@ifinfo
This file documents the MIT Scheme system.
-Copyright @copyright{} 1988, 1989, 1990, 1991 Massachusetts Institute of Technology
+Copyright @copyright{} 1988-92 Massachusetts Institute of Technology
This material was developed by the Scheme project at the Massachusetts
Institute of Technology, Department of Electrical Engineering and Computer
@titlepage
@title{MIT Scheme Reference Manual}
-@subtitle Edition 1.1
+@subtitle Edition 1.2 alpha
@subtitle for Scheme Release 7.1.3
-@subtitle November 1991
+@subtitle July 1992
@author by Chris Hanson
@author the MIT Scheme Team
@author and a cast of thousands
@page
@vskip 0pt plus 1filll
-Copyright @copyright{} 1988, 1989, 1990, 1991 Massachusetts Institute of Technology
+Copyright @copyright{} 1988-92 Massachusetts Institute of Technology
This material was developed by the Scheme project at the Massachusetts
Institute of Technology, Department of Electrical Engineering and Computer
@end ifinfo
@menu
+* Acknowledgements:: Acknowledgements
* Overview:: Overview
* Special Forms:: Special Forms
* Equivalence Predicates:: Equivalence Predicates
* Custom Graphics Operations:: Custom Graphics Operations
* X Graphics:: X Graphics
* Starbase Graphics:: Starbase Graphics
+* Pictures:: Pictures (MIT 6.001 implementation only)
X Graphics
* X Graphics Type:: X Graphics Type
* Utilities for X Graphics:: Utilities for X Graphics
* Custom Operations on X Graphics Devices:: Custom Operations on X Graphics Devices
+
+Pictures (MIT 6.001 implementation only)
+
+* Construction of Pictures:: Construction of Pictures
+* Manipulating Pictures:: Manipulating Pictures
+* Displaying Pictures:: Displaying Pictures
+* Saving and Restoring Pictures:: Saving and Restoring Pictures
@end menu
@node Acknowledgements, Overview, Top, Top
@end deffn
@deffn {procedure+} stream-car stream
+@deffnx {procedure+} stream-first stream
@findex car
@findex head
Returns the first element in @var{stream}. @code{stream-car} is
equivalent to @code{car}.@footnote{@code{head}, a synonym for
@code{stream-car}, is provided for compatibility with old code; use
-@code{stream-car} in new code.}
+@code{stream-car} in new code.} @code{stream-first} is a synonym for
+@code{stream-car}.
@end deffn
@deffn {procedure+} stream-cdr stream
+@deffnx {procedure+} stream-rest stream
@findex force
@findex cdr
@findex tail
Returns the first tail of @var{stream}. Equivalent to @code{(force
(cdr @var{stream}))}.@footnote{@code{tail}, a synonym for
@code{stream-cdr}, is provided for compatibility with old code; use
-@code{stream-cdr} in new code.}
+@code{stream-cdr} in new code.} @code{stream-rest} is a synonym for
+@code{stream-cdr}.
@end deffn
@deffn {procedure+} stream-null? stream
* Clipping of Graphics Output:: Clipping of Graphics Output
* Custom Graphics Operations:: Custom Graphics Operations
* X Graphics:: X Graphics
-* Pictures:: Pictures (MIT 6.001 implementation only)
* Starbase Graphics:: Starbase Graphics
+* Pictures:: Pictures (MIT 6.001 implementation only)
@end menu
@node Opening and Closing of Graphics Devices, Coordinates for Graphics, Graphics, Graphics
the documentation for its type.
@end deffn
-@node X Graphics, Pictures, Custom Graphics Operations, Graphics
+@node X Graphics, Starbase Graphics, Custom Graphics Operations, Graphics
@section X Graphics
@cindex X graphics
in documentation of the @code{XLoadQueryFont} Xlib call.
@end deffn
-@node Pictures, Starbase Graphics, X Graphics, Graphics
-@section Pictures (MIT 6.001 implementation only)
-
-@cindex pictures
-A `picture' data object is a two-dimensional array of floating point
-numbers that represents a grey-scale image on the screen. The grey
-level that the value of each element represents is determined relative
-to the range of values of the array.
-
-The width of a picture is the number of elements in each row and the height is
-the number of elements in each column. The elements are referenced by giving
-the horizontal component first and the vertical one second, with the origin at
-the bottom left corner of the displayed picture.
-
-Coordinates (i,j) are "valid coordinates" of picture p if and only if:
-
- i,j are both exact integers and
- 0 <= i < (picture-width p) and 0 <= j < (picture-height p)
-
-@subsection Construction of Pictures
-
-@findex make-picture
-@deffn {procedure+} make-picture X Y [K]
- Returns a picture of width X and height Y. If K is specified then each
- picture element is initialized to K, otherwise the value of each is
- unspecified. X and Y must be exact integers and K must be real (if
- specified).
-@end deffn
-
-@findex procedure->picture
-@deffn {procedure+} procedure->picture X Y F
- F must be a real-valued function of two variables.
