Symbolic expressions

Both Tarma Installer and Windows Installer allow the use of symbolic expressions in many places. There are two styles of symbolic expressions:

• Tarma Installer style, using < and > to enclose the expression, for example <ProgramFilesFolder>.
• Windows Installer style, using [ and ] to enclose the expression, for example [ProgramFilesFolder].

You can use the Tarma Installer style everywhere in Tarma ExpertInstall. If you build a Windows Installer package, Tarma ExpertInstall will convert any Tarma-style expressions to the Windows Installer syntax. Tarma ExpertInstall also performs extensive syntax and cross-reference checking on symbolic expressions that use the Tarma-style syntax.

You can use the Windows Installer-style syntax in items that are only used by Windows Installer packages, for example the Windows Installer action sequences and dialog boxes. However, Tarma ExpertInstall will NOT convert Windows Installer-style expressions to Tarma-style syntax if you build a Tarma Installer package, and it will NOT perform syntax or cross-reference checking on Windows Installer-style expressions.

For these reasons, we recommend that you use Tarma-style syntax throughout the project.

Note 1: When you import an MSI database or merge module, Tarma ExpertInstall converts all Windows Installer-style expressions to Tarma-style syntax.

Note 2: In build actions you can only use Tarma Installer style references. Windows Installer style references are not recognized in that context.

Windows Installer has only limited support for symbolic expressions. For example, you cannot use recursive expressions, no registry or INI file lookup, no runtime functions, no alternate values, and no platform-specific values. If you use any of these, Tarma ExpertInstall will issue a diagnostic message and will try to convert the expression at build time. However, this may not always have the desired effect.

Usage

Symbolic expressions can be used for many purposes:

• Folder paths: for example, <ProgramFilesFolder> returns the folder path of the "Program Files" folder on the target system, localized as appropriate; <$comp_name> returns the folder path that is associated with component comp_name.
• File paths: for example, <#file_alias> returns the installation path of the file with alias file_alias.
• General text: for example, <ProductName> returns the name of the product that is being installed.
• General and system variables: for example, <TsuQuiet> returns the user interface level of the installer; <VersionNT> returns the Windows version if the installer runs on a Windows NT-based system.
• Auxiliary variables: for example, <UIRegistrationPage> is used to control support for the customer registration functionality.
• Runtime information: for example, <%ComSpec> returns the path to the command processor on the target system; <@<HKCU>\Software\<Publisher>\<ProductName>\User> returns the value of the (hypothetical) User registry value under the product's registry key.
• Runtime functions: for example, <$sfn(<#file_alias>)> returns the short file name (8.3) version of the path to the file with alias file_alias; <$fverp(<#file_alias>)> returns the product version of the same file.

Furthermore, symbolic expressions and variables are used in conditional expressions.

Syntax

The symbolic expression syntax is defined as follows.

• Items in italics are non-terminals.
• Items in bold are keywords or literal symbols.
• Underlined items are extensions for Tarma Installer (only).
• The pipe character '|' indicates a choice.
• ...something... items are informal definitions of terms.
• Names are mostly case-sensitive for Windows Installer, but case-insensitive for Tarma Installer. We recommend that you treat all names as if they were case-sensitive and do not create names that differ only in case.
• Recursive symbolic expressions are allowed up to a depth of 32 in Tarma Installer. Windows Installer does not support recursive symbolic expressions.

symexpr	::= < expr >
expr	::= varname | #filealias | $compname | %envvar | @regpath |
	    $func(params) | #filepath?section?key | !expr | expr=expr
varname	::= ...name of a product variable (may use symbolic expressions)...
filealias	::= ...alias of installation file (may use symbolic expressions)...
compname	::= ...component name (may use symbolic expressions)...
envvar	::= ...environment variable name (may use symbolic expressions)...
regpath	::= ...path to registry value (may use symbolic expressions)...
func	::= ...name of runtime function...
filepath	::= ...file path (may use symbolic expressions)...
section	::= ...INI file section name (may use symbolic expressions)...
key	::= ...INI file key name (may use symbolic expressions)...

Non-symbolic expressions

To prevent Tarma ExpertInstall from interpreting some text as a symbolic expression, enclose the text in backticks: `...some text...`. You can do this for the entire text, or only for the portions that must not be interpreted. For example:

`<ProgramFilesFolder>`

Resolves to the literal text <ProgramFilesFolder>

`<ProgramFilesFolder>`=<ProgramFilesFolder>

Resolves to <ProgramFilesFolder>=...value of ProgramFilesFolder variable...

`12345<###-%%%%%%%>@@@@@`

Prevents interpretation of the <...> portion in the value (from the PIDTemplate variable).

Expression prefixes

The following prefixes can be used in expr expressions.