Prestwood IT: Comparison Operators (Cross Reference Coding Encyclopedia: ASP Classic)

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Comparison Operators

General Info: Round Floating Point Numbers

When comparing floating point numbers, make sure you round to an acceptable level of rounding for the type of application you are using.

Languages Focus

A comparison operator compares two values either literals as in "Hello" and 3 or variables as in X and Counter. Most languages use the same operators for comparing both numbers and strings. Perl, for example, uses separate sets of comparison operators for numbers and strings.

ASP Classic: =, <>

Save as VB Classic. Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does ASP evaluate the math correctly? No!

If .1 + .1 + .1 = .3 Then
  Response.Write "correct"
Else
  Response.Write "not correct"
End If

ASP Classic Comparison Operators (=, <>)

Cross Reference Examples:

Access VBA: =, <>

Save as VB Classic. Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does Access evaluate the math correctly? No!

If 0.1 + 0.1 + 0.1 = 0.3 Then
  MsgBox "correct"
Else
  MsgBox "not correct"
End If

C#: ==, !=

Common comparison operators:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does C# evaluate the math correctly? No!

if (.1 + .1 + .1 == .3)
  MessageBox.Show("correct");
else
  MessageBox.Show("not correct");

C++: ==, !=

Common comparison operators:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//C++Builder example (ShowMessage is a VCL method).

//Does C++Builder evaluate the math correctly? No!

If (.1 + .1 + .1 == .3)
  ShowMessage("correct");
else
  ShowMessage("not correct");

C++/CLI: ==, !=

Same as standard C++. Common comparison operators:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does C++/CLI evaluate the math correctly? No!

if (0.1 + 0.1 + 0.1 == 0.3)
  MessageBox::Show("correct");
else
  MessageBox::Show("not correct");

Corel Paradox: =, <>

Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

'Does ObjectPAL evaluate the math correctly? No!

If .1 + .1 + .1 = .3 Then
  msgInfo("", "correct")
Else
  msgInfo("", "not correct")
endIf

ObjectPAL Comparison Operators (=, <>)

Delphi: =, <>

Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does Delphi evaluate the math correctly? Yes!

//Refer to math.pas MaxSingle for more info.

if (0.1 + 0.1 + 0.1 = 0.3) then
  ShowMessage('correct')
else
  ShowMessage('not correct')

Delphi Comparison Operators (=, <>)

Delphi Prism: =, <>

Same as Delphi. Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does Prism evaluate the math correctly? No!

//This is different than later versions of

//Delphi that muse MaxSingle in math.pas.

If .1 + .1 + .1 = .3 Then
  MessageBox.Show("correct")
Else
  MessageBox.Show("not correct");

Java: ==, !=

The Java comparison operators are:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

More Info / Comment

JavaScript: ==, !=

Common comparison operators:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does JavaScript evaluate the math correctly? No!

if (.1 + .1 + .1 == .3) {
  document.write("correct");
}
else {
  document.write("not correct");
}

Perl: ==, !=

Common comparison operators:

==	equal
!=	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Perl also offers additional string comparison operators:

eq	string equals
ne	string not equal
lt	string less than
gt	string greater than
le	string less than or equal
ge	string greater than or equal

Syntax Example:

#Does Perl evaluate the math correctly? No!

if ((.1 + .1 + .1) == .3) {
  print("Correct<br>");
} else {
  print("Not correct<br>");
}

PHP: ==, != or <>

Common comparison operators:

==	equal
!= or <>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

PHP 4 and above also offers === for indentical (equal plus same type) and !== for not identical (not equal or not same type).

Syntax Example:

//Does PHP evaluate the math correctly? No!

if (.1 + .1 + .1 == .3) {
  echo "correct";
}
else {
  echo "not correct";
}

VB Classic: =, <>

Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example:

//Does VB evaluate the math correctly? No!

If 0.1 + 0.1 + 0.1 = 0.3 Then
  MsgBox "correct"
Else
  MsgBox "not correct"
End If

VB.Net: =, <>

Save as VB Classic. Common comparison operators:

=	equal
<>	not equal
<	less than
>	greater than
<=	less than or equal
>=	greater than or equal

Syntax Example: 1 certification question.

//Does VB.Net evaluate the math correctly? No!

If 0.1 + 0.1 + 0.1 = 0.3 Then
  MessageBox.Show("correct")
Else
  MessageBox.Show("not correct")
End If