©LPU CSE101 C Programming
CSE101-Lec#13
•
Math Library functions
©LPU CSE101 C Programming
Functions in Mathematics
“A relationship between two variables, typically
x
and
y
, is
called a
function
, if there is a
rule
that assigns to each
value of
x
one and only one value of
y
.”
So, for example, if we have a function
f
(
x
) =
x
+ 1
then we know that
f
(-2.5)
=
-2.5
+
1
=
-1.5
f
(-2)
=
-2
+
1
=
-1
f
(-1)
=
-1
+
1
=
0
f
(0)
=
0
+
1
=
+1
f
(+1)
=
+1
+
1
=
+2
f
(+2)
=
+2
+
1
=
+3
f
(+2.5)
=
+2.5
+
1
=
+3.5
…
©LPU CSE101 C Programming
Functions in Mathematics
Likewise, if we have a function
a
(
y
) = |
y
|
then we know that
…
a
(-2.5) = | -2.5
| = +2.5
a
(-2) = | -2
| = +2
a
(-1) = | -1
| = +1
a
(0) = | 0
| =
0
a
(+1) = | +1
| = +1
a
(+2) = | +2
| = +2
a
(+2.5) = | +2.5 | = +2.5
…
©LPU CSE101 C Programming
Function Argument
f
(
x
) =
x
+ 1
a
(
y
) = |
y
|
We refer to the thing inside the parentheses
immediately after the name of the function as
the
argument
(also known as the
parameter
)
of the function.
In the examples above:
•
the argument of the function named
f
is
x
;
•
the argument of the function named
a
is
y
.
©LPU CSE101 C Programming
Absolute Value Function in C
•
The
abs
function calculates the
absolute
value
of its argument. It’s the C analogue of
the mathematical function
a(
y
) = |
y
|
(the absolute value function)
a= abs(y);
©LPU CSE101 C Programming
Absolute Value Function in C
…
fabs(-2.5)
returns
2.5
abs(-2)
returns
2
abs(-1)
returns
1
abs(0)
returns
0
abs(1)
returns
1
abs(2)
returns
2
fabs(2.5)
returns
2.5
…
©LPU CSE101 C Programming
Absolute Value Function in C #3
We say “
abs
of -2
evaluates to
2” or “
abs
of -2
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- Fall '14
- gauravtak
- C Programming, fabs, math library functions
