H.1  Routines and Variable Scoping

Sheerpower provides a number of ways to organize your code. This becomes very important as your programs grow larger. Programs of over 500,000 lines of code have been written in Sheerpower. These, by the way, compile, link, and run within three seconds of saving a coding change.

A number of types of routines are provided by Sheerpower:

• Global routines -- the default routine type; all variables are global to the program.
• Private routines -- all variables are private to the routine.
• Scoped routines -- just like private routines except all variables are reset upon entry or exit.
• Local routines -- acquire the scoping of the private routine that called them. Used for the rapid abstraction of large routines into a series of smaller ones.

Routine names must start with a letter, include at least one underscore "_", and can contain any number of other letters and digits. By default, all routines are global unless specified otherwise.

When talking about routines, we have to also talk about "variable scoping." Scoping determines which variables can be used and where. Variables outside of any routine are called global or main variables. From outside of a routine, they can be accessed using just their name. They can also be accessed from within a global routine the same way. However, from within a private routine, they must be accessed by prefixing their name with MAIN$. We call this their "fully-qualified name." For example:

x = 45
abc = 999
tax = 9876

routine do_it
  print x       // this will print 45
  print main$x  // this will also print 45
end routine

private routine here_we_go
  x = 101
  print x       // this will print 101
  print main$x  // this will print 45
end routine


my_private
my_regular

private routine my_private
  abc=123
  local do_it_local
end routine


local routine do_it_local
  xyz$ = 'is xyz'
  assert abc=123
  assert xyz$='is xyz'
end routine

routine my_regular: private abc, tax
  abc = 456
  tax = 99
  local do_it_2
  print 'In '; _routine
  debug show abc, my_regular$abc, main$abc, tax, my_regular$tax
end routine

local routine do_it_2
  my_tax = 45
end routine

The fully qualified name of the "x" in the here_we_go private routine is here_we_go$x. Using this suffix method is how Sheerpower keeps track of the scope of variables. It also makes it easy for you to keep track of the scoping of variables.

Sheerpower also supports include directives and modules.

Note: Sheerpower supports recursive routines through the use of memorization techniques. Avoiding traditional recursion gives Sheerpower a significant performance boost -- no data stack to build or tear down. It also makes hacking Sheerpower code virtually impossible using traditional hacking methods.