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Index  Generation  JavaScript  for  Random  Go Problem  Selection

RANDPROB JavaScript (stand-alone) is a code insert that generates "n+1" random indexes used for selection of Go problem names from the predefined sectioned Go problem array representing Go problem selection list.  RANDPROB.JS contains a sample of Go Problem name array definition and code for random indexes selection.

RANDPROB JavaScript is a stand-alone one, which means that it s kept in a separate RANDPROB.JS file that gets included into HTML <BODY> (normally at its start and always after the the include defining the Go Problem array) using the following operator (directory levelling may vary):


       <SCRIPT LANGUAGE=JavaScript SRC=PROBLEMS.JS></SCRIPT>
       <SCRIPT LANGUAGE=JavaScript SRC=RANDPROB.JS></SCRIPT>
     
Included JavaScript code is executed in place to generate random indexes that are used for Go Problem selection in the HTML code below JavaScript insert.

Note:

Before reading further you might want to look at explanation of the expression used to generate an integer random number within the specified range.



<!-- Generate Indexes for Random Go Problem Selection  01/08/200101/24/2001 -->
<!-- ------------------------------------------------------------ 01/24/2001 -->
<!-- www.davar.net/GO/PROBLEMS/RANDPROB.JS                                   -->
<!-- Copyright (C) 2001 by Vladimir Veytsel                                  -->
<!--

// RANDPROB is a code insert that is used to generate random indexes for
// selection of problem names from sectioned problem list.

// Code presumes that the array of problem names is declared and initialized.
// The variables that split problem list into sections should have their
// values assigned as in the example below:

// P=new Array(14)   // Problem array (dynamically sized; starts from "0")
// S=new Array( 7)   // Section array (dynamically sized; starts from "0")

// S[ 0]=0           // Used for uniform treatment of section ranges

// P[ 1]="TSJBOW01"

// S[ 1]=1           // End of 1-st section (Break Out)

// P[ 2]="TSJCCT01"

// S[ 2]=2           // End of 2-nd section (Capture Cutting Stone)

// P[ 3]="TSJCLB01"
// P[ 4]="TSJCLH01"
// P[ 5]="TSJCLH02"
// P[ 6]="TSJCLK01"
// P[ 7]="TSJCLK02"
// P[ 8]="TSJCLS01"

// S[ 3]=8           // End of 3-rd section (Capture to Live)

// P[ 9]="TSJCST01"

// S[ 4]=9           // End of 4-th section (Capture Stones)

// P[10]="TSJCNT01"

// S[ 5]=10          // End of 5-th section (Connect Stones)

// P[11]="TSJMSS01"
// P[12]="TSJMSS02"
// P[13]="TSJMSS03"

// As a result of the execution of the code below the random indexes will be
// generated to be used within HTML text for random problem selection (using
// "document.write"):

// i[0]  Random index within entire list that differs from all section indexes
// i[n]  Random index within n-th section

// Warning: If the total number of problems in the problem list is equal
//          to the number of sections, index "i[0]" will be equal to one
//          of the section indexes.

   i=new Array(S.length)     // Index array (dynamically sized; starts from "0")

   S[S.length-1]=P.length-1  // End of last section
           Total=P.length-1

   i[0]=Math.floor(Math.random()*Total)%Total+1

   for (n=1;n<S.length;n++)
       i[n]=(i[0]%(S[n]-S[n-1]))+S[n-1]+1  // Random index within n-th section

// Random index within the entire list (differs from all section indexes)
   if (Total>S.length-1)  // Prevent infinite cycle
      {Valid=false        // Index valid flag
       while (!Valid)     // Repeat until valid index is generated
             {i[0]=Math.floor(Math.random()*Total)%Total+1
              for (n=1;n<S.length;n++)
                  {Valid=(i[0]!=i[n])
                   if (!Valid) break
                  }
             }
      }

//-->
  

RANDPROB JavaScript is a generalization of a similar RANDSONG.JS JavaScript, which performs the same task of random selection, but operates on a list divided into exactly 3 sections a typical special case used for Russian song lists at this web site (see sample song list).


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