@cindex language, PSPP
@cindex PSPP, language
-@quotation
-@strong{Please note:} PSPP is not even close to completion.
-Only a few statistical procedures are implemented. PSPP
-is a work in progress.
-@end quotation
-
This chapter discusses elements common to many PSPP commands.
Later chapters will describe individual commands in detail.
* Types of Commands:: Commands come in several flavors.
* Order of Commands:: Commands combine to form syntax files.
* Missing Observations:: Handling missing observations.
-* Variables:: The unit of data storage.
+* Datasets:: Data organization.
* Files:: Files used by PSPP.
* File Handles:: How files are named.
* BNF:: How command syntax is described.
significant inside strings.
Strings can be concatenated using @samp{+}, so that @samp{"a" + 'b' +
-'c'} is equivalent to @samp{'abc'}. Concatenation is useful for
-splitting a single string across multiple source lines. The maximum
-length of a string, after concatenation, is 255 characters.
-
-Strings may also be expressed as hexadecimal, octal, or binary
-character values by prefixing the initial quote character by @samp{X},
-@samp{O}, or @samp{B} or their lowercase equivalents. Each pair,
-triplet, or octet of characters, according to the radix, is
-transformed into a single character with the given value. If there is
-an incomplete group of characters, the missing final digits are
-assumed to be @samp{0}. These forms of strings are nonportable
-because numeric values are associated with different characters by
-different operating systems. Therefore, their use should be confined
-to syntax files that will not be widely distributed.
-
-@cindex characters, reserved
-@cindex 0
-@cindex white space
-The character with value 00 is reserved for
-internal use by PSPP. Its use in strings causes an error and
-replacement by a space character.
+'c'} is equivalent to @samp{'abc'}. So that a long string may be
+broken across lines, a line break may precede or follow, or both
+precede and follow, the @samp{+}. (However, an entirely blank line
+preceding or following the @samp{+} is interpreted as ending the
+current command.)
+
+Strings may also be expressed as hexadecimal character values by
+prefixing the initial quote character by @samp{x} or @samp{X}.
+Regardless of the syntax file or active dataset's encoding, the
+hexadecimal digits in the string are interpreted as Unicode characters
+in UTF-8 encoding.
+
+Individual Unicode code points may also be expressed by specifying the
+hexadecimal code point number in single or double quotes preceded by
+@samp{u} or @samp{U}. For example, Unicode code point U+1D11E, the
+musical G clef character, could be expressed as @code{U'1D11E'}.
+Invalid Unicode code points (above U+10FFFF or in between U+D800 and
+U+DFFF) are not allowed.
+
+When strings are concatenated with @samp{+}, each segment's prefix is
+considered individually. For example, @code{'The G clef symbol is:' +
+u"1d11e" + "."} inserts a G clef symbol in the middle of an otherwise
+plain text string.
@item Punctuators and Operators
@cindex punctuators
When it is the last non-space character on a line, a period is not
treated as part of another token, even if it would otherwise be part
of, e.g.@:, an identifier or a floating-point number.
-
-Actually, the character that ends a command can be changed with
-@cmd{SET}'s ENDCMD subcommand (@pxref{SET}), but we do not recommend
-doing so. Throughout the remainder of this manual we will assume that
-the default setting is in effect.
@end table
@node Commands
There are multiple ways to mark the end of a command. The most common
way is to end the last line of the command with a period (@samp{.}) as
described in the previous section (@pxref{Tokens}). A blank line, or
-one that consists only of white space or comments, also ends a command
-by default, although you can use the NULLINE subcommand of @cmd{SET}
-to disable this feature (@pxref{SET}).
+one that consists only of white space or comments, also ends a command.
@node Syntax Variants
-@section Variants of syntax.
+@section Syntax Variants
@cindex Batch syntax
@cindex Interactive syntax
-There are two variants of command syntax, @i{viz}: @dfn{batch} mode and
-@dfn{interactive} mode.
-Batch mode is the default when reading commands from a file.
-Interactive mode is the default when commands are typed at a prompt
-by a user.
-Certain commands, such as @cmd{INSERT} (@pxref{INSERT}), may explicitly
-change the syntax mode.
-
-In batch mode, any line that contains a non-space character
-in the leftmost column begins a new command.
-Thus, each command consists of a flush-left line followed by any
-number of lines indented from the left margin.
