Strings : Getting Stuff Done

Basic Recipes

• Does this look like an email address?

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b o b @ a . c o m

Basic Recipes

• Does this look like an email address?– Is there an @

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b o b @ a . c o m

What is that Warning???

• Ugly digression…

Basic Recipes

• Does this string have a @ in it?– Happier compiler version

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b o b @ a . c o m

Char vs 1 char string

• 'a' is not the same kind of thing as "a"

Number Object

Char vs 1 char string

• string.at(index) and string[index] give a char

• No

• Yes

Char vs 1 char string

• All other string functions give string

• Yes

• No

Basic Recipes

• Want to separate username and domain:

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b o b @ a . c o m

Basic Recipes

• Method 2:

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b o b @ a . c o m

Basic Recipes

• I want to replace a @ with #:

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b o b @ a . c o m

Basic Recipes

• I want to replace a @ with #:– Shorter version

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b o b @ a . c o m

Set one char in stringto new value… must be a char

Basic Recipes

• I want to replace a @ with #:– Long version

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b o b @ a . c o m

Chopping

• Generally easier to chop as you go:

Chopping

• Finding both '-' and then chopping:

Looping

• Finding all groups in string like:123-4324-23-34-…-234

• While there is another dash, find dash, print everything up to dash

Looping

• By chopping parts off:

Looping

• By moving start/end indexes:

Looping Characters

• Process each character : – Loop from 0 to length - 1

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b o b @ a . c o m

Current positionCurrent letter

Looping Characters

• Backwards

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b o b @ a . c o m

Modifying as we go

• Shift all chars by one:– Get current letter–Modify– Replace current letter with changed

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 = 484112E916 = 484110

4096’s163

256’s162

16’s161

1’s160

1 2 E 9

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

4096’s163

256’s162

16’s161

1’s160

1 2 E 9

Case Study Hex Conversion

• Need to access each digit• Need to figure out its value– char '4' != 4– But '4' – '0' = 4

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

4096’s163

256’s162

16’s161

1’s160

1 2 E 9