Randomizing priority in Prolog predicates -


one of main differences between prolog , first order logic in strict rule priority of right parts in predicate. know if there way randomize priority without renouncing @ normal backtracking behaviour. in particular i'm working swi-prolog solution works interpreter.

although there no built-in way use randomness search strategy in prolog theorem prover, there native functions there generate random numbers used (in roundabout way) randomize instance of predicate chosen consideration next.

to elaborate, might include each instance of predicate path/n 2 additional tests represent range within 0 , 1 predicate holds. range (lo, hi) should chosen such hi - lo = 1 / k, k total number of instances predicate path/n has in knowledgebase.

path(n, ...) :- n >= 0.0, n < 0.2, ... path(n, ...) :- n >= 0.2, n < 0.4, ... path(n, ...) :- n >= 0.4, n < 0.6, ... path(n, ...) :- n >= 0.6, n < 0.8, ... path(n, ...) :- n >= 0.8, n <= 1.0, ...

with embedding of ranges, making instances of path/n equally considered. whenever path/n called in rhs of rule or production (right of :- or -->), should preceded generation of random float between 0 , 1 passed first argument path/n; e.g. foo :- random(n), path(n, ...)..

this of course become cumbersome on time knowledge base increases in size, might want write compiler (like dcg compiler) generates randomness threading you. writing these sorts of compilers in prolog surprisingly not work predicates asserta , assertz.

if using "random derivation search" method avoid infinite left recursion, know nicer method might write solution uses breadth-first search rather prolog's intuitive depth-first. involved threading state argument predicates (worth google: prolog breadth-first).

edit: prolog higher-order logic (hol), except in strict left-derivation, first-predicate-first-considered way, leads problems left recursion. use (hol) features of prolog model search approach considers predicates evenly (assuming predicates pure predicates, no arithmetic, etc.). example, store right hand sides list of predicates [[p1, p1a1,...],[p2,p2a1,...]|_], randomize list before evaluation, evaluate shuffled list of predicates iteratively building predicate using =.. operator, i.e. x =.. [p1, p1a1, p1a2], x. x in snippet unified p1(p1a1,p1a2), , searched satisfiability.


Comments

Post a Comment

Popular posts from this blog

android - InAppBilling registering BroadcastReceiver in AndroidManifest -

i'm implementing inapp billing in android app. works well, however, i'm trying decouple broadcast receiver activity manifest. suggestion in android's trivialdrive sample: // important: dynamically register broadcast messages updated purchases. // register receiver here instead of <receiver> in manifest // because call getpurchases() @ startup, therefore can ignore // broadcasts sent while app isn't running. // note: registering listener in activity bad idea, done here // because sample. regardless, receiver must registered after // iabhelper setup, before first call getpurchases(). currently there's class extends broadcastreceiver : public class iabbroadcastreceiver extends broadcastreceiver { /** * intent action receiver should filter for. */ public static final string action = "com.android.vending.billing.purchases_updated"; private final iabbroadcastlistener mlistener; public iabbroadcastreceiver(iabbroadcastlistener listener) { m...
Read more

python Tkinter Capturing keyboard events save as one single string -

is possible store keyboard events 1 string? code below stores 1 char , prints it. card reader or bar code reader, contains collection of character/ string not 1 character @ time. goal save char pressed text variable. from tkinter import * root = tk() def key(event): text= event.char text+= event.char print ("pressed", text) def callback(event): frame.focus_set() print ("clicked at", event.x, event.y) frame = frame(root, width=100, height=100) frame.bind("<key>", key) frame.bind("<button-1>", callback) frame.pack() root.mainloop() currently, creating text variable , everytime key() function gets called, , text stores last character typed. you can define text module level variable , , use module level text inside key function - text = '' def key(event): global text text+= event.char print("pressed", text)
Read more

sql server - Why does Linq-to-SQL add unnecessary COUNT()? -

here tables: create table customer ( cid int primary key, name varchar(32) ) create table ord ( oid int primary key, cid int foreign key references customer, address varchar(20) ) here's linq-to-sql statement: var aaa = c in db.customer select new { c, o = c.ord.tolist() }; and here's inexplicable query generated linq-to-sql: select [t0].[cid] [cid], [t0].[name] [name], [t1].[oid] [oid], [t1].[cid] [cid2], [t1].[address] [address], (select count(*) [dbo].[ord] [t2] [t2].[cid] = [t0].[cid]) [value] [dbo].[customer] [t0] left outer join [dbo].[ord] [t1] on [t1].[cid] = [t0].[cid] order [t0].[cid], [t1].[oid] i want understand how rid of count(*) part. it's entirely uncalled for! linq needs count(*) in order determine number of entries returned o = c.ord.tolist() .
Read more