-In this mode, a plus or minus sign (@samp{+}, @samp{@minus{}}) as the
-first character in a line is ignored and causes that line to begin a
-new command, which allows for visual indentation of a command without
-that command being considered part of the previous command.
-The period terminating the end of a command is optional but recommended.
-
-In interactive mode, each command must either be terminated with a period,
-or an empty line must follow the command.
-The use of (@samp{+} and @samp{@minus{}} as continuation characters is not
-permitted.
+There are three variants of command syntax, which vary only in how
+they detect the end of one command and the start of the next.
+
+In @dfn{interactive mode}, which is the default for syntax typed at a
+command prompt, a period as the last non-blank character on a line
+ends a command. A blank line also ends a command.
+
+In @dfn{batch mode}, an end-of-line period or a blank line also ends a
+command. Additionally, it treats any line that has a non-blank
+character in the leftmost column as beginning a new command. Thus, in
+batch mode the second and subsequent lines in a command must be
+indented.
+
+Regardless of the syntax mode, a plus sign, minus sign, or period in
+the leftmost column of a line is ignored and causes that line to begin
+a new command. This is most useful in batch mode, in which the first
+line of a new command could not otherwise be indented, but it is
+accepted regardless of syntax mode.
+
+The default mode for reading commands from a file is @dfn{auto mode}.
+It is the same as batch mode, except that a line with a non-blank in
+the leftmost column only starts a new command if that line begins with
+the name of a PSPP command. This correctly interprets most valid PSPP
+syntax files regardless of the syntax mode for which they are
+intended.
+
+The @option{--interactive} (or @option{-i}) or @option{--batch} (or
+@option{-b}) options set the syntax mode for files listed on the PSPP
+command line. @xref{Main Options}, for more details.
@node Types of Commands
@section Types of Commands
Analyze data, writing results of analyses to the listing file. Cause
transformations specified earlier in the file to be performed. In a
more general sense, a @dfn{procedure} is any command that causes the
-active file (the data) to be read.
+active dataset (the data) to be read.
@end table
@node Order of Commands
When executed in the initial or procedure state, causes a transition to
the transformation state.
@item
-Clears the active file if executed in the procedure or transformation
+Clears the active dataset if executed in the procedure or transformation
state.
@end itemize
@item
Causes a transition to the INPUT PROGRAM state.
@item
-Clears the active file.
+Clears the active dataset.
@end itemize
@item @cmd{FILE TYPE}
@item
Causes a transition to the FILE TYPE state.
@item
-Clears the active file.
+Clears the active dataset.
@end itemize
@item Other file definition commands
@item
Cause a transition to the transformation state.
@item
-Clear the active file, except for @cmd{ADD FILES}, @cmd{MATCH FILES},
+Clear the active dataset, except for @cmd{ADD FILES}, @cmd{MATCH FILES},
and @cmd{UPDATE}.
@end itemize
Variables, whether numeric or string, can have designated
@dfn{user-missing values}. Every user-missing value is an actual value
for that variable. However, most of the time user-missing values are
-treated in the same way as the system-missing value. String variables
-that are wider than a certain width, usually 8 characters (depending on
-computer architecture), cannot have user-missing values.
+treated in the same way as the system-missing value.
For more information on missing values, see the following sections:
-@ref{Variables}, @ref{MISSING VALUES}, @ref{Expressions}. See also the
+@ref{Datasets}, @ref{MISSING VALUES}, @ref{Expressions}. See also the
documentation on individual procedures for information on how they
handle missing values.
-@node Variables
-@section Variables
-@cindex variables
+@node Datasets
+@section Datasets
+@cindex dataset
+@cindex variable
@cindex dictionary
-Variables are the basic unit of data storage in PSPP. All the
-variables in a file taken together, apart from any associated data, are
-said to form a @dfn{dictionary}.
-Some details of variables are described in the sections below.
+PSPP works with data organized into @dfn{datasets}. A dataset
+consists of a set of @dfn{variables}, which taken together are said to
+form a @dfn{dictionary}, and one or more @dfn{cases}, each of which
+has one value for each variable.
+
+At any given time PSPP has exactly one distinguished dataset, called
+the @dfn{active dataset}. Most PSPP commands work only with the
+active dataset. In addition to the active dataset, PSPP also supports
+any number of additional open datasets. The @cmd{DATASET} commands
+can choose a new active dataset from among those that are open, as
+well as create and destroy datasets (@pxref{DATASET}).
+
+The sections below describe variables in more detail.
@menu
* Attributes:: Attributes of variables.
