Rubyist Magazine Ruby 2 Ruby Ruby 0, 1, 2, 3 values 1. Regular Expressions The Bastards Book of Ruby. Obviously, we want to use the power of regexes in our code, not just in our text editor environment. Ruby provides a Regexp class and several handy methods. Mix these with scripting logic to make powerful data cleaningsearching tools. The gsub method for strings. Substituting characters in strings is one of the most common uses for regexes in code. To do this, strings have the sub method, which is short for substitution. The sub method takes in two arguments either a String or a Regexp patterna String to substitute in for the first time that the pattern in the first argument matches the invoking string. My cat eats catfood. My dog eats catfood. If you passed in cat, youd get the same result as above, as the letters cat match their literal values. My cat eats catfood. My dog eats catfood. Planet Of The Apes Full Movie Free Download In Hindi Hd. In most scenarios, well want to replace all occurrences of a pattern, not just the first one. This Singapore food guide includes 25 dishes that you should eat, and the hawker stalls and restaurants where you can eat them. Get ready to start eating Get the latest news and analysis in the stock market today, including national and world stock market news, business news, financial news and more. So we use the gsub method, which is short for global substitution. My cat eats catfood. My dog eats dogfood. Once again, passing in the regexp cat would net you the same result. Screen-Shot-2014-08-27-at-10.44.24.png' alt='Ruby File Gets Chomp' title='Ruby File Gets Chomp' />Read a file line by line You are encouraged to solve this task according to the task description, using any language you may know. Lets try a more complicated string. My cat goes catatonic when I concatenate his food with Muscat grapes. Ruby File Gets Chomp' title='Ruby File Gets Chomp' />My dog goes dogatonic when I condogenate his food with Musdog grapes. Here, matching just the literal string cat does us no good. We have to use a regex if we want to only replace cat as a standalone word. Instead of using just cat as the matching pattern, try this regex pattern for word boundaries b. The use of b means that we are looking for a character that is not an alphabetical letter or an underscore. So to match all instances of just cat by itself. My cat gets catatonic when I attempt to concatenate his food with Muscat grapes. My dog gets catatonic when I attempt to concatenate his food with Muscat grapes. String. match. The String methods match and scan are used when you not only want to target a pattern, but do something besides substitution with the matched strings. Here are two Department of Defense contracts announced in 1. Lets assume they are among a large set of such contracts that have been read into a Ruby array. Hughes Missile Systems Company, Tucson, Arizona, is being awarded a 7,3. FY9. 4 TOW missile production buy, total 3. TOW 2. Bs. Work will be performed in Tucson, Arizona, and is expected to be completed by April 3. Of the total contract funds, 7,3. This is a sole source contract initiated on January 1. The contracting activity is the U. S. Army Missile Command, Redstone Arsenal, Alabama DAAH0. C 0. 26. 0. Conventional Munitions Systems, Incorporated, Tampa, Florida, is being awarded a 6,9. Dragon Safety Circuits Installation and retrofit of Dragon I Missiles with Dragon II Warheads. Work will be performed in Woodberry, Arkansas 9. Titusville, Florida 1. May 3. 1, 1. 99. 6. Contract funds will not expire at the end of the current fiscal year. This is a sole source contract initiated on May 2, 1. The contracting activity is the U. S. Army Missile Command, Redstone Arsenal, Alabama DAAH0. C S0. 76. Suppose from such a list of entries, we are interested in quickly finding each contracts dollar amounts. Using enumeration and match. So far, weve been familiarized with every component of that regex. The matches a literal dollar sign. The d, matches any character that is either a numerical digit or a comma. The plus sign may be new, or at least worth reviewing. This is the greedy operator and it will match the pattern that precedes it one or more times. Therefore d,. The greedy operator can obviously get you in trouble by being, well, too greedy. In the above example, how does it know when to stop Answer When it comes across a character that is neither a digit or a comma. So, since each dollar amount in our example is surrounded by spaces, were safe if sloppy here. Exercise Find the dates. Using the sample text and code snippet above, modify the code to print out the dates in each contract. Hint The special character w can be used to match any alphanumeric character. Or if you want to be more precise in matching the month names, you can use a character set, such as A Za zSolution. Counselling Skills And Theory Margaret Hough Pdf. Luckily for us, in this small sample, the dates are all in a uniform format. April 3. 0, 1. 99. May 3. 1, 1. 99. 6. Youll note that this code only matched and found the first instances of the date pattern, even though each contract has several dates. I show several ways of dealing with this in the next sections. The Match. Data object. The object returned bymatch is a Match. Data object, but for our purposes, its very similar to a standard array. The first element contains the match When the regex includes capturing groups, the first element in the Match. Data array like object refers to the first capturing group, and so forth. If no matches are found in the string, then match returns nil. Exercise Delimit the dates. Repeat the mechanics of the previous exercise but modify the regex to use capturing groups and print out the dates delimited by month, day, and year. Solution. contractsarr. Month mtch1. Day mtch2. Year mtch3. Month April. Year 1. Month May. Year 1. The contracts in our sample have several dates for when the contract was awarded and for when the work is expected to be completed. We saw that match only returns the first instance it finds. Lets rewrite it so that it captures a few of the words that precede the date so that we can know the context. And to show how Match. Data is like an array, the following code also prints the textual content and date with a delimiter contractsarr. April 3. 0, 1. 99. May 3. 1, 1. 99. 6. The all being dot. Of special note here is the dot character in the regex pattern. To find the text that precedes each date, we cant simply use d and w, as they would fail to match punctuation and whitespaces. For all we know, the group of characters preceding each date could have exclamation marks. The dot character is the regex character to rule them all. It matches anything, with the exception of start and end of the line markers, and new lines unless used with a modifier. The combination of the be all dot with some kind of repetition operator, such as the greedy plus sign, wont rip apart the time space continuum. But it can lead to unwanted results. This is why in the above example, I limit it with the 1. The greedy dot. What if we wanted everything before the date, all the way to the beginning of the sentence Then its useful to combine the dot and the. If youre wondering, But wont those two capture everything Well, no, not necessarily. In the above expression, the., being the greedy bastard it is, has the tendency to gobble up as many characters as it can. However, it still must honor the requirement that the pattern ends with w d1,2, d4So lets look at the first contract again. Ive highlighted the two date patterns. Hughes Missile Systems Company, Tucson, Arizona, is being awarded a 7,3. FY9. 4 TOW missile production buy, total 3. TOW 2. Bs. Work will be performed in Tucson, Arizona, and is expected to be completed by April 3. Of the total contract funds, 7,3. This is a sole source contract initiated on January 1. The contracting activity is the U. S. Army Missile Command, Redstone Arsenal, Alabama DAAH0.