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:

>

```

-- 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)

```

“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

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