ECE15: Homework 10. void wordstats(file *fp, char string[]) { void printfrequencies(file *fp) {

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1 ECE15: Homework 10 Recall that in the Unix dialogues shown below, we denote the prompt by ( )$ and show user input in red and computer output in black. We indicate a single space by in computer output, and by in user input. You can assume that the user will enter valid inputs. For this homework you will need to create two additional files: myheader.h containing the declarations of the functions you will use for all three homework problems, and myfunctions.c containing the definitions of the functions you will use for all three problems. Each of your three programs will start with #include "myheader.h" and will contain only main and no other function. Each program (say xyz.c) will have to be compiled as gcc xyz.c myfunctions.c. To get you started, here is the myheader.h file you need to use, and a skeleton of the myfunctions.c file you need to write. To copy them to your directory, type cp -r /../public/hw8/ / (The myheader.h file in public also includes a definition of M PI in case you don t have it.) // This is your myheader.h file, you can cut and paste (or copy) it. // Declarations for sortfile.c void sort(int array[], int length); // Declarations for statistics.c void lowercasestring(char string[]); void wordstats(file *fp, char string[]); void printfrequencies(file *fp); // Declarations for car-pol.c void car2pol(double x, double y, double *pr, double *ptheta); void pol2car(double r, double theta, double *px, double *py); // This is a skeleton for your myfunctions.c file // Functions for sortfile.c void sort(int array[], int length) { enter body } // Functions for statistics.c int letterfrequencies[26]; // Global array for wordstats, printfrequencies void lowercasestring(char string[]) { enter body } void wordstats(file *fp, char string[]) { enter body, use letterfrequencies[], use a static variable } void printfrequencies(file *fp) { enter body, use letterfrequencies[] } // Functions for car-pol.c void car2pol(double x, double y, double *pr, double *ptheta) { enter body } void pol2car(double r, double theta, double *px, double *py) { enter body }

2 Problem 1. Write a program sortfile.c that takes as command line arguments an input file name, an output file name, and an optional third argument indicating the largest number of integers to sort. The program opens the input file consisting of at most 50 integers, sorts them in increasing order, and prints the sorted sequence to the output file. If the optional argument exists, let s call it k, then if k is smaller than the number of integers in the input file, only the first k integers in the input file will be sorted and printed to the output file. You can assume that the input file exists and has the right format. ( )$ more input ( )$ a.out input1 output1.1 ( )$ more output ( )$ a.out input1 output1.2 5 ( )$ more output ( )$ more input ( )$ a.out input2 output2.1 ( )$ more output ( )$ a.out input2 output ( )$ more output ( )$ a.out input2 output2.3 0 ( )$ more output2.3 ( )$ more input3 ( )$ a.out input3 output3 ( )$ more output3 ( )$ The program must call the following functions that you will define in myfunctions.c. void sort(int array[], int length) sorts the first length elements of array in increasing order. For example, if array is { } and length is 3, then sort will modify array to { }. You can assume that length will be at most the size of array. The file sortfile.c will consist of only just main defined and functioning as follows. int main(int argc, char *argv[]) opens input file argv[1], calls sort to sort its elements, and prints the sorted elements in the output file argv[2]. If argv[3] exists, then it is a an integer k. If k is smaller than the number of elements in the input file, then only the first k elements will be sorted and printed in the output file. 2

3 Problem 2. This program provides practice with global and static variables. In real-life programming you may choose to define these variables differently. Write a program statistics.c that takes as command-line arguments a sequence of words, and then asks the user for the name of an output file. The program prints in the file the lowercase form of each word, its length, and the cumulative length so far. After doing that for all words, the program prints each letter of the alphabet that was included in these words followed by the number of times the letter appeared. You may assume that the user will type only letters (no punctuations or numbers). ( )$ a.out Peter Piper picked a peck Output file: output1 ( )$ more output1 peter: length=5 total=5 piper: length=5 total=10 picked: length=6 total=16 a: length=1 total=17 peck: length=4 total=21 Letters: a:1 c:2 d:1 e:5 i:2 k:2 p:5 r:2 t:1 ( )$ a.out abracadabra Output file: output2 ( )$ more output2 abracadabra: length=11 total=11 Letters: a:5 b:2 c:1 d:1 r:2 ( )$ a.out Output file: output3 ( )$ more output3 Letters: ( )$ The program should use the following variables: int letterfrequencies[26] a global array that tracks the number of times each letter has appeared so far. It will be used by the functions wordstats and printfrequencies. This variable is already defined for you in myfunctions.c static int cumulativelength a static variable defined inside the function wordstats that tracks the cumulative length of words so far. The program should include the following functions. Of these functions, main should be defined in statistics.c and all other functions should be defined in myfunctions.c void lowercasestring(char string[]) Converts all upper-case letters in string to lower case. You can use the same-named function you wrote for the previous homework. void wordstats(file *fp, char string[]) Prints everything below to the file pointed to by fp. Prints string. 3

