Checking Whether
the Conversion of a String into a Floating-point Number is Possible:
isFloat() Function
The
isFloat() function is used to
check whether the conversion of a string into a floating-point number
is possible. The actual conversion should be done by the
parseFloat()
function, which will be
described in the next section.
The
syntax of isFloat() is shown
below:
Lang.isFloat(string);
isFloat()
returns true
if string can be
converted into the float type, otherwise it returns false.
If there are any errors or if the mobile device does not support
floating-point operations, the function returns invalid.
(Remember that the float()
function is used to check
whether a mobile device supports floating-point operations.)
The
following WMLScript example demonstrates how to use the isFloat()
function:
v
= Lang.isFloat(100);
w = Lang.isFloat("100");
x =
Lang.isFloat("100.999");
y =
Lang.isFloat("WMLScript Tutorial");
z =
Lang.isFloat(true);
After
executing the above script, the variables v
to x have the Boolean
value true while y
and z have the Boolean
value false.
Note
that the plus character (+), the
minus character (-), the dot character (.) and the letter e can
appear in string, like
this:
w
= Lang.isFloat("+100.999");
x =
Lang.isFloat("-100.999");
y =
Lang.isFloat("100.999e2");
z =
Lang.isFloat("100.999e-2");
After
executing the above script, the variables w
to z contain the
Boolean value true.
If
non-numeric characters other than the above four (+ - . e) is present
in string, the WMLScript interpreter will
see if the characters before the non-numeric character form a valid
floating-point value. If yes, the isFloat()
function will still return true.
Here is an example:
x
= Lang.isFloat("100.999abc");
y =
Lang.isFloat("100.999e-2abc");
After
executing the above script, both x
and y have the value
true.
Converting a String
to a Floating-point Number: parseFloat() Function
The
parseFloat() function is used
to convert a string to a floating-point number. Its syntax is:
Lang.parseFloat(string);
If
string cannot be converted to
the float type, the mobile device does not support floating-point
operations or an error occurs, parseFloat()
returns an invalid value. (Remember that the float()
function is used to check
whether a mobile device supports floating-point operations.)
The
following WMLScript examples demonstrate the behavior of the
parseFloat() function:
x
= Lang.parseFloat(100);
y = Lang.parseFloat("100");
After
the execution of the script, both x
and y have the
floating-point value 100.0.
x
= Lang.parseFloat("100.999");
y =
Lang.parseFloat("+100.999");
After
the execution of the script, both x
and y have the
floating-point value 100.999.
x
= Lang.parseFloat("-100.999");
After
the execution of the script, x
has the floating-point value -100.999.
x
= Lang.parseFloat("100.999e2");
y =
Lang.parseFloat("100.999e-2");
After
the execution of the script, x
has the floating-point value 10099.9 and y
has the floating-point value 1.00999.
x
= Lang.parseFloat("100.999abc");
y =
Lang.parseFloat("100.999e-2abc");
After
the execution of the script, x
has the floating-point value 100.999 and y
has the floating-point value 1.00999.
x
= Lang.parseFloat("WMLScript Tutorial");
y =
Lang.parseFloat(true);
After
the execution of the script, both x
and y have the invalid
value.
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