- Returns a picture of width X and height Y, such that the value of each
- element is the value of F at its indices, in floating point notation.
-
-@example
-@group
-(picture-ref (procedure->picture width height f) i j)
-@result{} (exact->inexact (f i j)) for all valid coordinates (i,j)
-@end group
-@end example
-@end deffn
-
-@cindex pgm-file
-@findex pgm-file->picture
-@deffn {procedure+} pgm-file->picture FILENAME
- Converts a grey-scale image stored in pgm format into a picture whose
- graphical representation will closely resemble that of the saved image.
-@end deffn
-
-@subsection Selecting Picture Components
-
-@findex picture?
-@deffn {procedure+} picture? OBJECT
- Returns `#t' if OBJECT is a picture, otherwise returns `#f'. Note that
- this means that the type-descriptor for OBJECT must be `eq?' to that of
- the picture-type for this procedure to return `#t'.
-@end deffn
-
-@findex picture-width
-@findex picture-height
-@deffn {procedure+} picture-width PICTURE
-@deffnx {procedure+} picture-height PICTURE
- These procedures return the width and height, respectively, of PICTURE.
-@end deffn
-
-@findex picture-min
-@findex picture-max
-@deffn {procedure+} picture-min PICTURE
-@deffnx {procedure+} picture-max PICTURE
- These procedures return the least and the greatest values stored in
- PICTURE.
-@end deffn
-
-@findex picture-ref
-@deffn {procedure+} picture-ref PICTURE I J
- Returns the value of element (I,J) of PICTURE (always a floating point
- number). I and J must both be valid coordinates of PICTURE.
-@end deffn
-
-@findex picture-set!
-@deffn {procedure+} picture-set! PICTURE I J K
- Stores K at element (I,J) in PICTURE and returns an unspecified value.
- K must be a real number and I and J must be valid coordinates of PICTURE.
-@end deffn
-
-@subsection Picture Operations
-
-@findex picture-map
-@deffn {procedure+} picture-map F PICTURE ...
- F must be an n-ary function where n is the number of PICTURE arguments
- passed to picture-map, and each PICTURE argument must have the same
- dimensions. Returns a newly allocated picture with each element containing
- the value of F applied to the list of corresponding elements of the
- PICTURE arguments.
-
- i.e. (picture-ref (picture-map f p1 p2 ... ) i j)
- => (f (picture-ref p1 i j) (picture-ref p2 i j) ... ).
-@end deffn
-
-@subsection Displaying and Saving Pictures
-
- To display pictures, a scheme graphics window must first be created.
- Although, any scheme window may be used, the colormap will not be
- guaranteed to be correct for grey-scale pictures, therefore the
- recommended way of creating windows for displaying pictures is to use the
- MAKE-WINDOW procedure.
-
-@findex picture-display
-@deffn {procedure+} picture-display W PICTURE [MIN [MAX]]
- Displays, in the window W, the largest integer scaling of PICTURE that
- can be contained in W. If MIN and MAX are specified then the grey levels
- will be computed using these values as PICTURE's minimum and maximum
- values, otherwise the actual least and greatest values of PICTURE will be
- used. The value returned by this procedure is unspecified.
-@end deffn
-
-@cindex pgm-file
-@findex picture->pgm-file
-@deffn {procedure+} picture->pgm-file PICTURE FILENAME
- Saves the contents of PICTURE in a file in the current directory with the
- name FILENAME. The PICTURE is written in pgm format. If FILENAME
- already exists, then it will be lost after evaluating this procedure.
-@end deffn
-
-@subsection Windows for Pictures
-
-@findex make-window
-@deffn {procedure+} make-window W H X Y
- Returns a scheme graphics device of width W, height H and screen-position
- X,Y (as would be given in an X geometry string) with a grey scale colormap
- attached.
-@end deffn
-
-@node Starbase Graphics, , Pictures, Graphics
+@node Starbase Graphics, Pictures, X Graphics, Graphics
@section Starbase Graphics
@cindex starbase graphics
They have no effect on text drawn prior to their invocation.
@end defop
+@node Pictures, , Starbase Graphics, Graphics
+@section Pictures (MIT 6.001 implementation only)
+
+@cindex pictures
+A @dfn{picture} data object is a two-dimensional array of real numbers
+that represents a grey-scale image on the screen. The grey level that
+the value of each element represents is determined relative to the range
+of values of the array.
+
+The width of a picture is the number of elements in each row and the
+height is the number of elements in each column. The elements are
+referenced by giving the horizontal component first and the vertical one
+second, with the origin at the bottom left corner of the displayed
+picture.
