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Subject: Operators - C# Nuts and Bolt - Beta2
Date: Wed, 29 Aug 2007 13:28:55 +0800
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<P class=3DMsoNormal><IMG id=3D_x0000_i1025 height=3D48=20
src=3D"http://www.vijaymukhi.com/documents/books/csadv/bpb.jpg" =
width=3D64></P>
<P class=3DMsoNormal><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></P>
<P class=3DMsoNormal><SPAN=20
style=3D"FONT-SIZE: 15pt; COLOR: black; FONT-FAMILY: Garamond">Chapter=20
7</SPAN></P>
<P class=3DMsoNormal><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></P>
<P class=3DMsoNormal><SPAN=20
style=3D"FONT-SIZE: 26pt; COLOR: black; FONT-FAMILY: =
Garamond">Operators</SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext">We all like to =
express ourselves=20
in different ways. Some smile, some laugh, some screech and some even =
shout. The=20
C# programming language lays a lot of emphasis on expressions and has =
one of the=20
largest chapters in its documentation devoted to it. An expression is a =
sequence=20
of operators and operands providing some computational activity.=20
<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext">An expression can be =
built in n=20
number of ways. It can be as simple as a value resulting in a certain =
type. It=20
can also consist of a variable with a type. A namespace can also occur =
in an=20
expression but it must be only at the beginning. A type like a namespace =
can=20
also occur on the left hand side of an expression. The usual gang of =
idiots like=20
properties, indexers, properties can also be included in an expression. =
However,=20
the final result of an expression can never ever be a namespace, type, =
method=20
group or event access. These can only occur in intermediate results.=20
<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext">Expressions are not =
conjured out=20
of thin air but are made up of only two entities, operators and what we =
offer=20
them in homage, operands. Operands can include constants, variables, =
indexers=20
etc. The second entity, operators is what this chapter is dedicated=20
to.<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCbase><B><SPAN=20
style=3D"FONT-SIZE: 14pt; COLOR: windowtext; FONT-FAMILY: Tahoma"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></B></P>
<P class=3DCbase><B><SPAN=20
style=3D"FONT-SIZE: 14pt; COLOR: windowtext; FONT-FAMILY: =
Tahoma">Checked and=20
Unchecked Operators<o:p></o:p></SPAN></B></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCprg><U>a.cs</U><o:p></o:p></P>
<P class=3DCprg>class zzz<o:p></o:p></P>
<P class=3DCprg>{<o:p></o:p></P>
<P class=3DCprg>byte i =3D 255;<o:p></o:p></P>
<P class=3DCprg>byte j =3D 256;<o:p></o:p></P>
<P class=3DCprg>public static void Main()<o:p></o:p></P>
<P class=3DCprg>{<o:p></o:p></P>
<P class=3DCprg>byte k =3D -1;<o:p></o:p></P>
<P class=3DCprg>}<o:p></o:p></P>
<P class=3DCprg>}<o:p></o:p></P>
<P class=3DCprg><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></P>
<P class=3DCoutput><U>Compiler Error</U><o:p></o:p></P>
<P class=3DCoutput>a.cs(7,10): error CS0031: Constant value '-1' cannot =
be=20
converted to a 'byte'<o:p></o:p></P>
<P class=3DCoutput>a.cs(4,10): error CS0031: Constant value '256' cannot =
be=20
converted to a 'byte'<o:p></o:p></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext">A byte can only store =
values from=20
0 to 255. We have initialized i to the largest possible value a byte can =
store=20
i.e. 255. For the second variable, we try and go beyond the range that a =
byte=20
can handle. Well, the compiler comes back screaming at us with an error. =
This is=20
the behaviour in the case of variable j. This is enough proof that the =
compiler=20
checks the values, the variables are being initialized to. For that =
matter, it=20
could be a local variable created in a function or an instance variable =
created=20
out of a function. Come what may, C# does not allow you to take a byte =
and give=20
it a value falling outside its range of 0 to 255.<o:p></o:p></SPAN></P>
<P class=3DCbase><SPAN style=3D"COLOR: windowtext"><![if =
!supportEmptyParas]><![endif]>&nbsp;<o:p></o:p></SPAN></P>
<P class=3DCprg><U>a.cs</U><o:p></o:p></P>
<P class=3DCprg>class zzz<o:p></o:p></P>
<P class=3DCprg>{<o:p></o:p></P>
<P class=3DCprg>public static void Main() <o:p></o:p></P>
<P class=3DCprg>{<o:p></o:p></P>
<P class=3DCprg>byte k =3D (byte)256;<o:p></o:p></P>
<P class=3DCprg>byte l =3D (byte)257;<o:p></o:p></P>
<P class=3DCprg>byte m =3D (byte)514;<o:p></o:p></P>
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