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Kovid Goyal 2020-10-16 07:34:00 +05:30
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manual/template_lang.rst
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@ -361,10 +361,10 @@ Both General and Template Program Modes support ``if`` expressions with the foll
``if`` <<expression>> ``then``
<<expression_list>>
[``elif`` <<expression>> then <<expression_list>>]*
[``elif`` <<expression>> then <<expression_list>>]*
[ ``else`` <<expression_list>> ]
``fi``
The elif and else parts are optional. The words ``if``, ``then``, ``elif``, ``else``, and ``fi`` are reserved; you cannot use them as identifier names. You can put newlines and white space wherever they make sense. <<expression>> is one template language expression; semicolons are not allowed. <<expression_list>> is a semicolon-separated sequence of template language expressions, including nested ifs. Examples:
* ``program: if field('series') then 'yes' else 'no' fi``
@ -408,7 +408,7 @@ Examples of calling a template, assuming the stored template is named ``foo``:
* ``foo(if field('series') then field('series_index') else 0 fi)`` -- if the book has a ``series`` then pass the ``series_index``, otherwise pass the value ``0``.
In the stored template you retrieve the arguments passed in the call using the ``arguments`` function. It both declares and
initializes local variables, effectively parameters. The variables are positional; they get the value of the value given in
initializes local variables, effectively parameters. The variables are positional; they get the value of the value given in
the call in the same position.
If the corresponding parameter is not provided in the call then ``arguments`` assigns that variable the provided default value. If there is no default value then the variable is set to the empty string. For example, the following ``arguments`` function declares 2 variables, ``key``, ``alternate``::
@ -427,7 +427,7 @@ shortcut will help switching more rapidly between the tester and editing the sto
Notes on the difference between modes
-----------------------------------------
The three template program modes, Single Function Mode (SFM), Template Program Mode (TPM), and
The three template program modes, Single Function Mode (SFM), Template Program Mode (TPM), and
General Program Mode (GPM), work differently. SFM is intended to be 'simple' so it hides a lot
of programming language bits. For example, the value of the column is always passed as an 'invisible' first argument
to a function included in the template. SFM also doesn't support the difference between variables
@ -462,7 +462,7 @@ TPM and GPM do support nested functions. The above template in TPM would be::
In TPM it would be::
program: uppercase(substr(field('series'), 0,5))
User-defined Python template functions
------------------------------------------
@ -514,7 +514,7 @@ You might find the following tips useful.
* Use the Template Tester to test templates. Add the tester to the context menu for books in the library and/or give it a keyboard shortcut.
* Templates can use other templates by referencing composite columns built with the desired template. Alternatively, you could
use Stored Templates.
use Stored Templates.
* In a plugboard, you can set a field to empty (or whatever is equivalent to empty) by using the special template ``{}``. This template will always evaluate to an empty string.
* The technique described above to show numbers even if they have a zero value works with the standard field series_index.