Adhoc named parameters

[figurcoe]

Hi,

please find attached a suggestion for a syntax extension. This features adhoc named parameters (for a lack of a better name).

In my usecase it would be very desireable to be able to use the clean syntax of named parameters without the need to write a package with potentially thousands of autogenerated procedures with lots of named parameters, each given default values. I have the possibility to check in the body whether the adhoc named parameter(s) are sensible in the given context and can provide default values for the not given, but in the given context required additional parameters. This extension wouldn't break the existing functionality but would increase the flexibility.

Thanks for considering.

[figurcoe]

I changed the way those "adhoc named parameters" are made available within the procedure. Now they are collected within the dict kwargs. Therefore, a better name would be keyword arguments.

package require np 1.1.1

np::proc test { {a 1} {b 2} {c 3} -- {ARGS ""}} {
    puts "Variables known in proc:"
    puts "+-NAMED------------------------------------------------------------"
    puts "|"
    puts "|a: $a"
    puts "|b: $b"
    puts "|c: $c"
    puts "|"
    puts "+-POSITIONAL-------------------------------------------------------"
    puts "|"
    puts "|ARGS: $ARGS"
    puts "|"
    puts "+-KWARGS-----------------------------------------------------------"
    puts "|"
    dict for {key value} $kwargs {
        puts "|$key: $value"
    }
    puts "|"
    puts "+------------------------------------------------------------------"
}

test -a 11  =d 44 -b -22 -- "filling up ARGS"

will give

Variables known in proc:
+-NAMED------------------------------------------------------------
|
|a: 11
|b: -22
|c: 3
|
+-POSITIONAL-------------------------------------------------------
|
|ARGS: filling up ARGS
|
+-KWARGS-----------------------------------------------------------
|
|d: 44
|
+------------------------------------------------------------------

as output.

[figurcoe]

An additional comment: Of course the syntax with '=' identifying keyword parameters could be changed to a more open approach.

The '=' could be ditched and whenever a named parameter (starting with '-') is encountered it will be handeled as before and in case it is not defined in the proc-head, it will be made available as keyword-parameter in the dict. This would result in a more consistenly looking syntax close to an approach as many might know from e.g. python. But this would give up the clear distinction between named parameters that are expected to be defined and those keyword parameters.

If you were to get real crazy and push the door wide open, one could think about:

• "-parameter" --> named parameter as right now
• "-parameter" --> keyword parameter, if not a valid named parameter defined in proc-head
• "=parameter" --> adhoc named parameter directly available in proc's scope (as named parameters are)

To be honest I do not really see why one should want this, but it would be a flexible option, handing power to the user.

I personally would need an option to introduce named parameters in a readable way, without having to predefine them in the proc-head. This would be achieved by this pull request. If those keyword parameters are indicated via '-' or '=' is probably a matter of personal preference, as I can see points in favour of both implementations. I would slightly tend towards ditching the '=' in favour of using '-' for both. But that's obviously your call.

Thanks for considering.