Recitation 6
Monday, October 6, 2014

Functions
•What is a general Function?
•
Points from each member of
A
to a member of
B
•
C
an’t have one
A
pointing to more than one
B
•
One to many is
NOT
allowed
•
More than one
A
can point to the same
B
•
Many to one is allowed

Is this a Function?
A
B
C
D
E
1
2
3
4
5
Yes!

Is this a Function?
A
B
C
D
E
1
2
3
4
5
Yes!

Is this a Function?
A
B
C
D
E
1
2
3
4
5
No!

Injective or One-to-One
•
Means that every member of
A
has its own (unique) matching
member in
B
•
One to Many is
NOT
allowed since it is also a function
•
Also Many to One is
NOT
allowed in this situation
•
You can have a
B
w/o a matching
A

Is this One to One?
A
B
C
D
E
1
2
3
4
5
Yes!

Is this One to One?
A
B
C
D
E
1
2
3
4
5
No!

Is this One to One?
A
B
C
D
E
1
2
3
4
5
6
Yes!

Surjective or Onto
•
Means that every
B
has at least one matching
A
•
Can be more than one
•
There won’t be a
B
left out

Is this Onto?
A
B
C
D
E
1
2
3
4
5
Yes!

Is this Onto?
A
B
C
D
E
1
2
3
4
Yes!

Is this Onto?
A
B
C
D
E
1
2
3
4
5
6
No!

Bijective
•