[Jprogramming] A templating framework for J expressions

Fri Sep 11 13:39:18 UTC 2020

Much appreciated. 
I have got something to chew on, thanks.

R.E. Boss

-----Original Message-----
From: Programming <programming-bounces at forums.jsoftware.com> On Behalf Of 'Pascal Jasmin' via Programming
Sent: vrijdag 11 september 2020 15:09
To: programming at jsoftware.com
Subject: Re: [Jprogramming] A templating framework for J expressions

Its an easier way to write functions that include multiple parameters, modifiers as parameters, lets you bind/curry any combination of those parameters, and provides easy autoquoting of a parameter in chosen circumstances.  It behaves like extra u v x y parameters with multiple substitutions of each token, though for that exact behaviour parentheses around either the data-parameter or the token-variable need to be included.  WIthout parentheses, the templating engine can insert any string into the template, and so fragment combinations of linear expressions is possible.  

A walkthrough of some of the functions

bb =: 1 : 'dltb each (''`''&cut) m'

used to cut linear representations on ` .  This is a helper function that simplifies parameter building.  Similar to traditional language function call that cuts parameters on ",".  ` is used because there are better gerund builder functions for J, and so ` is non essential.  Templates discard the 2: to 9: and _2: to _9: verbs from use, as they too are non essential, and happen to not appear in the addon library.

' `% `# ' bb

┌┬─┬─┐

││%│#│

└┴─┴─┘

builds 3 parameters.  A null parameter passed to template leaves its corresponding token unbound.  It is also possible to pass a verb or noun directly to template that will just bind the first (lowest magnitude) parameter.

NoteV_z_ =: 1 : '(0 (0 :)) label_. 0 (m :)'

Allows embedding documentation in an explicit function.  Adverb where m is the left parameter to :  .  Can be enhanced to provide side effect database/dictionary/queryable function documentation. 

jt is the templating engine conjunction.  Its documentation string:

template n includes tokens in form of number colon (except for 0: 1:). if n string it is tokenized.

those tokens will be replaced with blocked string expressions in m

a repeated token gets replaced multiple times.

a negative token gets replaced by the quoted m block.

m blocks will replace right to left in order of sorted token absolute values (ie. if tokens are 2: _3: 5:, leftmost of 3 m blocks will replace 5: Rightmost will replace 2:)

a null('') m block skips the token binding. Replaces token with +100 magnitude. Therefore limit of 100 unique replacement tokens.

too short of an m list, just partially binds the lowest magnitude token values.

an unboxed u (verb) parameter is replaced with a single boxed lr. unboxed m is boxed. Less efficient to pass one parameter at a time, but supported.

if not fully bound, returns (jt n) adverb with n partially bound tokens.

if fully bound, returns result string

multiline n can be coerced into ` delimited single line to fit this function.

The Jxp function turns a string into an explicit or tacit expression based on its content.  It also is in embedded documentation format.

One of the practical applications of this templating engine is creating/enabling "modifier trains" that mix conjunctions and adverbs.  Examples of how those modifier trains should bind parameters is provided, but it is easy to create alternatives.  A next step is a function that takes a series of adverbs and conjunctions, that autobuilds a train of CC CA AC combinators based on the parameter types. 

On Friday, September 11, 2020, 05:45:43 a.m. EDT, R.E. Boss <r.e.boss at outlook.com> wrote: 

Am I the only one who don't understand a word of this high-browed J?
Even not why I should make an effort to digest it. 

R.E. Boss

-----Original Message-----
From: Programming <programming-bounces at forums.jsoftware.com> On Behalf Of 'Pascal Jasmin' via Programming
Sent: vrijdag 11 september 2020 05:42
To: Programming forum <programming at jsoftware.com>
Subject: [Jprogramming] A templating framework for J expressions

cocurrent 'z'

NB. utilities pasted from jpp, hopefully did not forget any:

NoteV_z_ =: 1 : '(0 (0 :)) label_. 0 (m :)'
bb =: 1 : 'dltb each (''`''&cut) m'
lrA =: 1 : '5!:5 < ''u'''
eval =: 1 : 'if. 2 ~: 3!:0 m do. m else. a: 1 : m end.'

numcolonnot01 =: {.@((0 1 _1 -. at e.~ ".@}:) *. ':' = {:)`0:@.('''' = {:)

a2blr =: 1 : 'if. 3 = nc <''u'' do. < u lrA else. boxopen m end.'

