Rule-based string manipulation

Question

I am studying string manipulation. I have a list of strings all members of which consist of 2 or 3 words followed by a 3 letter capital appreviation of the words, for example

str={A Big Cheese ABC}

I'd like to get two substrings:

str1={A Big Cheese}

and

str2={ABC}

Using UpperCaseQ returning "True" for three characters in a row would appear to be a first step. Any thoughts?

Answer 1

First you need a string pattern that matches your inputs. The first part of your string "A Big Cheese", can be matched by two underscores, __. The last part is always three upper case letters in a row. You can match any upper case letter with

caps = Alternatives @@ (ToUpperCase /@ Alphabet[])

You can see it work here,

StringMatchQ["A", caps]
(* True *)

To catch three capital letters in a row, you can join them using ~~

StringMatchQ["ABC", caps ~~ caps ~~ caps]
(* True *)

StringMatchQ["AbC", caps ~~ caps ~~ caps]
(* False *)

Or you can use Repeated,

StringMatchQ["XYZ", Repeated[caps, {3}]]
(* True *)

Now that we have our pattern we can give it to StringCases. You need to name the patterns and apply a transformation rule

StringCases["A Big Cheese ABC", a__ ~~ b : Repeated[caps, {3}] :> {a, b}]
(* {{"A Big Cheese ", "ABC"}} *)

You can wrap this up into a function, using First to remove the extra curly brackets,

splitSTRING["examine your zipper XYZ"]
(* {"examine your zipper ", "XYZ"} *)

Edit

As march points out you don't have to use Alternatives to make a Pattern, you could use UpperCaseQ to make a PatternTest:

StringCases["A Big Cheese ABC", 
 a__ ~~ b : Repeated[_?(UpperCaseQ), {3}] :> {a, b}]
(* {{"A Big Cheese ", "ABC"}} *)

Answer 2

Since the input strings end with a 3 letter capital abbreviation of the words, you can use StringTake:

StringTake["A Big Cheese ABC", {{1, -5}, -3}]

{"A Big Cheese", "ABC"}

Answer 3

a work around:

str1=StringJoin[Riffle[Most[Flatten[StringSplit[str]]], " "]]

and

str2=Last[Flatten[StringSplit[str]]]