+
+Coordinates (@var{i},@var{j}) are @dfn{valid coordinates} of picture
+@var{p} if and only if:
+
+@example
+@group
+(and (exact-nonnegative-integer? @var{i})
+ (exact-nonnegative-integer? @var{j})
+ (< @var{i} (picture-width @var{p}))
+ (< @var{j} (picture-height @var{p})))
+@end group
+@end example
+
+@menu
+* Construction of Pictures:: Construction of Pictures
+* Manipulating Pictures:: Manipulating Pictures
+* Displaying Pictures:: Displaying Pictures
+* Saving and Restoring Pictures:: Saving and Restoring Pictures
+@end menu
+
+@node Construction of Pictures, Manipulating Pictures, Pictures, Pictures
+@subsection Construction of Pictures
+
+@code{make-picture} and @code{procedure->picture} are simple ways to
+make pictures. @code{picture-map} is a way to create a new picture by
+applying a procedure to one or more pictures. Pictures can also be made
+by reading files: see @code{pgm-file->picture}.
+
+@deffn {procedure+} make-picture x y [k]
+@var{X} and @var{y} must be exact positive integers and @var{k}, if
+specified, must be a real number. Returns a picture of width @var{x}
+and height @var{y}. If @var{k} is specified then each picture element
+is initialized to @var{k}, otherwise the elements are unspecified.
+@end deffn
+
+@deffn {procedure+} procedure->picture x y f
+@var{X} and @var{y} must be exact positive integers, and @var{f} must be
+a real-valued procedure of two variables. Returns a picture of width
+@var{x} and height @var{y}, where the value of each element is the
+result of applying @var{f} to the element's coordinates.
+@end deffn
+
+@deffn {procedure+} picture-map f picture @dots{}
+@var{F} must be a procedure, and each @var{picture} argument must have
+the same dimensions. Returns a newly allocated picture, each element of
+which is obtained by calling @var{f}, passing it as arguments the
+corresponding element of each @var{picture} argument. (Thus @var{f}
+must accept the same number of arguments as there are @var{picture}
+arguments to @code{picture-map}.)
+
+In other words, each element could have been initialized as follows:
+
+@example
+@group
+(picture-set! @var{result} @var{i} @var{j}
+ (@var{f} (picture-ref @var{picture} @var{i} @var{j}) @dots{}))
+@end group
+@end example
+@end deffn
+
+@node Manipulating Pictures, Displaying Pictures, Construction of Pictures, Pictures
+@subsection Manipulating Pictures
+
+@deffn {procedure+} picture? object
+Returns @code{#t} if @var{object} is a picture, otherwise returns
+@code{#f}.
+@end deffn
+
+@deffn {procedure+} picture-width picture
+@deffnx {procedure+} picture-height picture
+These procedures return the width and height, respectively, of
+@var{picture}.
+@end deffn
+
+@deffn {procedure+} picture-min picture
+@deffnx {procedure+} picture-max picture
+These procedures return, respectively, the least and the greatest values
+stored in @var{picture}.
+@end deffn
+
+@deffn {procedure+} picture-ref picture i j
+Returns the value of element (@var{i},@var{j}) of @var{picture} (always
+a real number). @var{I} and @var{j} must be valid coordinates for
+@var{picture}.
+@end deffn
+
+@deffn {procedure+} picture-set! picture i j k
+Stores @var{k} at element (@var{i},@var{j}) in @var{picture} and returns
+an unspecified value. @var{K} must be a real number and @var{I} and
+@var{j} must be valid coordinates for @var{picture}.
+@end deffn
+
+@node Displaying Pictures, Saving and Restoring Pictures, Manipulating Pictures, Pictures
+@subsection Displaying Pictures
+
+To display pictures, a scheme graphics window must first be created.
+Although, any scheme window may be used, the colormap will not be
+guaranteed to be correct for grey-scale pictures, therefore the
+recommended way of creating windows for displaying pictures is to use
+the @code{make-window} procedure.
+
+@deffn {procedure+} picture-display w picture [min [max]]
+Displays, in the window @var{w}, the largest integer scaling of
+@var{picture} that can be contained in @var{w}. If @var{min} and
+@var{max} are specified then the grey levels will be computed using
+these values as @var{picture}'s minimum and maximum values, otherwise
+the actual least and greatest values of @var{picture} will be used. The
+value returned by this procedure is unspecified.
+@end deffn
+
+@deffn {procedure+} make-window w h x y
+Returns a scheme graphics device of width @var{w}, height @var{h} and
+screen position @var{x},@var{y} (as would be given in an X geometry
+string) with a grey-scale colormap attached.
+@end deffn
+
+@node Saving and Restoring Pictures, , Displaying Pictures, Pictures
+@subsection Saving and Restoring Pictures
+
+Pictures can be read from or written to files in @sc{pgm} format using
+the following procedures.
+
+@deffn {procedure+} pgm-file->picture pathname
+Reads a grey-scale image stored in @sc{pgm} format from the file
+@var{pathname}, returning a picture whose graphical representation will
+closely resemble that of the saved image.
+@end deffn
+
+@deffn {procedure+} picture->pgm-file picture pathname
+Saves @var{picture} in @sc{pgm} format in the file @var{pathname}.
+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
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