F. Trains

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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 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=:/\
       + 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

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