xShuffle ( INPUT ; TIMES )

To shuffle a string

Average rating: 4.1 (22 votes) Log in to vote

Nick Lightbody - Show more from this author
Deskspace Systems Limited
http://deskspace.com

Sample input:

"abcdefghijklmnopqrstuvwxyz";99

Sample output:

xzfrijqpkymcuswvbhdetolnga

Function definition: (Copy & paste into FileMaker's Edit Custom Function window)

// xShuffle
// Nick Lightbody
// September 2015
Let([
s=INPUT; 
c=Case(TIMES<1;1;TIMES);
L=Length(s);
r=Int(L * Middle(GetAsText(Random);3;2)/100); 
x=Middle(s;r;1);
y=Replace (s;r;1;"") & x; 
c=c-1
];
Case( c>0 ; xShuffle( y ; c ) ; y )
)

This is a simple tail recursive function used to create a shuffled string for substitution in an encryption process. Typically the process will use a large number of such substitution strings and hence the need to create a large series required this function.

Each cycle moves random character to the end of the string, hence TIMES must be larger than the length of the string.

Comments

		unix, Japan Jan 13, 2016
Parameter names are different from definition. Why don't you use control to selecting character to move? 1st call you need to select from all chars. 2nd call you need to select from all chars excluding last one, it is already selected before. and so on.

		Nick, Sussex UK Jan 13, 2016
Thanks - I have amended the parameter names. When creating a block of keys, we normally shuffle the normal set of characters say a 1000 times, as it is very quick. In practice the quality of the result is no different. With a longer set of characters, in Japan, perhaps this could be more of an issue? However, on a random shuffle it is best, I think, to select from all every time, not to exclude the last one, since otherwise it is surely less random? Cheers, Nick

		comment, VR Jan 16, 2016
"Each cycle moves random character to the end of the string, hence TIMES must be larger than the length of the string." If you select a random character one at time, move it from the input string to the output string and repeat this until you run out of characters, you will end up with a completely randomized string. There will never be a need to it more times than the length of the input string.

		unix, Japan Jan 20, 2016
xs ( INPUT ; OUTPUT ) /* INPUT: string to shuffle OUTPUT:call with "" / Let ( [ l = Length ( INPUT ) ; r = Int ( Random L ) + 1 ] ; Case ( l < 2 ; OUTPUT & INPUT ; xs ( Replace ( INPUT ; r ; 1 ; "" ) ; OUTPUT & Middle ( INPUT ; r ; 1 ) ) ) )

Note: these functions are not guaranteed or supported by BrianDunning.com. Please contact the individual developer with any questions or problems.

xShuffle ( INPUT ; TIMES )

Comments

Support this website.

Support this website.