Re: Give parts of commands/definitions to a called command (to parse arguments)

[Valery Ushakov]

On Fri, Apr 22, 2016 at 01:37:28 +0200, Oliver Bandel wrote:

> >On Wed, Apr 20, 2016 at 19:33:38 +0200, Oliver Bandel wrote:
> >
> >>def vvec
> >>  right body
> >>  { pmatrix strut { Yes }  body }
> >>
> >>The body is nor parsed again, so it is not seen as command, when using
> >>
> >>    vvec { row col a row col b row col c }
> >>
> >>inside @Eq.
> >[...]
> >>Or are there other ways to achieve my goal?
> >
> >Just use a macro.  "pmatrix" itself is a macro that supplies some
> >additional paramters to "matrix".
> >
> >    import @Math macro vvec { pmatrix strut { Yes } }
> [...]
> 
> Thanks, that works :-)
> 
> What I had first in mind was going far beyond that...
> ,,,because I wanted to have vvec working in a way, so that I only
> need to give the elements of the vector, and don't need to
> type in the "row" and "col" keywords.
> This would need to have a way to parse an argument list.
>
> It would be nice to then use only:
> vvec( 2, 3, 4, 55, 6 )
> 
> and the values wil be set each on a seperate row and col.

If I got this right:

  extend @Math matrix
  def ","
    associativity left
    left  x
    right y
  {
      row col x row col y
  }

and then

  vvec { a, b, c } 


> >>Is there a way to parse the body inside the vvec-command?
> >
> >Ugm, ... jein...  Using extend or import on a named paramter, like in my
> >previous example with "int".  But the problem is that the body will be
> >evaluated in the wrong environment.
> [...]
> 
> I'm not familiar with all the import/extend/... stuff.

Read the Expert's Guide.


> Also ... what is just "@" as argument name?

Just a convenient short name, not really different from "foo" or
"@InitialLanguage".  The at-sign doesn't have special meaning in Lout,
but since it's conventionally used as a name prefix, it makes a
natural single-letter name if you must have some special named
parameter.


-uwe