code{condition-type:bad-range-argument} if @var{integer} is too large
+to be represented in @var{length} bits.
+@findex condition-type:bad-range-argument
@end deffn
@deffn {procedure+} signed-integer->bit-string length integer
@var{Length} must be an exact non-negative integer, and @var{integer}
may be any exact integer. Converts @var{integer} into a newly allocated
bit string of @var{length} bits, using two's complement encoding for
-negative numbers. Signals an error if @var{integer} is too large to be
-represented in @var{length} bits.
+negative numbers. Signals an error of type
+@code{condition-type:bad-range-argument} if @var{integer} is too large
+to be represented in @var{length} bits.
+@findex condition-type:bad-range-argument
@end deffn
@deffn {procedure+} bit-string->unsigned-integer bit-string
@code{unhash} takes an exact non-negative integer @var{k} and returns
the object associated with that integer. If there is no object
associated with @var{k}, or if the object previously associated with
-@var{k} has been reclaimed by the garbage collector, an error is
-signalled. In other words, if @code{hash} previously returned @var{k}
-for some object, and that object has not been reclaimed, it is the value
-of the call to @code{unhash}.
+@var{k} has been reclaimed by the garbage collector, an error of type
+@code{condition-type:bad-range-argument} is signalled. In other words,
+if @code{hash} previously returned @var{k} for some object, and that
+object has not been reclaimed, it is the value of the call to
+@code{unhash}.
+@findex condition-type:bad-range-argument
@end deffn
An object that is passed to @code{hash} as an argument is not protected
the test may be less restrictive than the effect of calling the
procedure. In other words, these procedures may indicate that the
procedure will accept a given number of arguments, but if you call the
-procedure it may signal an error. This is because these procedures
-examine the apparent arity of a procedure. For example, here is a
-procedure that appears to accept any number of arguments, but when
-called will signal an error if the number of arguments is not one:
+procedure it may signal a
+@code{condition-type:wrong-number-of-arguments} error. This is because
+these procedures examine the apparent arity of a procedure. For
+example, here is a procedure that appears to accept any number of
+arguments, but when called will signal an error if the number of
+arguments is not one:
+@findex condition-type:wrong-number-of-arguments
@example
(lambda arguments (apply car arguments))
@deffn {procedure+} environment-lookup environment symbol
@var{Symbol} must be bound in @var{environment} or one of its ancestor
-environments. Returns the value to which it is bound. Signals an error
-if @var{symbol} is unassigned.
+environments. Returns the value to which it is bound.
@end deffn
@deffn {procedure+} environment-assignable? environment symbol
These procedures check the type of @var{object}, signalling an error of
type @code{condition-type:wrong-type-argument} if it is not an input
port or output port, respectively. Otherwise they return @var{object}.
+@findex condition-type:wrong-type-argument
@end deffn
@deffn procedure current-input-port
@cindex construction, of file input port
Takes a filename referring to an existing file and returns an input port
capable of delivering characters from the file. If the file cannot be
-opened, an error is signalled.
+opened, an error of type @code{condition-type:file-operation-error} is
+signalled.
+@findex condition-type:file-operation-error
@end deffn
@deffn procedure open-output-file filename [append?]
@cindex construction, of file output port
Takes a filename referring to an output file to be created and returns
an output port capable of writing characters to a new file by that name.
-If the file cannot be opened, an error is signalled.
+If the file cannot be opened, an error of type
+@code{condition-type:file-operation-error} is signalled.
+@findex condition-type:file-operation-error
@cindex appending, to output file
If @var{append?} is given and not @code{#f}, the file is opened in
@cindex construction, of file input port
Takes a filename referring to an existing file and returns an @sc{i/o}
port capable of reading characters from and writing characters to the
-file. If the file cannot be opened, an error is signalled.
+file. If the file cannot be opened, an error of type
+@code{condition-type:file-operation-error} is signalled.
+@findex condition-type:file-operation-error
This procedure is often used to open special files. For example, under
unix this procedure can be used to open terminal device files, @sc{pty}
@deffnx procedure call-with-output-file filename procedure
These procedures call @var{procedure} with one argument: the port
obtained by opening the named file for input or output, respectively.
-If the file cannot be opened, an error is signalled. If @var{procedure}
-returns, then the port is closed automatically and the value yielded by
-@var{procedure} is returned. If @var{procedure} does not return, then
-the port will not be closed automatically unless it is reclaimed by the
-garbage collector.@footnote{Because Scheme's escape procedures have
-unlimited extent, it is possible to escape from the current continuation
-but later to escape back in. If implementations were permitted to close
-the port on any escape from the current continuation, then it would be
-impossible to write portable code using both
-@code{call-with-current-continuation} and @code{call-with-input-file} or
-@code{call-with-output-file}.}
+If the file cannot be opened, an error of type
+@code{condition-type:file-operation-error} is signalled. If
+@var{procedure} returns, then the port is closed automatically and the
+value yielded by @var{procedure} is returned. If @var{procedure} does
+not return, then the port will not be closed automatically unless it is
+reclaimed by the garbage collector.@footnote{Because Scheme's escape
+procedures have unlimited extent, it is possible to escape from the
+current continuation but later to escape back in. If implementations
+were permitted to close the port on any escape from the current
+continuation, then it would be impossible to write portable code using
+both @code{call-with-current-continuation} and
+@code{call-with-input-file} or @code{call-with-output-file}.}
@end deffn
@deffn {procedure+} call-with-binary-input-file filename procedure
@deffn {procedure+} system-library-pathname pathname
@cindex library, system pathname
Locates @var{pathname} in MIT Scheme's system library directory. An
-error is signalled if @var{pathname} cannot be located on the library
-search path.
