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I. Locatives

Locative abc_f_ refers to abc in locale f; indirect locative abc__xy refers to abc in the locale whose name is the current value of xy. For compatibility with previous versions, the non-standard abc__ is accepted and is the same as abc_base_. Thus:
   b=: 1
   Rome=: 2
   Rome_NewYork_=: 20
   f_NewYork_=: 3 : '3*b=: Rome+y'
   f_NewYork_ 10
90

   b,Rome
1 2

   b_NewYork_
30
A name is global if it is not assigned by =. within Explicit Definition (:). Every global name is executed in the current locale. Initially, the current locale is base. A locative f_abc_, while it is executing, switches the current locale to abc. The verb 18!:4 also switches the current locale, and 18!:5 gives its name.

The name f_abc_ is executed in locale abc in the sense that a global name referenced in f is sought therein and, if not found, is then sought in the locales in the path of abc (but is still executed in abc). The path of a locale is initially ,<,'z' , except that locale z has an empty path initially, and may be changed using 18!:2 .

A locale is commonly populated by a script, by appropriate naming of the verb used to execute the script. For example, if the file stats contains the script:
   mean=: sum % #
   sum=: +/
Then:
   ssx_z_=: 0!:10             Silent script execution
              
   ssx_a_ <'stats'            Populate locale a

   mean=: 'in base locale'
   mean_a_ 3 4 5
4
              
   ssx_bc_ <'stats'           Populate locale bc
   sum_bc_ 3 4 5
12
The example also illustrates the use of locale paths, in this case the z locale: First, the utility ssx is defined in the z locale. In executing ssx_a_, ssx is not found in locale a and is therefore sought (and found) in locale z. Since ssx_a_ is executed in locale a, the names in the stats script are defined in locale a, populating it thereby. Similarly for ssx_bc_.

See also 18!: in Appendix A and the “Locales” and “Object Oriented Programming” labs distributed with the system.


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