F. Trains

An isolated sequence, such as (+ */) , which the
“normal” parsing rules do not resolve to a single part of speech is
called a train, and may be further resolved as described below.

A train of two or three verbs produces
a verb and (by repeated resolution), a verb train of any length also produces a
verb. For example, the trains +-*% and +-*%^ are
equivalent to +(-*%) and +-(*%^).
The production is defined by the following diagrams:

         HOOK                FORK             CAPPED FORK
      g       g           g        g            g     g
     /      /          /       /            |     |
    y   h   x   h       f   h    f   h          h     h
        |       |       |   |   /  /          |    / 
        y       y       y   y   x y x y         y   x   y

For example, 5(+*-)3 is (5+3)*(5-3).
If f is a cap ([:)
the capped branch simplifies the forks to g h y and g x h y .
The train N g h (a noun followed by two verbs) is equivalent
to N"_ g h .
The ranks of the hook and fork are infinite.

A two-element train of a conjunction with a noun or a verb produces an adverb.
For example, &.> produces an adverb that might be called “each”,
and the adverb bc=:<" might be called “box cells”
because, for example, 0 bc x would box the atoms of x .

Finally, a train of two adverbs produces an adverb, and (by implication) a train of any
number of adverbs also produces an adverb. For example, / is the adverb “insert scan”,
and ~/~ is the “commuted table”. For example:

   + is 1 2 3 4 5
1 3 6 10 15
   ct=: ~/~
   - ct 1 2 3
 0  1 2
_1  0 1
_2 _1 0