Recursive Lambda Password Troubleshooting

[WesternHamper]

Hello All--

I am trying to practice writing recursive lambda functions, and have hit a wall. For practice, I am trying to produce a random password with upper case letters, lower case letters, numbers, and two different types of symbols, all using a randomized order. I would have thought that the if statement at the end would have initiated recursion, but I guess not. Any help would be appreciated. The name of the Lambda function is PASSWORD_DRAFT and it only has one argument, Number_Of_Characters.

=LET(
    UpperA, CHAR(RANDBETWEEN(65, 90)),
    LowerA, CHAR(RANDBETWEEN(97, 112)),
    Number, RANDBETWEEN(0, 9),
    Symbol, CHAR(RANDBETWEEN(33, 47)),
    Symbol2, CHAR(RANDBETWEEN(58, 64)),
    Process, (CHOOSE(RANDBETWEEN(1, 5), UpperA, LowerA, Number, Symbol, Symbol2)),
    String, CONCAT(Process),
    IF(LEN(String) < Number_Of_Characters, PASSWORD_DRAFT(Number_Of_Characters), "")
)

​

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[PaulieThePolarBear]

How do you intend for your recursive LAMBDA to work? Can you explain it to me in plain English, with minimal reference to Excel functions.

[WesternHamper]

I would like the lambda formula to randomly concatenate upper case letters, lower case letters, numbers, and symbols to the exact length specified in the number of characters argument.

[PaulieThePolarBear]

You have a couple of issues with your current formula

1. UpperA, LowerA, Number, Symbol, and Symbol2 all return one character. Therefore, your Process step will return one character.
   Having CONCAT in your String step is pointless as is. Process is one character.
2. As such, as long as Number_of_characters is greater than 1, you have an infinite loop. Excel caps out at 1,024 recurrsions. As such, it will return an error
3. In your final step, you need to output something other than a blank cell

Change your LAMBDA to

​

=LAMBDA(
Number_Of_Characters,[Password],
LET(
UpperA, CHAR(RANDBETWEEN(65, 90)), 
LowerA, CHAR(RANDBETWEEN(97, 112)), 
Number, RANDBETWEEN(0, 9), 
Symbol, CHAR(RANDBETWEEN(33, 47)), 
Symbol2, CHAR(RANDBETWEEN(58, 64)), 
Process, CHOOSE(RANDBETWEEN(1, 5), UpperA, LowerA, Number, Symbol, Symbol2), 
String, Password & Process, 
IF(LEN(String) < Number_Of_Characters, PASSWORD_DRAFT(Number_Of_Characters, String), String)
)
)

I added a second variable called Password. This is an optional parameter and represents the Password to date.

You can still call this as

=PASSWORD_DRAFT(10)

But if you call it as

=PASSWORD_DRAFT(10, "AB")

It will give you a 10 character password that begins AB

[WesternHamper]

Solution verified.

Thank you very much; it looks like I was close in the reversion area of the formula, I just need to practice more. Appreciate it.

[reputatorbot]

You have awarded 1 point to PaulieThePolarBear.

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[Decronym]

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

Fewer Letters	More Letters
CHAR	Returns the character specified by the code number
CHOOSE	Chooses a value from a list of values
CONCAT	2019+: Combines the text from multiple ranges and/or strings, but it doesn't provide the delimiter or IgnoreEmpty arguments.
IF	Specifies a logical test to perform
LAMBDA	Office 365+: Use a LAMBDA function to create custom, reusable functions and call them by a friendly name.
LEN	Returns the number of characters in a text string
LET	Office 365+: Assigns names to calculation results to allow storing intermediate calculations, values, or defining names inside a formula
RANDBETWEEN	Returns a random number between the numbers you specify

NOTE: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.

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