Vocabulary/eqco

=: (Is (Global)) Noun/Other

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Is (Global or Local), also called Copula, changes the value of a given target.

A sentence using Copula =: is always of the form: target =: value.

Likewise a sentence using Copula =. is always of the form: target =. value.

The target can be any valid J identifier, or an expression which evaluates to a boxed or unboxed list of one or more valid J identifiers.

   'fe fi'=: 100+ 0 1     NB. the target is a string representing two J words
   ]fo=: fe+fi            NB. the target is a J word: fo, the value is a noun expression
201
   fe ; fi ; fo
+---+---+---+
|100|101|201|
+---+---+---+
   fum=: 1&+              NB. the target is a J word: fum, the value is a tacit verb definition
   ]fo=: fum fo           NB. the value is an expression in the verb: fum, it changes the J word: fo
202

The target can also be an expression which evaluates to the required J word(s). Putting parentheses around the target ensures that it is evaluated before the Copula is applied.

   aa=: 'a' , ":               NB. aa is a verb which creates a suffixed J word: 'a*'
   aa each 1 2                 NB. Two such J words, suffixed: '1' and '2'
+--+--+
|a1|a2|
+--+--+
   (aa each 1 2)=: 200+ i.2    NB. creates scalar nouns of the above J words
   a1 ; a2
+---+---+
|200|201|
+---+---+

Common uses

Used to create nouns, adverbs, conjunctions and verbs, the building-blocks of an application.

See Also

• Is (Local)

• Entry in the J Dictionary for =:

CategoryVoc