@item Width
(string variables only) String variables with a width of 8 characters or
fewer are called @dfn{short string variables}. Short string variables
-can be used in many procedures where @dfn{long string variables} (those
+may be used in a few contexts where @dfn{long string variables} (those
with widths greater than 8) are not allowed.
-Certain systems may consider strings longer than 8
-characters to be short strings. Eight characters represents a minimum
-figure for the maximum length of a short string.
-
@item Position
Variables in the dictionary are arranged in a specific order.
@cmd{DISPLAY} can be used to show this order: see @ref{DISPLAY}.
@cindex @code{$TIME}
@item $TIME
-Number of seconds between midnight 14 Oct 1582 and the time the active file
+Number of seconds between midnight 14 Oct 1582 and the time the active dataset
was read, in format F20.
@cindex @code{$WIDTH}
contains an ordinary decimal number, a time or date, a number in binary
or hexadecimal notation, or one of several other notations. Input
formats are used by commands such as @cmd{DATA LIST} that read data or
-syntax files into the PSPP active file.
+syntax files into the PSPP active dataset.
Every input format corresponds to a default @dfn{output format} that
specifies the formatting used when the value is output later. It is
The maximum width for time and date formats is 40 columns. Minimum
input and output width for each of the time and date formats is shown
below:
+
@float
@multitable {DATETIME} {Min. Input Width} {Min. Output Width} {4-digit year}
@headitem Format @tab Min. Input Width @tab Min. Output Width @tab Option
@cindex scratch variables
Most of the time, variables don't retain their values between cases.
-Instead, either they're being read from a data file or the active file,
+Instead, either they're being read from a data file or the active dataset,
in which case they assume the value read, or, if created with
@cmd{COMPUTE} or
another transformation, they're initialized to the system-missing value
statistical procedures. The output files may be in any number of formats,
depending on how PSPP is configured.
-@cindex active file
-@cindex file, active
-@item active file
-The active file is the ``file'' on which all PSPP procedures are
-performed. The active file consists of a dictionary and a set of cases.
-The active file is not necessarily a disk file: it is stored in memory
-if there is room.
-
@cindex system file
@cindex file, system
@item system file
Portable files are files in a text-based format that store a dictionary
and a set of cases. @cmd{IMPORT} and @cmd{EXPORT} read and write
portable files.
-
-@cindex scratch file
-@cindex file, scratch
-@item scratch file
-Scratch files consist of a dictionary and cases and may be stored in
-memory or on disk. Most procedures that act on a system file or
-portable file can use a scratch file instead. The contents of scratch
-files persist within a single PSPP session only. @cmd{GET} and
-@cmd{SAVE} can be used to read and write scratch files. Scratch files
-are a PSPP extension.
@end table
@node File Handles
@section File Handles
@cindex file handles
-A @dfn{file handle} is a reference to a data file, system file, portable
-file, or scratch file. Most often, a file handle is specified as the
+A @dfn{file handle} is a reference to a data file, system file, or
+portable file. Most often, a file handle is specified as the
name of a file as a string, that is, enclosed within @samp{'} or
@samp{"}.
also required to read data files in binary formats. @xref{FILE HANDLE},
for more information.
-PSPP assumes that a file handle name that begins with @samp{#} refers to
-a scratch file, unless the name has already been declared on @cmd{FILE
-HANDLE} to refer to another kind of file. A scratch file is similar to
-a system file, except that it persists only for the duration of a given
-PSPP session. Most commands that read or write a system or portable
-file, such as @cmd{GET} and @cmd{SAVE}, also accept scratch file
-handles. Scratch file handles may also be declared explicitly with
-@cmd{FILE HANDLE}. Scratch files are a PSPP extension.
-
In some circumstances, PSPP must distinguish whether a file handle
refers to a system file or a portable file. When this is necessary to
read a file, e.g.@: as an input file for @cmd{GET} or @cmd{MATCH FILES},
The file to which a file handle refers may be reassigned on a later
@cmd{FILE HANDLE} command if it is first closed using @cmd{CLOSE FILE
-HANDLE}. The @cmd{CLOSE FILE HANDLE} command is also useful to free the
-storage associated with a scratch file. @xref{CLOSE FILE HANDLE}, for
+HANDLE}. @xref{CLOSE FILE HANDLE}, for
more information.
@node BNF
@dfn{start symbol}. The start symbol defines the entire syntax for
that command.
@end itemize
-@setfilename ignored