Using Tarma Workshop > Symbolic expressions

Symbolic expressions

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.
The pipe character '|' indicates a choice.
...something... items are informal definitions of terms.
Names are case-insensitive. We recommend that you do not create names that differ only in case.
Recursive symbolic expressions are allowed up to a depth of 32 in Tarma Installer.

symexpr	::= < expr >
expr	::= varname | #filealias | $compname | %envvar | @regpath |
	    $func(params) | #filepath?section?key | !expr | expr=expr
varname	::= ...name of a symbolic 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 Installer 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...

Expression prefixes

The following prefixes can be used in expr expressions.

Prefix	Operands	Result
(no prefix)	Variable name	Value of the symbolic variable, with all symbolic references resolved. See Alphabetical reference for a full list of predefined symbolic variables; you can add your own variables on the Symbolic Variables project page.
#	File alias	Installation path of the corresponding file.
#...?...?...	INI file path, section, key	Value from the corresponding INI file, section, and key, retrieved from the target system at installation time.
$...(...)	Function name, parameters	Result from the corresponding runtime function. The required parameters depend on the function. See Runtime functions for a full list.
%	Environment variable	Value of the corresponding environment variable, retrieved from the target system at installation time.
@	Registry value path	Value of the corresponding registry value, retrieved from the target system at installation time. Note: To retrieve the (default) value of a registry key, terminate the registry value path with a backslash ('\').
!	Symbolic expression	The value of the symbolic expression without double lookup. This allows, for example, expressions like <@<ShellFoldersCU>\My Pictures=!<PersonalFolder>\My Pictures> to behave as expected, instead of treating <...<PersonalFolder>...> as a lookup of the PersonalFolder variable, followed by an attempt to look up the non-existing variable whose name was retrieved from PersonalFolder.
=	Alternate expressions	If the left operand is not empty, the left operand; else the right operand. You may use a sequence of alternate expressions to try them all in succession: expr1=expr2=expr3=...