More Loops

These first few are from chapter 3, but we skipped them.

size_t find(string pattern [, size_t pos=0]

This is a string class member function
size_t is a user defined type
- Defined by the people who implemented the string function.
- Probably an unsigned integer.
- But we can treat it as an int, with the compiler only occasionally complaining.
- In which case, a cast will take care of things.
In strings, positions start at 0.
It searches the string for a pattern starting at the given position
The position is optional, and assumed to be 0 if not given.
If the pattern is not found string::npos is returned.

Write a program to find the number of times a word occurs in a string. (i.e. how many times does "Dan" appear in "Danger, Danger, Danger!"

string substr(size_t pos, size_t lend)

This is another string member function.
It will extract a substring from a string.
We could write this if we wanted to but...
pos is where to start extracting the substring.
- pos starts at 0
len is the length of the substring to extract.
- len can be longer than the length of the string.
- In this case, it returns from the start position to the end of the string.
Write a program to read in a list of words, separated by commas print the individual word without the commas.

And a non-string function or two.

int rand()
Generate a random number between [0, RAND_MAX]
You need #include < cstdlib>
This is not a true random number, it is a pseudo-random number
- The same sequence is always produced.
- r_i = f(r_i-1)
- Try this.
We can change the starting point of the sequence with srand(int seed)
- YOU ONLY CALL srand ONCE PER PROGRAM.
- srand(5) will give a different default sequence.
- This is useful for debugging programs which involve randomness, you eliminate the real randomness.
- srand(time(NULL)) is good for random programs

Write a program that prints 5 random numbers between 1 and 6 (rolls a six sided die five times)

Write a program that emulates a magic 8 ball. The user types a question, the magic 8 ball repeats the question and provides an answer.

Do you understand the problem?
- In the traditional 8 ball, there are 5 negative, 5 neutral and 10 positive answers.
Algorithm?
Test Cases? - probably not.
eightBall.cpp