maskedPattern

Use maskedPattern to display a variable in place of a complicated pattern expression.

Build a pattern that matches simple arithmetic expressions composed of numbers and arithmetic operators.

mathSymbols = asManyOfPattern(digitsPattern | characterListPattern("+-*/="),1)

mathSymbols = pattern
  Matching:

    asManyOfPattern(digitsPattern | characterListPattern("+-*/="),1)

Build a pattern that matches arithmetic expressions with whitespaces between characters using mathSymbols.

longExpressionPat = asManyOfPattern(mathSymbols + whitespacePattern) + mathSymbols

longExpressionPat = pattern
  Matching:

    asManyOfPattern(asManyOfPattern(digitsPattern | characterListPattern("+-*/="),1) + whitespacePattern) + asManyOfPattern(digitsPattern | characterListPattern("+-*/="),1)

The displayed pattern expression is long and difficult to read. Use maskedPattern to display the variable name, mathSymbols, in place of the pattern expression.

mathSymbols = maskedPattern(mathSymbols);
shortExpressionPat = asManyOfPattern(mathSymbols + whitespacePattern) + mathSymbols

shortExpressionPat = pattern
  Matching:

    asManyOfPattern(mathSymbols + whitespacePattern) + mathSymbols

  Use details to show more information

Create a string containing some arithmetic expressions, and then extract the pattern from the text.

txt = "What is the answer to 1 + 1? Oh, I know! 1 + 1 = 2!";
arithmetic = extract(txt,shortExpressionPat)

arithmetic = 2x1 string
    "1 + 1"
    "1 + 1 = 2"

Use maskedPattern to display a specified name for a complicated pattern expression.

Build two patterns: one that matches words that begin and end with the letter D, and one that matches words that begin and end with the letter R.

dWordsPat = letterBoundary + caseInsensitivePattern("d" + lettersPattern + "d") + letterBoundary;
rWordsPat = letterBoundary + caseInsensitivePattern("r" + lettersPattern + "r") + letterBoundary;

Use maskedPattern to display a specified name in place of the pattern expressions. Build a pattern using the masked patterns that find words that start and end with D followed by a word that starts and ends with R.

dWordsPat = maskedPattern(dWordsPat,"Words that start and end with D");
rWordsPat = maskedPattern(rWordsPat,"Words that start and end with R");
dAndRWordsPat = dWordsPat + whitespacePattern + rWordsPat

dAndRWordsPat = pattern
  Matching:

    Words that start and end with D + whitespacePattern + Words that start and end with R

  Use details to show more information

Create a string, and then extract the pattern from the text.

txt = "Dad, look at the divided river!";
words = extract(txt,dAndRWordsPat)

words = 
"divided river"

Create custom pattern functions and use maskedPattern to hide details.

function newPat = atLeastOneOfPattern(pat)
arguments
    pat pattern
end

newPat = asManyOfPattern(pat,1);
newPat = maskedPattern(newPat,compose("atLeastOneOfPattern(%s)",pat));

end

newPat = atLeastOneOfPattern("a")

newPat = 

  pattern

  Matching:

    atLeastOneOfPattern("a")

  Show all details

Create a pattern hexDigit that matches numeric characters from 0-9 and letters from a-f with characterListPattern. Since characterListPattern is case sensitive, use caseInsensitivePattern so that hexDigit matches regardless of character case.

hexDigit = characterListPattern('0','9') | characterListPattern('a','f');
hexDigit = caseInsensitivePattern(hexDigit);
hexDigit = maskedPattern(hexDigit)

hexDigit = pattern
  Matching:

    hexDigit

  Use details to show more information

hexDigit matches individual digits of hexadecimal numbers. Match full hexadecimal numbers by building a pattern that matches the literal text "0x" followed by one or more occurrences of hexDigit.

hexNumberPattern = "0x" + asManyOfPattern(hexDigit, 1)

hexNumberPattern = pattern
  Matching:

    "0x" + asManyOfPattern(hexDigit,1)

  Use details to show more information

Use this pattern to extract hexadecimal numbers from a string.

hexNumbers = extract("The answer is 0x2A", hexNumberPattern)

hexNumbers = 
"0x2A"