wildcardPattern

The function wildcardPattern is lazy, which means it matches as few characters of any kind as needed, even zero.

Extract a wildcardPattern from a string. There are empty strings between any two consecutive characters in a string, as well as before the first character and after the last. That is why extract matches and extracts five empty strings from this string.

txt = "lazy";
emptyStr = extract(txt,wildcardPattern)

emptyStr = 5x1 string
    ""
    ""
    ""
    ""
    ""

strlength(emptyStr)

ans = 5×1

     0
     0
     0
     0
     0

If wildcardPattern is bounded by other patterns, it matches a minimum number of characters for the pattern expression to match.

txt = "aa aba abaa a a123a a!?.a";
pat = "a" + wildcardPattern + "a";
extract(txt,pat)

ans = 6x1 string
    "aa"
    "aba"
    "aba"
    "a a"
    "a123a"
    "a!?.a"

Use wildcardPattern to match individual characters of all types.

Read the text from Shakespeare's Sonnets with the fileread function and convert it to string.

sonnets = string(fileread('sonnets.txt'));
strip(extractBetween(sonnets,"Shakespeare","But"))

ans = 
    "I
     
       From fairest creatures we desire increase,
       That thereby beauty's rose might never die,"

Create a pattern, pat, that matches one character of any type. Extract the pattern. Convert the string array characters to categorical so that it is a valid input for histogram. Display the occurrences of each character using histogram.

pat = wildcardPattern(1);
characters = extract(sonnets,pat);
characters = lower(characters);
characters = categorical(characters);
histogram(characters)

Create txt as a string. Create a pattern that matches a white space followed by two to three wildcard characters followed by a letter. Extract the pattern from txt.

txt = "1a 23b 456c 7890d";
pat = " " + wildcardPattern(2,3) + lettersPattern;
extract(txt,pat)

ans = 2x1 string
    " 23b"
    " 456c"

Separate a comma-separated list by using wildcardPattern.

Create txt as a string. Build a pattern using wildcardPattern that matches as many characters of any type except "," followed by whitespace characters. Extract the pattern.

txt = "1 fish, 2 Fish, [1,0,0] fish, [0,0,1] fish";
exceptPat = "," + whitespacePattern;
pat = asManyOfPattern(wildcardPattern(1,inf,"Except",exceptPat),1);
extract(txt,pat)

ans = 4x1 string
    "1 fish"
    " 2 Fish"
    " [1,0,0] fish"
    " [0,0,1] fish"