Order of execution - adverbs & conjunctions

Adverbs and conjunctions have higher precedence than verbs. This means that an adverb or conjunction is executed before a verb. Furthermore, the left argument of an adverb or conjunction is the entire verb phrase that precedes it. The exact rules for parsing and execution are given in section E of the J Dictionary.

For practical purposes, the following examples illustrate the rules.

   a =. i.2 3
   +/"1 - a
_3 _12

Like all J sentences, the above sentence executes from right-to-left. Before the + can be parsed as being a dyad or a monad, the higher precedence " conjunction executes. The " conjunction takes the 1 as its right argument and the entire verb phrase to its left as its left argument. The verb phrase to the left is the adverb / which takes the + as its left argument. The following uses parentheses to make clear the order of execution that follows from the rules.

   ((+/)"1) (- a)

As mentioned earlier, simple examples with constants may require that you separate the constant that is the conjunction argument from the constant that is the argument of the derived verb.

   a (+"1) 1 2 3
   a +"1 (1 2 3)
   a +"1 [ 1 2 3

The last one uses the monad [ (same) that is defined to just return its argument. This is a bit shorter and avoids the use of parentheses.