Default

When a variable name is given without class or with a [F]class, a default priority order determines the class used for the variable. Default is used to define this search priority:

• For the tables classes when [F] is used.
• For all the classes when no class is given.

Default is also used in the syntax of a Case alternative (When Default). See Case for this syntax.

Syntax

CODECODE CODE 
  Default File CLASS
  Default CLASS_LIST
  Default CLASS
  Default Local
  Default Global

• CLASS is a class such as [V], [L], [abv], or [F:abv], where abv is the abbreviation of a table.
• CLASS_LIST is a list of at least two classes separated by commas.

Description and comments

The command Default defines the sequence in which the engine searches variables when their class is not specified, with the various syntax given below:

The syntax Default File is used to specify the default table. This table is used by default:

• When using Read, For, Look, Readlock, Write, Delete, Rewrite, Update, RewriteByKey, and DeleteByKey without specifying the table concerned.
• When using a variable with class [F] or [G], it searches first in the default table. If it is not found in this file, it then searches in the other tables.

The syntax Default class specifies the variable class to use by default when a variable is not preceded by any class indicator. If the variable cannot be found in the default class, it searches in the other classes.

The syntax Default CLASSES_LIST gives a complete list of classes (there must be at least two) for the search on variables when no class is specified. From the time a list of classes is given, only those in the list are used to search for variables.

Warning: if class [S] is excluded from this list, there is no access to the engine system variables such as fstat unless they are preceded by [S].

The two syntaxes, Default Local and Default Global, define the class used to create default variables. Remember that variables can be created automatically by a routine, a procedure, or a menu during allocation. If the variable to which a value is assigned has no class, and if it does not exist, then it is created automatically with a type matching that of the assigned expression, selected from Date, Decimal and Char, and with maximum length. The class in which the variable is created is therefore a [V] if using Default Global and [L] if using Default Local.

Examples

   # Only the following classes are accessible for a variable
   # whose class is not specified, and in the order given           
     Default [S], [L], [V], [C], [F:ATB]
   # By default, variables without class are searched for in class [L]
     Default [L]
   # By default, non-existent variables are created in class [L]
   # Thus, if the I variable wasn't found in the default classes list, it will be created
   # as a Decimal variable in the local class ([L])
     Default Local
     For I = 1 To 100 : J+=I : Next I
   # By default, after the 3 instructions above, when a table related variable is declared without class,
   # it will be searched by default in [F:CLI] class, then in [F:PRO] class, then in [F:REP] class,
   # and then in the other [F] classes
   # But if an instruction seach as Read Key=value is used, only the [CLI] table will be considered
     Default File [REP]
     Default File [PRO]
     Default File [CLI]
   # By default, after the instruction above, variables without classes will be searched only
   # in [F:REP], [F:PRO], [F:CLI], [L] classes in that order
     Default file [REP], [CLI], [PRO], [L]
   # By default, after the instruction above, variables without class will be searched only:
   # first, as table variables (in the order given by Default File if any was given
   # then, as local variables, and finally as [C]variables
     Default [F], [L], [C]
   # The default classes should preferably be first [C], then [L],
   # then [V], then the other classes in the usual sequence.
       Default [V] : Default [L] : Default [C]
   # Only class [L] may be used for variables without class
     Default [L], [L]

Comments

The engine manages a list of default classes and default tables. These lists are used to search for variables and to define default arguments.

The list of default tables is modified by:

• The File instruction that only places files declared on the list, in the order in which they are declared.
• The Default File instruction followed by a table abbreviation, which places the table on top of the list.

The list of default classes is modified by:
* The command Default followed by a list of classes, giving a complete list of classes.
* The Default instruction followed by a single class, which places the class on top of the list of default classes.
* The Default instruction followed by a list of classes, which replaces the previous list of classes by the list.

The list of default classes is restored when returning from a subprogram.

By default, in a subprogram, the variable policy creation is Default Local.

Do not to confuse 'Default [L]' and Default Local. The first syntax specifies that a variable, without class, is searched for by default in class [L]; while Default Local specifies that if a variable does not exist, it is created by default in class [L].

Do not omit [S] from the list of classes when giving a complete list in a Default command. In this case, all the engine system variables would become inaccessible, unless the name was always preceded by an [S]. When [F] appears on a list of default classes, all the tables on the list are in their default order.

If there is no `Default` instruction, the default classes used when a script runs are those given by:

Default [S], [L], [V], [M], [F]

Associated errors

7: The class does not exist (for a table, this means it has not been declared in a previous File command).

See also

File, Read, Write, Look, Readlock, RewriteByKey, DeleteByKey, Delete, Update, Local, Global, For.