======Synopsis:======
[[for]] (//once//, //expression//, //each//) { //[[block]]// } \\ 
[[for]] //var// from //firstval// to //lastval// { //[[block]]// } \\
[[for]] //var// from //firstval// to //lastval// step //stepval// { //[[block]]// } \\
[[for]] //var// in (//word list//) { //[[block]]// }

======Description (standard form):======
[[FOR]] is a general purpose loop.  It is modeled on the C for statement,
and works in a very similar manner.  Aside from the action, there are
three parts to a [[FOR]] loop:

The //once// part is a //[[block]]// executed before the loop begins 
iterating.  This is often used for initializing counters and other 
variables that will be used in the loop.

Before each loop iteration, the //condition// expression is checked.  
Most often, this is used to see if the counter has exceeded a certain limit.  
The condition may contain any expression legal in the [[IF]] command.
Because of this, the loop does not necessarily have to iterate at all.

The //each// part is a //[[block]]// executed each time the loop exits and
before the //condition// is tested.  This is where you would increment a
counter that gets checked by the condition statement.

It is imperative to note that the three sections are separated by commas
and not semicolons; this is because //once// and //each// may contain 
semicolons if they contain multiple statements.  This is the reverse of C.
The first and third section are **COMMANDS** and the second section is an
**EXPRESSION**.

//Once//, //each//, and //block// are optional and may be left blank.

======Description (for/next form):======
This second form of the command provides a FOR .. NEXT type loop that
enumerates each of the integers between //firstval// and //lastval//.
Each enumerated integer is assigned to //var// and the //block// is 
executed.

If you wish enumerate only some of the values in the range, you can 
specify a //step//, which says that each //step//th value should be 
enumerated.

If //firstval// is greater than //lastval// then you must specify a 
//step// value and it must be negative.  If you do not do this, then
the loop will not execute.

The //var// variable should be considered read-only.  Changing it will
**not** affect how the range is enumerated.

This form is much cheaper than a standard [[for]], and is cheaper than a [[fe]]
over a [[jot]] range.

The [[CONTINUE]] and [[BREAK]] commands are honored in the action body.
The [[CONTINUE]] command will behave as a "next" operation, and the [[BREAK]]
command will abort the loop entirely.

======Description (for/each form):======
This third and final form is a FOR .. IN LIST type loop that iterates over
each word in the word list, assiging each value in turn to the //var// and
executing the //block//.

This form is cheaper than [[fe]] because it is optimized for iterating 
one word at a time, whereas [[fe]] is general-purpose.

The [[CONTINUE]] and [[BREAK]] commands are also honored in the same way
as in the second form above.

======Examples:======
Form 1:

To display a warning message 3 times:
      for ( @ xx = 3, xx > 0, @ xx-- ) {
         echo WARNING!  This ship will self destruct in $xx seconds!
      }

A infinite loop that behaves like the Unix 'yes' command:
      for ( ,, ) {
         echo yes
      }

Form 2:

Display the numbers 1 through 5 each on a separate line:
      for ii from 1 to 5 {
         echo $ii
      }

Display the numbers 1, 3, and 5 each on a separate line:
      for ii from 1 to 5 step 2 {
         echo $ii
      }

Form 3:

Display the words "one", "two", and "three" each on a separate line:
      for xx in (one two three) {
         echo $xx
      }

======History:======