* * * * *
                                        
                       Ideas in parsing the command line
                                        
> For any non-trivial script, even for personal consumption, it's necessary
> to supply usage text. The novelty of Lapp is that it starts from that point
> and defines a loose format for usage strings which can specify the names
> and types of the parameters.
> 
> An example will make this clearer:
> 
> -----[ Lua ]-----
> 	-- scale.lua
> 	  require 'lapp'
> 	  local args = lapp [[
> 	  Does some calculations
> 	    -o,--offset (default 0.0)  Offset to add to scaled number
> 	    -s,--scale  (number)  Scaling factor
> 	     <number> (number )  Number to be scaled
> 	  ]]
> 
> 	  print(args.offset + args.scale * args.number)
> -----[ END OF LINE ]-----
> 

“lua-users wiki: Lapp Framework [1]”

The thought of parsing the usage text for parsing the command line never
occured to me, and I think it's brilliant.

Now, when I want to modify the command line of a program I wrote (and this is
mostly in C, by the way), there are four locations I have to edit:

  1. An enumeration specifying the “short” form of the command line option
  2. A structure describing both the short and the long forms of a command
     line option
  3. A switch statement that processes the command line options from
     getopt_long()
  4. The text printed out describing the command line options

This method though, there's only one area I would have to edit.

Now granted, this is only for Lua, but I can't see why something similar for
other languages can't be done.

[1] http://lua-users.org/wiki/LappFramework

Email Sean Conner at sean@conman.org

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