WORKED EXAMPLE 7.1. Producing a Mass Mailing. We want to automate the process of producing mass mailings. A typical letter might look as follows:

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1 Worked Example 7.1 Producig a Mass Mailig 1 WORKED EXAMPLE 7.1 Producig a Mass Mailig We wat to automate the process of producig mass mailigs. A typical letter might look as follows: To: Ms. Sally Smith 123 Mai Street Aytow, NY Dear Ms. Smith: The Smith family may be the lucky wier i the C++ sweepstakes. Would't it be excitig if you were the first Aytow residets to use ACME's ew C++ developmet eviromet? etc. etc. Aother letter with the same template but differet values for the variable parts would look like this: To: Mr. Harry Morga 456 Park Ave Everyville, KS Dear Mr. Morga: The Morga family may be the lucky wier i the C++ sweepstakes. Would't it be excitig if you were the first Everyville residets to use ACME's ew C++ developmet eviromet? etc. etc. To set up such a mailig, we start with a template strig i which each of the variable parts is deoted by a digit 0 9. (We assume that digits are ot otherwise used i the template text.) To: , 5 6 Dear 0 2: The 2 family may be the lucky wier i the C++ sweepstakes. Would't it be excitig if you were the first 4 residets to use ACME's ew C++ developmet eviromet? etc. etc. This template is set up i a strig, like this: char letter_template[] = "To: 0 1 2\3\4, 5 6\\Dear 0 2: \\" "The 2 family may be the lucky wier i the C++ sweepstakes.\" "Would't it be excitig if you were the first 4 residets\" "to use ACME's ew C++ developmet eviromet? etc. etc. \\\"; (To declare a literal strig i C++ that does ot fit o a sigle lie, you write a sequece of literal strigs. The compiler combies them ito a sigle strig.)

2 2 C++ for Everyoe CHAPTER 7 Of course, we could produce a separate strig for each mailig, by replacig the digits with the values for a particular recipiet. But there is a more efficiet way. Your task will be to set up a vector of character poiters that poit to successive fragmets of the letter, either from the template strig or the variable parts. For example, the body of the letter above is represeted by poiters to the followig strigs: ": \\The " Variable 2 " family may be were the first " Variable 4 " residets " The variable parts are stored i a two-dimesioal array of characters. char variable_parts[10][var_length]; Each row of this array cotais a variable: strcpy(variable_parts[0], "Ms."); strcpy(variable_parts[1], "Sally"); strcpy(variable_parts[2], "Smith"); strcpy(variable_parts[3], "123 Mai Street"); strcpy(variable_parts[4], "Aytow"); strcpy(variable_parts[5], "NY"); strcpy(variable_parts[6], "12345"); Pritig a letter is achieved with the followig loop: vector<char*> fragmets = prepare_mailig(letter_template, variable_parts); Your task will be to implemet the prepare_mailig fuctio, ad to produce a mai fuctio that prits the two letters give above. Step 1 Draw a picture. We start with the data that is beig accessed through poiters: the strigs i the letter template (after replacig the variable placeholders with ull termiators), ad the strigs i the variable array. : \ \ T h e \0 f a m i l y f i r s t \0 r e s i d e M s. \0 S a l l y \0 S m i t h \ M a A y t o w i \0 S t r e e t \0 [0] [1] [2] [3] [4]

3 Worked Example 7.1 Producig a Mass Mailig 3 The poiters poit ito the template ad variable strigs, like this: : \ \ T h e \0 f a m i l y f i r s t \0 r e fragmets = M s. \0 S a l l y \0 S m i t h \ A y t M o a w i \0 S t r e e t \0 [0] [1] [2] [3] [4] Step 2 Declare poiter variables. We collect a sequece of char* poiters of ukow legth. Therefore, we use a vector of poiters vector<char*> fragmets; Step 3 Iitialize the poiters with variable addresses or heap memory. This is the task of the prepare_mailig fuctio. That fuctio eeds to sca the letter template for variable idicators, replace them with ull termiators, ad store poiters i the fragmets vector. Here is the pseudocode: Set the fragmet start to the begiig of the letter template. For each character i the letter template. If the character is a digit Add the fragmet start to the fragmets vector. Add the row of the variable deoted by the digit to the fragmets vector. Replace the digit with a ull termiator. Set the fragmet start to the followig character. You will fid the C++ code i the code listig below. Step 4 Use the * or [] operator to access your data. This step has already bee completed i the problem statemet. It was a requiremet that the fragmets ca be prited with the followig loop:

4 4 C++ for Everyoe CHAPTER 7 All that remais is to complete a mai program that prits two letters, as show i the code listig. Note that the prepare_mailig fuctio is oly called oce. Afterward, the variable array is updated for each mailig, but the fragmets vector ever chages. Here is the complete program, ch07/mail.cpp. #iclude <cctype> #iclude <iostream> #iclude <strig> #iclude <vector> usig amespace std; cost it VAR_LENGTH = 20; /** Prepares a letter template for a mass letter a strig with placeholders 0 9 (which will be replaced with ull vars a two-dimesioal array for holdig the variable parts of the a vector of fragmets, poitig alterately to strigs i the letter template ad i the variable array) */ vector<char*> prepare_mailig(char* letter, char vars[][var_length]) vector<char*> fragmets; char* fragmet_start = letter; for (char* p = letter; *p!= '\0'; p++) if (isdigit(*p)) fragmets.push_back(fragmet_start); fragmet_start = p + 1; it var_idex = *p - '0'; fragmets.push_back(vars[var_idex]); *p = '\0'; fragmets.push_back(fragmet_start); retur fragmets; it mai() char variable_parts[10][var_length]; strcpy(variable_parts[0], "Ms."); strcpy(variable_parts[1], "Sally"); strcpy(variable_parts[2], "Smith"); strcpy(variable_parts[3], "123 Mai Street"); strcpy(variable_parts[4], "Aytow");

5 Worked Example 7.1 Producig a Mass Mailig 5 strcpy(variable_parts[5], "NY"); strcpy(variable_parts[6], "12345"); char letter_template[] = "To: 0 1 2\3\4, 5 6\\Dear 0 2: \\" "The 2 family may be the lucky wier i the C++ sweepstakes.\" "Would't it be excitig if you were the first 4 residets\" "to use ACME's ew C++ developmet eviromet? etc. etc. \\\"; vector<char*> fragmets = prepare_mailig(letter_template, variable_parts); strcpy(variable_parts[0], "Mr."); strcpy(variable_parts[1], "Harry"); strcpy(variable_parts[2], "Morga"); strcpy(variable_parts[3], "456 Park Ave"); strcpy(variable_parts[4], "Everyville"); strcpy(variable_parts[5], "KS"); strcpy(variable_parts[6], "67890"); retur 0;