1 ENGI 2420 Structured Programming (Lab Tutorial 5) Memorial University of Newfoundland

ENGI 2420 – Structured Programming Lab Tutorial 5 2 Assignment 4 -- Style  Readability –No or incorrect indentation. –Poor choice of names  Too many redundant parentheses Too many parentheses hurt readability sum = ((sum)+((sign)*(power(x,i)/factorial(i))) ; A few redundant parentheses can reinforce precedence rules. This is fine. sum = sum + (sign * power(x,i) * factorial(i)) ; Spacing reinforces precedence rules. Also fine. sum = sum + sign*power(x,i)*factorial(i) ;  Unneeded if statements  Variables declared before loop rather than in the loop.  Comments –No documentation of local variables. –No function header comments

ENGI 2420 – Structured Programming Lab Tutorial 5 3 Assignment 4 -- Correctness  Compilation –Failing to declare a function before it is used.  Bugs –Summing the wrong number of terms –Failing to initialize variables before they are used. –Make a habit of declaring variables only when they are ready to be initialized. –Incorrect factorial calculation. –Infinite loops.

ENGI 2420 – Structured Programming Lab Tutorial 5 4 Assignment 4 -- Copying  Many assignments were copied  We will be dealing with these cases  The effect was plainly visible on the midterm.  Doing the assignments is integral to understanding the material,  which (if you need further motivation) is important come exam time.

ENGI 2420 – Structured Programming Lab Tutorial 5 5 Assignment-5  Structure of C++ files - assign5.h: contains the declarations for the functions - assign5.cpp: contains your implemented functions (submit this one via web-submit) - your own test code in a separate.cpp file (do NOT submit your test code)  Implement two functions as follows

ENGI 2420 – Structured Programming Lab Tutorial 5 6 Function 1  bool lineParameters(double x1, double y1, double x2, double y2, double& a, double& b)  Given the (x,y) coordinates of two points, find the parameters, a and b for the equation of a line, y = a*x + b, going through the two points, if possible (using the slope and y-intercept approach)  If the line can't be represented in this form then the function should return false, otherwise it should return true.  Must define and call at least two additional functions to i) compute the slope of the line connecting the points and ii) find the y-intercept of the line given its slope and a point on the line.

ENGI 2420 – Structured Programming Lab Tutorial 5 7 Execution Example (I)  (0.0, 0.0) and (10.0, 10.0) will return true –and give 1.0*x  (3.0, 3.0) and (6.0, 4.0) will return true –and give 0.333*x  (3.0,3.0) and (3.0, 4.0) will give a false result –there is no need to assign to the a and b parameters

ENGI 2420 – Structured Programming Lab Tutorial 5 8 Function 2  double outstandingDebt (double principle, double interestRate, double payment, int periods)  Returns the amount that will be outstanding on a loan after periods payments of $payment have been made, assuming that the original loan amount was $principle and that the interest rate per period is interestRate, as a decimal (i.e., 0.05 represents a rate of 5%)  Interest should be computed once per period and added to the principle before the payment is deducted  Use loops to do the calculation iteratively

ENGI 2420 – Structured Programming Lab Tutorial 5 9 Execution Example (II) outstandingDebt (100.00, 0.10, 20.0, 3) Periods passedDebt

ENGI 2420 – Structured Programming Lab Tutorial 5 10 Top-down design & bottom-up testing  Top down design –First I pseudo code lineParameters –As I write lineParameters I specify its auxiliary functions. –Then I write the auxiliary functions  Bottom up testing –First I test functions that call no others –I only test a function once I am certain all functions it calls are working.