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| << D.7.0- String constants | AppendixD | D.9.0- Unsupported conversion functions >> |
Conversion Functions
Normally you don't need to convert values in VBScript, because there is only one data type, the Variant.
Implicit conversion is generally applied when needed, but when you pass a value to a non-variant procedure in a COM object that needs the value passed ByRef, you will have to pass the value with the precise data subtype. This can be done by placing the argument in it's own set of parentheses, which forces a temporary evaluation of the argument as an expression:
Dim objByRefSample
Dim intTest
' Initialize the variable
intTest = "5"
' Create the object
Set objByRefSample = CreateObject("MyObject.ByRefSample")
' Call the method
objByRefSample.PassIntegerByReference (intTest)
' Destroy the object
Set objByRefSample = Nothing
The PassIntegerByReference method is a VB sub-procedure with just one argument of type integer that is passed ByRef.
What happens is that the value 5 stored in the intTest variable is actually explicitly coerced into a variable of subtype Integer, so that it conforms to the methods argument type. If you remove the parentheses, you will get a runtime error, because the implicit coercion will treat the string value as a double.
This is just one way of solving the problem. Another way is to use the CInt conversion function (listed below) when calling the method.
At some point however, you might need to convert a value of one data subtype to another data subtype. This can be necessary for various reasons:
- You need to present a number in hexadecimal notation instead of decimal
- You need the corresponding character code for a character or vice versa
- You need to pass values to a non-variant property procedure or as a function parameter in a COM object
- You need to save data in a database
See Chapter 2 Variables and Data Types for an explanation of the different data types.
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Asc |
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Syntax
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Asc(string)
string is any valid string expression. |
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Note
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A runtime error occurs if string doesn't contain any characters. string is converted to a String subtype if it's a numeric subtype.
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Example |
intCharCode = Asc("WROX")
intCharCode now holds
the value 87, which is the ANSI
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See Also |
AscB, AscW, Chr, ChrB and ChrW |
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AscB |
Returns the ANSI character code for the first byte in a string containing byte data.
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Syntax
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AscB(string) string is any valid string expression.
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Note
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A runtime error occurs if string doesn't contain any characters. For normal ANSI strings this function will return the same as the Asc function. Only if the string is in Unicode format will it be different from Asc. Unicode characters are represented by two bytes as opposed to ANSI characters that only need one.
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Example |
intCharCode = AscB("WROX")
intCharCode now holds
the value 87, which is the ANSI
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See Also |
Asc, AscW, Chr, ChrB and ChrW |
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AscW |
Returns the Unicode character code for the first character in a string.
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Syntax
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AscW(string) string is any valid string expression.
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Note
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A runtime error occurs if string doesn't contain any characters. string is converted to a String subtype if it's a numeric subtype. For use on 32-bit Unicode enabled platforms only, to avoid conversion from Unicode to ANSI.
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Example |
intCharCode = AscW("WROX")
intCharCode now holds the value 87, which is the Unicode character code for "W".
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See Also |
Asc, AscB, Chr, ChrB and ChrW |
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CBool |
Returns a Boolean value (Variant subtype 11) corresponding to the value of an expression.
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Syntax
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CBool(expression) expression is any valid expression.
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Note
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A runtime error occurs if expression can't be evaluated to a numeric value. If expression evaluates to zero then false is returned; otherwise, true is returned.
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Example |
Dim intCounter,
blnValue blnValue = CBool(intCounter)
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See Also |
CByte, CCur, CDbl, CInt, CLng, CSng and CStr |
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CByte |
Returns an expression converted to Variant subtype Byte (17).
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Syntax
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CByte(expression) expression is any valid numeric expression.
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Note
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A runtime error occurs if expression can't be evaluated to a numeric value or if expression evaluates to a value outside the acceptable range for a Byte (0-255). Fractional values are rounded.
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Example |
Dim dblValue, bytValue dblValue = 5.456 bytValue = CByte(dblValue)
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See Also |
CBool, CCur, CDbl, CInt, CLng, CSng and CStr |
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CCur |
Returns an expression converted to Variant subtype Currency (6).
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Syntax
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CCur(expression) expression is any valid expression.
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Note
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CCur is internationally aware, which means that the return value is based on the locale settings on the machine. Numbers will be formatted with the appropriate decimal separator and the fourth digit to the right of the separator is rounded up if the fifth digit is 5 or higher.
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Example |
Dim dblValue, curValue dblValue = 724.555789 curValue = CCur(dblValue)
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See Also |
CBool, CByte, CDbl, CInt, CLng, CSng and CStr |
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CDate |
See under Date & Time functions |
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CDbl |
Returns an expression converted to Variant subtype Double (5).
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Syntax
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CDbl(expression)
expression is any valid expression.
