Eng:Checking if a String Contains a String

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To check if a string contains another specified string within, each possible combination of orderly characters must be checked throughout the original string to test if it matches the string being checked for containment accuracy. This tutorial shows a scripting method used to check if "string a" contains "string b".

Note:

This article differs from Checking if a String Contains Characters because the string being checked must be in sequential order when searched in the following scripts.

Group-Push Algorithm

The most efficient method involves grouping an individual selection of the string and then grouping the next selection one character forward, checking the condition each time. For this tutorial, assume the following:

• "condition" is a variable used for returning true or false if the string contains the string
• "grouper" is a variable used for grouping a particular sequence of the string
• "i" is a variable for iterating to the next group
• "x" is a variable for iterating and forming the group itself

define check if string (base) contains (sub) //run without screen refresh
set [condition v] to [false] //starts out as false, may become true
set [i v] to (1)
repeat (((length of (base)) - (length of (sub))) + (1))
  if <(condition) = [false]>
   set [grouper v] to [] //this begins the grouping with a blank string
   set [x v] to (i)
   repeat (length of (sub)) //this groups together the current sequence
      set [grouper v] to (join(grouper)(letter (x) of (base)))
      change [x v] by (1)
   end
   if <(grouper) = (sub)>
      set [condition v] to [true]
   end
   change [i v] by (1)

Alternate Algorithm

This algorithm is less efficient and takes up more processing power but can be used anyways. For this algorithm, assume the following:

• "starting letter" is the variable used to define what letter the current combination begins with.
• "ending letter" is the variable used to define what letter the current combination ends with.
• "letter#" is the variable used to define what specific letter if the string is being added on.
• "changer" is the variable used to combine and check each possible combination.
• "output" is the variable used to respond "true" or "false" based on the condition of "string b" being within "string a"

For this script to work efficiently and correctly, run the custom block without screen refresh.

define check if [string a] contains [string b] //the custom block is checking if "string b" is in any combination in "string a"
set [output v] to [false] //because it will turn true throughout the combinations, if so
set [starting letter v] to [1] //sets the base letter originally to "1" for organization
set [ending letter v] to (length of (string a))
repeat (length of (string a)) //because the base, starting letter must be iterated by "1" by the length of the string itself
set [changer v] to [] //set it to nothing so far
repeat (length of (string a)) //to iterate through "string a" while changing the ending letter by "-1" the length of "string a"
set [letter# v] to (starting letter) //so the first letter is added on
repeat (((ending letter) - (starting letter)) + (1)) //so it tests the combination consisting of all characters from the starting letter to the ending one
set [changer v] to (join (changer) (letter (letter#) of (string a)) //adds a letter to the combination
change [letter# v] by (1) //moves on to the next letter to add to the combination
if <(changer) = (string b)> then //checks if the combination is true and within "string a"
set [output v] to [true] //shows that "string b" is within "string a"
end
end
change [ending letter v] by (-1) //for testing out the next combination group with the same base, starting letter
set [changer v] to [] //resets the variable to prepare for a new group of combinations
end
set [changer v] to [] //resets the variable
change [starting letter v] by (1) //prepares for the next combination group with each combination beginning with the next base letter
set [ending letter v] to (length of (string a)) //since the "ending letter" value decreases by "1" each group
end
if <(string a) = (string b)> then //for the case of "string a" and "string b" both being blank and the above script not functioning therefore
set [output v] to [true]

See Also

• Checking if a String Contains Characters

— a similar script that does not require the characters to be in sequence

• Splitting a String
• String