WolframLang: String pattern (regex)

RegularExpression

RegularExpression

Represents a string pattern. Used in functions that takes a pattern. RegularExpression

RegularExpression example

(* match any single character *)
StringCases["😅abc", RegularExpression[ "." ] ]
(* {"😅", "a", "b", "c"} *)

(* match a word char, one or more times *)
StringCases["😅abc", RegularExpression["\\w+"]]
(* {"abc"} *)

(* match a word char, one or more times *)
StringCases["πσ😅ps", RegularExpression["\\w+"]]
(* {"πσ", "ps"} *)

(* match 2 literal char, ignore case *)
StringCases["πσ😅ps", RegularExpression["ΠΣ"], IgnoreCase -> True]
(* {"πσ"} *)

RegularExpression Captured Groups

Captured patterns can be represented by $1, $2 etc, and $0 represents the whole matched string.

StringCases[  "some 172 " , RegularExpression[ " (\\d+) *$" ] -> "$1" ] === {"172"}

StringExpression

StringExpression

Represents a string pattern, but syntax based Wolfram's symbolic pattern matching syntax. Used in functions that takes a pattern. StringExpression

StringExpression example

(* match any single character *)
StringCases["😅abc", StringExpression[ _ ] ]
(* {"😅", "a", "b", "c"} *)

(* match a letter char, one or more times *)
StringCases["😅abc", StringExpression[LetterCharacter..]]
(* {"abc"} *)

(* match a letter char, one or more times *)
StringCases["πσ😅ps", StringExpression[LetterCharacter..]]
(* {"πσ", "ps"} *)

(* match 2 literal char, ignore case *)
StringCases["πσ😅ps", StringExpression[ "ΠΣ"], IgnoreCase -> True]
(* {"πσ"} *)

RegularExpression vs StringExpression

On syntax, the RegularExpression syntax is more widely understood. StringExpression is more readable.

They almost have the same power, except:

• RegularExpression allows you to have lookahead/lookbehind, and repeats of a given length.
• StringExpression allows you to have condition test by expression (pattern/;expr) and or conditions test by function (pattern?functionQ), and orderless matching AnyOrder[ pattern1, pattern2, pattern3 ]. Also, you can embed RegularExpression in it.

for tutorial, see https://reference.wolfram.com/language/tutorial/WorkingWithStringPatterns.html