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Note
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CDbl is internationally aware, which means that the return value is based on the locale settings on the machine. Numbers will be formatted with the appropriate decimal separator. A runtime error occurs if expression lies outside the range (-1.79769313486232E308 to -4.94065645841247E-324 for negative values, and 4.94065645841247E-324 to 1.79769313486232E308 for positive values) applicable to a Double.
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Example |
Dim dblValue dblValue = CDbl("5,579.56")
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See Also |
CBool, CByte, CCur, CInt, CLng, CSng and CStr |
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Chr |
Returns the ANSI character corresponding to charactercode.
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Syntax
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Chr(charactercode) |
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Note
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Supplying a charactercode from 0 to 31 will return a standard non-printable ASCII character.
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Example |
Dim strChar strChar = Chr(89)
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See Also |
Asc, AscB, AscW, ChrB and ChrW |
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ChrB |
Returns the ANSI character corresponding to charactercode.
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Syntax
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ChrB(charactercode) charactercode is a numeric value that indicates the character you want.
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Note
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Supplying a charactercode from 0 to 31 will return a standard non-printable ASCII character. This function is used instead of the Chr (returns a two-byte character) function when you only want the first byte of the character returned.
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Example |
Dim strChar strChar = ChrB(89)
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See Also |
Asc, AscB, AscW, Chr and ChrW |
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ChrW |
Returns the Unicode character corresponding to charactercode.
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Syntax
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ChrW(charactercode)
charactercode is a numeric value that indicates the character you want.
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Note
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Supplying a charactercode from 0 to 31 will
return a standard non-printable ASCII character. This function is used
instead of the Chr function when you
want to return a double byte character. For use on 32-bit Unicode enabled
platforms only, to avoid conversion
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Example |
Dim strChar strChar = ChrW(89)
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See Also |
Asc, AscB, AscW, Chr and ChrB |
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CInt |
Returns an expression converted to Variant subtype Integer (2).
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Syntax
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CInt(expression) expression is any valid expression.
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Note
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CInt is internationally aware, which means that the return value is based on the locale settings on the machine. Please note that decimal values are rounded, before the fractional part is discarded. A runtime error occurs if expression lies outside the range (-32,768 to 32,767) applicable to an Integer.
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Example |
Dim intValue intValue = CInt("5,579.56")
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See Also |
CBool, CByte, CCur, CDbl, CLng, CSng, CStr and the Math Functions Fix and Int |
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CLng |
Returns an expression converted to Variant subtype Long (3).
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Syntax
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CLng(expression) expression is any valid expression.
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Note
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CLng is internationally aware, which means that the return value is based on the locale settings on the machine. Please note that decimal values are rounded, before the fractional part is discarded. A runtime error occurs if expression lies outside the range (-2,147,483,648 to 2,147,483,647) applicable to a Long.
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Example |
Dim lngValue lngValue = CLng("5,579.56")
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See Also |
CBool, CByte, CCur, CDbl, CInt, CSng, CStr, and the Math Functions Fix and Int |
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CSng |
Returns an expression converted to Variant subtype Single (4).
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Syntax
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CSng(expression) expression is any valid expression.
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Note
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CSng is
internationally aware, which means that the return value is based on the
locale settings on the machine. A runtime error occurs
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Example |
Dim sngValue sngValue = CSng("5,579.56")
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See Also |
CBool, CByte, CCur,
CDbl, CInt,
CLng, CStr
and the Math Functions |
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CStr |
Returns an expression converted to Variant subtype String (8).
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Syntax
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CStr(expression) expression is any valid expression.
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Note
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CStr is internationally aware, which means that the return value is based on the locale settings on the machine. A runtime error occurs if expression is Null. Numeric and Err values are returned as numbers, Boolean values as true or false, and Date values as a short date.
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Example |
Dim strValue strValue = CStr("5,579.56")
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See Also |
CBool, CByte, CCur, CDbl, CInt, CLng, CSng and the Math Functions Fix and Int |
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Fix |
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Hex |
Returns the hexadecimal representation (up to 8 characters) of a number as a Variant subtype String (8).
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Syntax
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Hex(number) number is any valid expression.
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Note
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number is rounded to nearest even number before it is evaluated. Null will be returned if number is Null.
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Example |
Dim strValue strValue = Hex(5579.56)
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See Also |
Oct |
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Int |
See under Math functions |
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Oct |
Returns the octal representation (up to 11 characters)
of a number
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Syntax
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Oct(number) expression is any valid expression.
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Note
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number is rounded to nearest whole number before it is evaluated. Null will be returned if number is Null.
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Example |
Dim strValue strValue = Oct(5579.56)
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See Also |
Hex |
| << D.7.0- String constants | AppendixD | D.9.0- Unsupported conversion functions >> |
