\procedure vs \define

1

Until recently, I was not aware of \procedure. I don’t use them yet.

I can’t really see in the doc what it does better than \define. Except using the \parameters pragma. But the docs don’t really show why it would be such a great feature. Would the combination of the two works better (than \define) if I use functions (defined by \function) in my filter? And again, how’s that?

Also’ in the " Macro Definition Syntax" there is no mention of \procedure. What are we creating with \procedure?

2

You might want to read #4673, which contains a lot of information about this and links to more.

For that matter, I should re-read it, as I still haven’t internalized them. :grinning_face_with_smiling_eyes:

3

@jypre https://tiddlywiki.com/#Variable%20Usage

4

@CodaCoder In variable usage, I can read

<$set name="sp2" value="""
\parameters(a1)
<$parameters a1><<a1>></$parameters>
""">

I suppose it is meant to say that you can do

<$set name="sp2" value="""
\parameters(a1)
<<a1>>
""">

otherwise I don’t see the use of \parameters(a1). This is indeed the case (just tested it). I think the doc has wanted to be a bit shorter that it should have been.

5

Thank you @Scott_Sauyet for the link.

Now I krow that \procedure is the new macro mechanism and I ought not to use \define anymore. A good point for this being there is no more (slow) text substitution.

So we definitely must update the doc about macro, mustn’t we?

6

I read in this help page that with \defined macro called along the usual way, that “all wikitext and variable substitution and textual substitution takes place”.

But this is not illustrated. I may be a bit dumb’ but what is the difference with “All wikitext and variable substitution takes place”? There in tiddler called “textual substitution” (or including that in its title) to enlight me. I //suspect// this is the bit about using $myFirstArg$ for instance. Is that so?

7

I don’t know. I had exactly the same question when I read it – I wondered why “textual substitution” was added. I figured I’d glossed over something and never did go back to see what I’d missed.

8

In “Variable usage” all the usage is within a simple wiki context. Ther is not a word about filter context.

My tests indicate this is a whole different story. A lot of things are different (read as producing blank only).

9

In fact one may argue its poorer as the variable substitutions are now ONLY as variables. However with the parameters widget and “functions” now available (that allows many forms of substitution), I think we have “won back” the functionality.

  • The advantage of parameters as “only” variables is we can now focus on parameters as having a consistent representation.
  • The way the new functions work you can replace 90% even 100% of the reasons for using the \define substitutions by moving them into filters (\functions) which has it’s own values. See also substitution operator.

(As I understand it) keep in mind this is part of gradual change and a move to procedures is part of a larger picture by the core team, the value will only be fully realised in time

Despite the above this is also true

  • Define and substitution features are only depricated and I cant see them ever going completely (speculation).
    • But is wise to migrate away from them.
  • You can nest \defines inside custom widgets and procedures, and use them in that scope.
  • You can call defines and procedures, with <$transclude $variable= and procedures with <$macrocall $name= when you do not need to use a feature of the new $transclude $variable.
  • using functions, and the new backtick attribute values allows you to avoid definition of a macro (\define) by providing an “evaluated value” as an attribute value right where it is needed.