+error of type @code{condition-type:file-operation-error} is signalled if
+@var{pathname} cannot be located on the library search path.
+@findex condition-type:file-operation-error
@example
@group
@node File Manipulation, Directory Reader, Working Directory, File-System Interface
@section File Manipulation
+This section describes procedures that manipulate files and directories.
+Any of these procedures can signal a number of errors for many reasons.
+The specifics of these errors are much too operating-system dependent to
+document them here. However, if such an error is signalled by one of
+these procedures, it will be of type
+@code{condition-type:file-operation-error}.
+@findex condition-type:file-operation-error
+
@deffn {procedure+} file-exists? filename
@cindex existence, testing of file
Returns @code{#t} if @var{filename} is an existing file or directory;
-otherwise returns @code{#f}. If the file is a symbolic link, this
-procedure tests the existence of the file linked to, not the link
-itself.
+otherwise returns @code{#f}. In operating systems that support symbolic
+links, if the file is a symbolic link, this procedure tests the
+existence of the file linked to, not the link itself.
@end deffn
@deffn {procedure+} copy-file source-filename target-filename
Deletes the file named @var{filename}.
@end deffn
-@deffn {procedure+} ->truename pathname
+@deffn {procedure+} ->truename filename
@cindex truename, of input file
This function attempts to discover and return the ``true name'' of the
-file associated with the @var{pathname} within the file system. An
-error is signalled if the appropriate file cannot be located within the
-file system.
+file associated with @var{filename} within the file system. An error of
+type @code{condition-type:file-operation-error} is signalled if the
+appropriate file cannot be located within the file system.
+@findex condition-type:file-operation-error
@end deffn
-@deffn {procedure+} file-modification-time filename
-@deffnx {procedure+} file-modification-time-direct filename
-@cindex modification time, of file
-Returns the modification time of @var{filename} as an exact integer.
-The result may be compared to other modification times using ordinary
-integer arithmetic. If @var{filename} names a file that does not exist,
-returns @code{#f}. If @var{filename} names a symbolic link,
-@code{file-modification-time-direct} returns the modification time of
-the link, while @code{file-modification-time} returns the modification
-time of the file linked to.
+@deffn {procedure+} call-with-temporary-filename procedure
+@code{call-with-temporary-filename} generates a temporary filename, and
+calls @var{procedure} with that filename as its sole argument. The
+filename is guaranteed not to refer to any existing file, and, barring
+unusual circumstances, it can be used to open an output file without
+error. When @var{procedure} returns, if the file referred to by the
+filename exists, it is deleted; then, the value yielded by
+@var{procedure} is returned. If @var{procedure} escapes from its
+continuation, and the file referred to by the filename exists, it is
+deleted.
@end deffn
@deffn {procedure+} file-directory? filename
@cindex directory, predicate for
Returns @code{#t} if the file named @var{filename} exists and is a
-directory. Otherwise returns @code{#f}. If @var{filename} names a
-symbolic link, this examines the file linked to, not the link itself.
+directory. Otherwise returns @code{#f}. In operating systems that
+support symbolic links, if @var{filename} names a symbolic link, this
+examines the file linked to, not the link itself.
@end deffn
@deffn {procedure+} file-symbolic-link? filename
@cindex symbolic link, predicate for
-If the file named @var{filename} exists and is a symbolic link, this
-procedure returns the contents of the symbolic link as a newly allocated
-string. The returned value is the name of the file that the symbolic
-link points to and must be interpreted relative to the directory of
-@var{filename}. If @var{filename} either does not exist or is not a
-symbolic link, this procedure returns @code{#f}.
+In operating systems that support symbolic links, if the file named
+@var{filename} exists and is a symbolic link, this procedure returns the
+contents of the symbolic link as a newly allocated string. The returned
+value is the name of the file that the symbolic link points to and must
+be interpreted relative to the directory of @var{filename}. If
+@var{filename} either does not exist or is not a symbolic link, or if
+the operating system does not support symbolic links, this procedure
+returns @code{#f}.
+@end deffn
+
+@deffn {procedure+} file-readable? filename
+Returns @code{#t} if @var{filename} names a file that can be opened for
+input; i.e.@: a @dfn{readable} file. Otherwise returns @code{#f}.