4 Prints the length of string. You can determine the length by using the function stringlen you wrote for the last homework or the function strlen defined in string.h. Updates and prints the static variable cumulativelength (see above) that tracks the cumulative word lengths so far. Updates a global array letterfrequencies (see above) that tracks the number of times each letter has appeared among the words processed so far. void printfrequencies(file *fp) Prints everything below to the output file pointed to by fp. Checks the global array letterfrequencies, and for each letter from a to z that appeared at least once, prints the number of times it appeared. int main(int argc, char *argv[]) Asks the user for the name of an output file, and opens the file. For each word in the command line, calls lowercasestring to convert uppercase letter to lower, and then wordstats to print the word and cumulative lengths in the file, and to update the number of times each letter appears. After all words are processed, calls printfrequencies to print the number of time each seen letter has appeared. 4

5 Problem 3. A 2-dimensional vector can be represented by its Cartesian coordinates (x, y) indicating its projections on the horizontal and vertical axes respectively, or by its polar coordinates (r, θ) indicating its distance from the origin and its angle from the horizontal axis respectively. See for example the following figure π 6 π (x,y) = ( 3,1) (r,θ) = (2, 5π 6 ) (x,y) = (1,1) (r,θ) = ( 2, π 4 ) Figure 1: Two vectors and their Cartesian and polar representations As is well known, polar coordinates can be converted to Cartesian via the transform x = r cosθ and y = r sinθ, and Cartesian coordinates can be converted to polar via the transform arctan(y/x) if x > 0, r = arctan(y/x) + π if x < 0, x 2 + y 2 and θ = π/2 if x = 0, y > 0, π/2 if x = 0, y < 0, 0 if x = 0, y = 0. Note that θ is expressed in radians, that the last three cases are provided to avoid division by 0, and that for (x,y) = (0,0) the angle θ does not matter, but we define it to be 0, and please do so too. Write a program car-pol.c that takes two command-line arguments: an input-file name and an output-file name. The input can be of two types: If it starts with the word Cartesian (so capitalized), then it will be followed by zero or more (x,y) pairs. The program should create an output file of the specified name that starts with the word Polar (so capitalized) and continues with the polar-coordinate equivalent of all original vectors. Conversely, if the input file start with the word Polar, then it will be followed zero or more (r,θ) pairs. The program should create an output file of the specified name that starts with Cartesian and continues with the Cartesian-coordinate equivalent of all original vectors. You can use the math.h functions cos, sin, and atan, but not atan2. In your code, have main read the command-line arguments and read and write the files. Declare the following functions in myheader.h and define them in myfunctions.c Your car-pol.c file should consist of just main and call the following functions that should be defined in myfunctions.c 5

6 void car2pol(double x, double y, double *pr, double *ptheta); converts Cartesian (x,y) to polar (r,θ) where pr and ptheta are pointers to r and θ void pol2car(double r, double theta, double *px, double *py); convert polar (r,θ) to Cartesian (x,y), where px and py are pointers to x and y. Your answers will be considered correct if they are within 0.01% (factor of 1 ± ) from those listed by test.sh. ( )$ more file1 Cartesian ( )$ a.out file1 file2 ( )$ more file2 Polar ( )$ a.out file2 file3 ( )$ more file3 Cartesian e e-05-3 ( )$ more file4 Cartesian ( )$ a.out file4 file5 ( )$ more file5 Polar ( )$ 6