jt =: 2 NoteV

template n includes tokens in form of number colon (except for 0: 1:). if n string it is tokenized.

those tokens will be replaced with blocked string expressions in m

a repeated token gets replaced multiple times.

a negative token gets replaced by the quoted m block.

m blocks will replace right to left in order of sorted token absolute values (ie. if tokens are 2: _3: 5:, leftmost of 3 m blocks will replace 5: Rightmost will replace 2:)

a null('') m block skips the token binding. Replaces token with +100 magnitude. Limit of 100 unique replacement tokens.

too short of an m list, just partially binds the lowest magnitude token values.

an unboxed u (verb) parameter is replaced with a single boxed lr. unboxed m is boxed. Less efficient to pass one parameter at a time, but supported.

if not fully bound, returns (jt n) adverb with n partially bound tokens.

if fully bound, returns result string
multiline n can be coerced into ` delimited single line to fit this function.

)

n =. ;:^:(0 = L.) n

m =. |. u a2blr

Ilist =. I. {. at numcolonnot01 &> n

nlist =. ".@}: each Ilist { n NB. numeric version of each n: param.

'too many parameters given' assert (#m) <: # ~. | each nlist

snlist =. /:@:( (| , ]) each) nlist

r =. m #~ (#m) {. #/.~ snlist { | each nlist

a =.|: jthelper r ,. (nlist (,<)"0 Ilist) {~ snlist {.~ #r

n =. ({. a) (; {: a)} n

if. 1 e. numcolonnot01 &> n do. (jt n) else. ;:inv L:1 <^:(1 = L.) n end.

)

jthelper =: 3 : 0("1)

'a b c' =. y

if. '' -: a do. a =. ':' ,~ ": (* * 100 + |) b

elseif. 0 > b do. a=. quote a end.

a;c

)

Jxp =: cutLF v2a 1 NoteV

creates tacit or explicit expression based on m.

m is either string (auto boxed to 1) or "multiline equivalent" boxed format.

if includes v/n, explicit conjunction

if includes u/m, explicit adverb

if includes x but not single line :, explicit dyad

if includes y, explicit monad

else tacit or noun expression, eval'd if not multiline.

)

if. 1 = #m do. m =. (>m) bb end. NB. ` is coded multiline

m =. ;: each m

if. +./ , (;: 'v n') e.S:1 m do. 2 : (;: inv each m)

elseif. +./ , (;: 'u m') e.S:1 m do. 1 : (;: inv each m)

elseif. (0 = (< ;: ':') e. m) *. +./ (;: 'x') e.S:1 m do. 4 : (;: inv each m)

elseif. +./ (;: 'y') e.S:1 m do. 3 : (;: inv each m)

elseif. 1 = #m do. (> ;: inv each m) eval else. ;: inv each m end.

)

some examples this permits are an easy way to create conjunction trains:

CC =: 2 : '( u ; v ) jt ''u (4: 3:) (2: v)'' Jxp'

CA =: 2 : '( u ; v ) jt ''(u 3: v) 2:'' Jxp'

AC =: 2 : '( u ; v ) jt ''(u 3:) 2: v'' Jxp'

CC is a conjunction that returns an adverb that returns a conjunction (3/5 parameters total)

+: +'@' CC '@:'-  NB. binding order same as if it were called in multi adverb form.

+ at +:@:-

The same function can be done with more flexible bindings as a 5 parameter adverb:

' `+:` `@` ' bb jt '5: (4: 3:) (2: 6:)' Jxp

(jt(;:'+:(104:@)(102:106:)'))Jxp

'+`-` @:' bb ' `+:` `@` ' bb jt '5: (4: 3:) (2: 6:)' Jxp

- at +:@:+

Both the CC and 5-adverb version are much easier to write and read than the nested quote monstrocity that is the alternative.

Jxp is a suggestion I believe Henry made on wiki.  At first, I didn't like it because the intent of a function is both usefully described, and an early intentional decision.  But it is convenient when that initial intent can change:

'+`-` @:' bb ' `+:` `@` ' bb jt '5: (4: 3:) (2: 6:) y' Jxp

 '@`@:' bb jt '+ _3: CC _2:' Jxp  NB. negative token markers get quoted before replacement.

2 : 'u ( + @ ) ( @: v )'
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