+@end deffn
+
+@deffn {procedure+} file-writable? filename
+Returns @code{#t} if @var{filename} names a file that can be opened for
+output; i.e.@: a @dfn{writable} file. Otherwise returns @code{#f}.
+@end deffn
+
+@deffn {procedure+} file-access filename mode
+@var{Mode} must be an exact integer between @code{0} and @code{7}
+inclusive; it is a bitwise-encoded predicate selector with @code{1}
+meaning ``executable'', @code{2} meaning ``writable'', and @code{4}
+meaning ``readable''. @code{file-access} returns @code{#t} if
+@var{filename} exists and satisfies the predicates selected by
+@var{mode}. For example, if @var{mode} is @code{5}, then @var{filename}
+must be both readable and executable. If @var{filename} doesn't exist,
+or if it does not satisfy the selected predicates, @code{#f} is
+returned.
+@end deffn
+
+@deffn {procedure+} file-modes filename
+If @var{filename} names an existing file, @code{file-modes} returns an
+exact non-negative integer encoding the file's permissions. The
+encoding of this integer is operating-system dependent, but typically it
+contains bits that indicate what users and processes are allowed to
+read, write, or execute the file. If @var{filename} does not name an
+existing file, @code{#f} is returned.
+@end deffn
+
+@deffn {procedure+} set-file-modes! filename modes
+@var{Filename} must name an existing file. @var{Modes} must be an exact
+non-negative integer that could have been returned by a call to
+@code{file-modes}. @code{set-file-modes!} modifies the file's
+permissions to be those encoded by @var{modes}.
+@end deffn
+
+@deffn {procedure+} file-modification-time filename
+@cindex modification time, of file
+Returns the modification time of @var{filename} as an exact integer.
+The result may be compared to other file times using ordinary integer
+arithmetic. If @var{filename} names a file that does not exist,
+@code{file-modification-time} returns @code{#f}.
+
+@findex file-modification-time-direct
+@findex file-modification-time-indirect
+In operating systems that support symbolic links, if @var{filename}
+names a symbolic link, @code{file-modification-time} returns the
+modification time of the file linked to. An alternate procedure,
+@code{file-modification-time-direct}, returns the modification time of
+the link itself; in all other respects it is identical to
+@code{file-modification-time}. For symmetry,
+@code{file-modification-time-indirect} is a synonym of
+@code{file-modification-time}.
+@end deffn
+
+@deffn {procedure+} file-access-time filename
+@cindex access time, of file
+Returns the access time of @var{filename} as an exact integer. The
+result may be compared to other file times using ordinary integer
+arithmetic. If @var{filename} names a file that does not exist,
+@code{file-access-time} returns @code{#f}.
+
+Some operating systems don't implement access times; in those systems
+@code{file-access-time} returns an unspecified value.
+
+@findex file-access-time-direct
+@findex file-access-time-indirect
+In operating systems that support symbolic links, if @var{filename}
+names a symbolic link, @code{file-access-time} returns the access time
+of the file linked to. An alternate procedure,
+@code{file-access-time-direct}, returns the access time of the link
+itself; in all other respects it is identical to
+@code{file-access-time}. For symmetry, @code{file-access-time-indirect}
+is a synonym of @code{file-access-time}.
+@end deffn
+
+@deffn {procedure+} set-file-times! filename access-time modification-time
+@var{Filename} must name an existing file, while @var{access-time} and
+@var{modification-time} must be valid file times that might have been
+returned by @code{file-access-time} and @code{file-modification-time},
+respectively. @code{set-file-times!} alters the access and modification
+times of the file specified by @var{filename} to the values given by
+@var{access-time} and @var{modification-time}, respectively. For
+convenience, either of the time arguments may be specified as @code{#f};
+in this case the corresponding time is not changed.
+@code{set-file-times!} returns an unspecified value.
@end deffn
@deffn {procedure+} file-attributes filename
@item
The inode number of the file, an exact non-negative integer.
@end enumerate
-@end deffn
+@findex file-attributes-direct
+@findex file-attributes-indirect
+In operating systems that support symbolic links, if @var{filename}
+names a symbolic link, @code{file-attributes} returns the attributes of
+the link itself. An alternate procedure,
+@code{file-attributes-indirect}, returns the attributes of the file
+linked to; in all other respects it is identical to
+@code{file-attributes}. For symmetry, @code{file-attributes-direct} is
+a synonym of @code{file-attributes}.
+@end deffn
@node Directory Reader, , File Manipulation, File-System Interface
@section Directory Reader
files.
@end defvr
-@node Graphics, Procedure Index, Error System, Top
+@node Graphics, Index, Error System, Top
@chapter Graphics
@cindex graphics
Overwrites any previously existing file of that name.
@end deffn
-@node Procedure Index, Concept Index, Graphics, Top
-@unnumbered Index of Procedures, Special Forms, and Variables
-@printindex fn
-
-@node Concept Index, , Procedure Index, Top
-@unnumbered Index of Concepts
+@node Index, , Graphics, Top
+@unnumbered Index
@printindex cp
@summarycontents
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