Strings : Getting Stuff Done

1. Strings : Getting Stuff Done

2. Basic Recipes • Does this look like an email address?

3. Basic Recipes • Does this look like an email address? • Is there an @

4. What is that Warning??? • Ugly digression…

5. Basic Recipes • Does this string have a @ in it? • Happier compiler version

6. Char vs 1 char string • 'a' is not the same kind of thing as "a" Object Number

7. Char vs 1 char string • string.at(index) and string[index] give a char • No • Yes

8. Char vs 1 char string • All other string functions give string • Yes • No

9. Basic Recipes • Want to separate username and domain:

10. Basic Recipes • Method 2:

11. Basic Recipes • I want to replace a @ with #:

12. Basic Recipes • I want to replace a @ with #: • Shorter version Set one char in stringto new value… must be a char

13. Basic Recipes • I want to replace a @ with #: • Long version

14. Chopping • Generally easier to chop as you go:

15. Chopping • Finding both '-' and then chopping:

16. Looping • Finding all groups in string like:123-4324-23-34-…-234 • While there is another dash, find dash, print everything up to dash

17. Looping • By chopping parts off:

18. Looping • By moving start/end indexes:

19. Looping Characters • Process each character : • Loop from 0 to length - 1 Current position Current letter

20. Looping Characters • Backwards

21. Modifying as we go • Shift all chars by one: • Get current letter • Modify • Replace current letter with changed

22. Case Study Hex Conversion • Convert hex numbers to decimal: • Possible digits:0-9, A (10), B (11), C (12), D (13), E (14), F (15) • Place values powers of 16: 1 x 4096 + 2 x 256 + 14 x 16 + 9 x 1 = 4841 12E916 = 484110

23. Case Study Hex Conversion • Need to access each digit • Need to figure out its value • Need to keep track of what place we are in • Need to build up a total

24. Case Study Hex Conversion • Need to access each digit • Need to figure out its value • char '4' != 4 • But '4' – '0' = 4

25. Case Study Hex Conversion • Need to access each digit • Need to figure out its value • Need to keep track of what place we are in • Each column is 16 x bigger than one to right • Need to build up a total