+
@node Conditionals and Looping
@chapter Conditional and Looping Constructs
@cindex conditionals
@cindex flow of control
@cindex control flow
-This chapter documents PSPP commands used for conditional execution,
+This chapter documents @pspp{} commands used for conditional execution,
looping, and flow of control.
@menu
var_list
num_or_range@dots{}
'string'@dots{}
+ ALL
num_or_range takes one of the following forms:
number
different variables, numbers, or strings into the block with each
repetition.
-Specify a dummy variable name followed by an equals sign (@samp{=}) and
-the list of replacements. Replacements can be a list of variables
-(which may be existing variables or new variables or some combination),
-numbers, or strings. When new variable names are
-specified, @cmd{DO REPEAT} creates them as numeric variables. When numbers
-are specified, runs of increasing integers may be indicated as
-@code{@var{num1} TO @var{num2}}, so that
+Specify a dummy variable name followed by an equals sign (@samp{=})
+and the list of replacements. Replacements can be a list of existing
+or new variables, numbers, strings, or @code{ALL} to specify all
+existing variables. When numbers are specified, runs of increasing
+integers may be indicated as @code{@var{num1} TO @var{num2}}, so that
@samp{1 TO 5} is short for @samp{1 2 3 4 5}.
Multiple dummy variables can be specified. Each
for each dummy variable is substituted; and so on.
Dummy variable substitutions work like macros. They take place
-anywhere in a line that the dummy variable name occurs as a token,
-including command and subcommand names. For this reason,
-words commonly used in command and subcommand names should not be used
-as dummy variable identifiers.
-
-If PRINT is specified on @cmd{END REPEAT}, the commands after substitutions
+anywhere in a line that the dummy variable name occurs. This includes
+command and subcommand names, so command and subcommand names that
+appear in the code block should not be used as dummy variable
+identifiers. Dummy variable substitutions do not occur inside quoted
+strings, comments, unquoted strings (such as the text on the
+@cmd{TITLE} or @cmd{DOCUMENT} command), or inside @cmd{BEGIN
+DATA}@dots{}@cmd{END DATA}.
+
+New variable names used as replacements are not automatically created
+as variables, but only if used in the code block in a context that
+would create them, e.g.@: on a @cmd{NUMERIC} or @cmd{STRING} command
+or on the left side of a @cmd{COMPUTE} assignment.
+
+Any command may appear within @subcmd{DO REPEAT}, including nested @subcmd{DO REPEAT}
+commands. If @cmd{INCLUDE} or @cmd{INSERT} appears within @subcmd{DO REPEAT},
+the substitutions do not apply to the included file.
+
+If @subcmd{PRINT} is specified on @cmd{END REPEAT}, the commands after substitutions
are made are printed to the listing file, prefixed by a plus sign
(@samp{+}).
@vindex LOOP
@display
-LOOP [index_var=start TO end [BY incr]] [IF condition].
+LOOP [@var{index_var}=@var{start} TO @var{end} [BY @var{incr}]] [IF @var{condition}].
@dots{}
-END LOOP [IF condition].
+END LOOP [IF @var{condition}].
@end display
@cmd{LOOP} iterates a group of commands. A number of
termination options are offered.
Specify index_var to make that variable count from one value to
-another by a particular increment. index_var must be a pre-existing
-numeric variable. start, end, and incr are numeric expressions
+another by a particular increment. @var{index_var} must be a pre-existing
+numeric variable. @var{start}, @var{end}, and @var{incr} are numeric expressions
(@pxref{Expressions}.)
-During the first iteration, index_var is set to the value of start.
-During each successive iteration, index_var is increased by the value of
-incr. If end > start, then the loop terminates when index_var > end;
-otherwise it terminates when index_var < end. If incr is not specified
+During the first iteration, @var{index_var} is set to the value of @var{start}.
+During each successive iteration, @var{index_var} is increased by the value of
+@var{incr}. If @var{end} > @var{start}, then the loop terminates
+when @var{index_var} > @var{end};
+otherwise it terminates when @var{index_var} < @var{end}. If @var{incr} is not specified
then it defaults to +1 or -1 as appropriate.
-If end > start and incr < 0, or if end < start and incr > 0, then the
-loop is never executed. index_var is nevertheless set to the value of
+If @var{end} > @var{start} and @var{incr} < 0, or if @var{end} < @var{start} and
+ @var{incr} > 0, then the
+loop is never executed. @var{index_var} is nevertheless set to the value of
start.
-Modifying index_var within the loop is allowed, but it has no effect on
-the value of index_var in the next iteration.
+Modifying @var{index_var} within the loop is allowed, but it has no effect on
+the value of @var{index_var} in the next iteration.
Specify a boolean expression for the condition on @cmd{LOOP} to
cause the loop to be executed only if the condition is true. If the
condition on @cmd{END LOOP} will always execute at least once.
If neither the index clause nor either condition clause is
-present, then the loop is executed MXLOOPS (@pxref{SET}) times.
+present, then the loop is executed @var{max_loops} (@pxref{SET}) times.
+The default value of @var{max_loops} is 40.
@cmd{BREAK} also terminates @cmd{LOOP} execution (@pxref{BREAK}).
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