7- predefined functions (library functions)

Question 1

Function

Answer 1

named group of statements carrying out a particular task that accepts values and computes the result

Question 2

Function name

Answer 2

identifier distinguishing the function from others
example – square root function: sqrt

Question 3

argument

Answer 3

the value accepted by the function to use in computation

Question 4

return value

Answer 4

value computed by the function

Question 5

function call (function invocation)

Answer 5

executing function code from elsewhere in program
syntax: expression consisting of function name followed by arguments in parentheses
result = sqrt(9.0);
semantics: argument is evaluated, function is executed, return value replaces function invocation
invocation forms
in expression – return value replaces invocation in expression evaluation
result = sqrt(9.0) – myVar5;
standalone – return value is ignored
srand(55);
argument variants
function may have more than one argument
result = pow(myVar, 55);
an argument is an (arbitrary) expression
result = sqrt(myVar2 + 9.0);
nested function call: use of one function call as argument to another
result = sqrt(abs(myVar));

Question 6

casting

Answer 6

explicit type conversion

Question 7

coercion

Answer 7

implicit type conversion

Question 8

Random number generation

Answer 8

(pseudo) random number generation pre-defined functions are used to create events unpredictable by user (e.g. events in games)
need to include <cstdlib>
generates a series of numbers, numbers within single series are (pseudo) random</cstdlib>

Question 9

srand(seed)

Answer 9

initializes random number generator, needs to be invoked once in the program, no return value

Question 10

seed

Answer 10

integer, selects the (pseudo) random series

Question 11

rand()

Answer 11

returns a new integer random number in the series, can be used multiple times in program, no argument

Question 12

time(nullptr)

Answer 12

returns number of seconds since 01/01/1970, good for initializing unique series, needs <ctime>
nullptr is there for historical reasons</ctime>

Question 13

srand(1);

Answer 13

repeats series every time you run your program – good for debugging

Question 14

srand(time(nullptr));

Answer 14

selects unpredictable series every time you run your program – good for final compilation