[Solved] CS135 Project1-Streams and calculators

We have learned how to read user input from keyboard, and we will learn how to use file streams toread data from files.However, there is another simpler way to read data from a file using a feature of Unix shell calledstandard input redirection. We are going to use it in this assignment.In Unix, if we run the program as follows:./program < myfile.txtEvery time you read from cin , such as in this statementcin >>

In Unix, if we run the program as follows:./program < myfile.txtEvery time you read from cin , such as in this statementcin >> x;the value x is read not from the keyboard, but from the text file myfile.txt you specified. Isntit neat? It is called file redirection. The text from the file is redirected character by character as thestandard input for your program.To read the full contents of the file word by word, you can write a program:#include <iostream>using namespace std;int main() {string s;while(cin >> s) { // While the reading operation is a successcout << s << endl; // print the read word}}It relies on the fact that the expression cin >> s does not only read a string into the variable s ,but also itself evaluates to true , if the reading operation was a success, and to false , if it wasa failure. Practically, it means that when the program reaches the end of the file, the operationcin >> s fails to read anything from the file, evaluating to false and indicating that the loopshould stop.Task A. Adding integers.Write a program sum.cpp that reads a sequence of integers from cin , and reports their sum.ExampleIf you have a file numbers.txt that contains:10 15 16 -7 102 345then if you redirect it into the program, it should report:$ ./sum < numbers.txt481Task B.Calc: A calculator program.We want to make a simple calculator that can add and subtract integers, and will acceptarbitrarily long mathematical formulas composed of symbols + , , and non-negative integernumbers.Imagine you have a file formula.txt with the summation formula such as:100 + 50 25 + 0 + 123 1If you redirect the file into your program, it should compute and print the answer:$ ./calc < formula.txt247It may sound tricky, but it is actually easy to write such a program, and you already know all theneeded tools. Just think carefully how to put it all together.Specifically, write a program calc.cpp that reads from the cin a sequence of one or morenon-negative integers written to be added or subtracted. Space characters can be anywhere in theinput. After the input ends (end-of-file is reached), the program should compute and print the result ofthe input summation.Possible input for your program may look like this:1510 + 3 + 0 + 255+6- 7 -8 + 9 + 10 111 + 1 + 1 + 1 +1 + 1 + 1 + 1 +1 + 1 + 1 + 1 +1 + 1 + 1 + 1(Each of the inputs above is a separate file containing one single formula, even if it spans multiplelines.)The corresponding outputs should be: 15 , 38 , 4 , and 16 .A hint on how to handle possible space characters in the input:You can use >> operator to read the numbers and the + / characters, because >> will beskipping all spaces between the input terms. It is also suggested to use the char type for readingthe + / operator characters, not string , because it will work well even when numbers andthe operator symbol are adjacent and not separated by spaces (such as in 10+5+3 ).Task C. Calc2: Reading multiple formulas.Write a better version of the calculator, calc2.cpp , that can evaluate multiple arithmeticexpressions. Lets use the semicolon symbol that must be used at the end of each expression in theinput.Assuming that the input file formulas.txt looks as follows:15 ;10 + 3 + 0 + 25 ;5 + 6 7 8 + 9 + 10 11 ;When we run the program with that input, the output should evaluate all of the expressions and printthem each on its own line:$ ./calc2 < formulas.txt15384Task D. Calc3: Squares.Write an even better calculator program calc3.cpp that can understand squared numbers. Weare going to use a simplified notation X^ to mean X . For example, 10^ + 7 51^ shouldmean 10 + 7 51 .Example:When reading input file formulas.txt5^;1000 + 6^ 5^ + 1;the program should report:22 2$ ./calc3 < formulas.txt251012A hint:To take into account ^ , dont add or subtract new numbers right away after reading them. Instead,remember the number, read the next operator and if it is a ^ , square the remembered number, thenadd or subtract it.An additional note on how to test calculator programsIn addition to writing your formulas into files, remember that your program still accepts the input fromthe keyboard (Hey, do you see the benefit of input redirection? The program can work great on bothkeyboard and file inputs!)When typing the input from the keyboard, the key combination Ctrl+D emulates the End-of-filesituation, telling the program that the input has ended.So, you can test your program like this:$ ./calc15 4 + 13 2 + 1 <Enter> <Ctrl+D>23(finalizing your input by pressing Enter and Ctrl+D ).