parsing - Unreachable rules in the Java 8 CFG? -

-

maybe rather in-depth question has idea why in

the java languagespecification - java se 8 edition (2014-03-03)

which defines formal context-free grammar of java 8 in terms of production rules , terminals not defined rules reachable?

the specification describes dozens of rules such as

ifthenstatement:
if ( expression ) statement

or

assertstatement:
assert expression ;
assert expression : expression ;

which make perfect sense.

but strangely of defined rules not reachable others such important rule

type:
primitivetype
referencetype

in total counted following 2 rules not reachable others:

  1. packagename
  2. type

how 1 define complete java 8 cfg having unreachable rules?

often specification authors find convenient formulate rules of spec in terms of non-terminals; sometimes, however, of useful non-terminals not, technical reasons, used in main grammar. in such cases spec defines relevant non-terminals anyway, ground of rules of spec in grammatical formalism.

here, example, rule type sends pretty clear signal types either primitive types or reference types. grammar has number of places primitive types may referenced, , others reference types required. if type not reachable, need not mean syntactic grammar incomplete; may mean in fact there no places in syntactic grammar authors found useful refer type. non-terminal type may nonetheless defined, if spec authors find useful tool of exposition.

in specs appear in multiple versions, reason arises: non-terminal ceases used in main grammar, appropriate definition given avoid breaking other specs refer non-terminal, , allow other specs upgrade gracefully new version of spec containing grammar.

i not know of these reasons applies in case of these non-terminals in java 8, or whether there perhaps other reason.


Comments

Post a Comment

Popular posts from this blog

database - VFP Grid + SQL server 2008 - grid not showing correctly -

-
i having problem, have grid called "gridbasica" , this: thisform.gridbase.recordsource = "sgviemp" sgviemp cursor made executing select sqlserver command sqlexec. when want modify registry, go form , the update there. so, when come form grid, grid isnt grid anymore, big white rectangle. reading around said: delete recordsource , asingt again. thisform.gridbase.recordsource = "" *--i sqlexe here thisform.gridbase.recordsource = "sgviemp" i , works, but, when click button modify again cursos updated modify form doesnt load fields did first time. could me out that? thanks in advance. --------------- edit ------------------ i have been doing recommended: lnselect = select(0) n = sqlexec(thisform.conexion,"select emp_ccodigo codigo, emp_cnombre 'nombre o razon social', emp_cnumrif 'r.i.f' sgviempr","sgviemp1") set echo on suspend select sgviemp zap in sgviemp *-- browse *--zaps correct
Read more

jquery - Set jPicker field to empty value -

-
im using jpicker color selector in form. have clear value set window/icon 'no color selected' state. i've tried following: $(':input[name="color"]').val(''); //access value directly. (does not affect jpicker) 2: $.jpicker.list[0].color.active.val('hex', '', this); //set color black , input value 000000, instead of empty string 3: $.jpicker.list[0].color.active.val(null, '', this); //does nothing none of 3 methods seems behave properly. in advance. this works me :) $.jpicker.list[0].color.active.val('v', null); here example: http://jsfiddle.net/3up7n/
Read more

.htaccess - htaccess convert request to clean url and add slash at the end of the url -

-
ok , searched more 4 days , more 20 posts here in stach or in websites without kind of success first here htaccess file rewriteengine on rewriterule ^([a-za-z0-9_]+)/?$ index.php?page=$1 [nc] rewriterule ^([a-za-z0-9_]+)\/([a-za-z0-9_]+)\/?$ index.php?page=$1&action=$2 [nc] i tried many codes 1 worked me can call request , works me www.example.com/pagename => www.example.com/index.php?page=pagename here questions , please provide me information "in detail" understand code well 1- how convert request automatically www.example.com/index.php?page=pagename www.example.com/pagename 2- if tried add slash @ end shows me page without images or styling mean www.example.com/pagename => works www.example.com/pagename/ => doesn't work that's :) for first part need 301 rule this: rewritecond %{the_request} /index\.php\?page=([^\s&]+) [nc] rewriterule ^ /%1? [r=301,l] for second part use absolute path in css, js, images files r
Read more