Make a Webel help Rule for a required ‘$arg$’ argument + conventions

Gallery
Tutorial
[TECHNICAL SLIDE TRAIL] The Webel libraries for Wolfram Mathematica: With SysMLv1 models.
Section
SECTION: The Webel '$opt$' and '$arg$' help holder conventions for options and arguments in the Wolfram Language
Mathematica keywords
Rule
Association
Webel Mathematica keywords
help holder
'$arg$'
'def$arg$'
'rule$arg$'
'$info$arg$'
'$warn$arg$'
'$lab$arg'
makeArgRuleReq
help Rule
Keywords
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The Doc` function makeArgRuleReq creates a help Rule for a required argument with keys compatible for:
Webel: Mathematica: A help Rule 'rule$arg' for an '$arg$' (argument) accepts keys: '$k$help' (required), '$k$def' (required if $k$req = True not given), '$k$req' (True if $k$def not given), '$k$warn', '$k$tip', '$k$lab', '$k$type', '$k$mult' and '$k$pat'

Please note that at this stage we are only examining use of the Webel '$arg$' help holders conventions in lower-level packages, which rely on "manual" naming conventions; in later slides we'll see how Webel extensions of MTools for OO such as the MArg class can be used to encapsulate the help holders for the Webel arguments convention.

Up next
Make a Webel argument help Rule with a default by convention OR override
Notes
[NAMING, PATTERN, POLICY]{STRICT} Webel: Mathematica: A help Rule 'rule$arg' for an '$arg$' (argument) accepts keys: '$k$help' (required), '$k$def' (required if $k$req = True not given), '$k$req' (True if $k$def not given), '$k$warn', '$k$tip', '$k$lab', '$k$type', '$k$mult' and '$k$pat'
[NAMING, PATTERN, POLICY]{STRICT} Webel: Mathematica: CONVENTION: Argument help holders use a String variable with the prefix '$arg$', a related '$info$arg$' String, a 'def$arg$' default value expression and/or 'req$arg$', and optional '$warn$arg$', '$tip$arg$, '$lab$arg$', 'type$arg$'..
[NAMING, PATTERN, POLICY]{STRICT} Webel: Mathematica: CONVENTION: An '$opt$' (option) or '$arg$ (argument) help holder may be have an associated (typically short) '$lab$opt$' or '$lab$arg$' label help holder for use in GUIs and views.
[POLICY]{STRONG} About the Single Source of Truth (SSOT) and Don't Repeat Yourself (DRY) principles
[NAMING, OPTION, PATTERN, TIP]{OPTION} Mathematica: Webel: You CAN/MAY use $ in variable names and function names - just not as the first character before a Capital - and it's extremely useful. You won't get sent to Azkaban prison if do you use a $ character!
Snippets (quotes/extracts)
Visit also
The Webel SysML4Mathematica recipe for modelling Wolfram Language code in Systems Modeling Language (SysML) for Model-Based Systems Engineering
Visit also (backlinks)
Related slides (includes other tutorials)
The Webel '$opt$', 'rule$opt$', '$arg$', 'rule$arg$' and supporting '$k$' conventions for "help holders"
Webel ‘$arg$’, ‘def$arg$’, and ‘rule$arg$’ convention
Webel '$arg$' and '$opt$' support via the Doc` package
Related slides (backlinks, includes other tutorials)
Generate $doc$arg$ and $doc$opt$ Strings from Webel help Rules for use in ::usage
When to use explicit $arg$ help holders (in lower level utility packages)
Why not just generate all the '$arg$' and '$opt$' help holders (using ToExpression)?
Why not just use the Entity system for '$arg$' and '$opt$' help holders?