This behavior enables the definition of recursive tacit verb systems (which involve multiple verbs).
Technically, most practical recursive computations can be performed in J without this. For example, numbers and numeric operations already have recursive definitions and this can be used in many cases. Also, arrays can be used iteratively to achieve the effects of recursive definitions. But, J was designed to present ideas in academic contexts (this is why we have $: but also also why we have monadic definitions for <: >: -: ...). So, anyways, in tacit expressions, J holds off finding the definitions of named verbs until when it's being used. This allows tacit verb definitions to reference verbs which have not yet been defined. FYI, -- Raul On Wed, Nov 6, 2019 at 5:11 AM Henry Rich <henryhr...@gmail.com> wrote: > > https://code.jsoftware.com/wiki/Vocabulary/ErrorMessages#value > > Henry Rich > > On 11/6/2019 4:26 AM, Arnab Chakraborty wrote: > > Dear all, > > > > Here is a behavior that I noticed only recently, and it puzzles me a > > lot: > > > > Let's say abc and xyz are not defined in my J session, and type just abc > > by itself in a line. Of course, I get a value error. But if I type > > > > xyz abc > > > > then J does not produce any error, but simply echos back what I have typed! > > I expected that J would start executing from the right, encounter abc, and > > produce a value error. If I now define abc (say abc=. 0), then > > > > xyz abc > > > > produces a value error (expected) about xyz. > > > > But why does J become silent in presence of multiple undefined symbols? > > ---------------------------------------------------------------------- > > For information about J forums see http://www.jsoftware.com/forums.htm > > > -- > This email has been checked for viruses by AVG. > https://www.avg.com > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
