Re: Definition of Semantic: was What Lua can do that other programming languages can't do?

[Sean Conner <sean@...>]

It was thus said that the Great Javier Guerra Giraldez once stated:
> On Wed, Mar 27, 2013 at 1:45 AM, Ross Bencina
> <rossb-lists@audiomulch.com> wrote:
> >
> >>> Attempts to go
> >>> beyond that fail in the same way silly ideas like the "semantic
> >>> web" nonsense of a few years back.
> > 
> > I'm not sure where you're going here, but I think there is a need to
> > differentiate between the general field of semantics in human knowledge and
> > what is meant by "semantic" in programming languages theory (ie "semantic
> > analysis" etc) -- which just means how to the language symbols map to
> > machine operations or to the lambda calculus. This has nothing to do with
> > "human meaning"
> 
> syntax and semantics come from linguistics.  in human languages,
> there's syntax (this is a verb, this a noun, this a noun predicate,
> etc) and semantics ("running" and "jumping" are both physical
> activities, "to care" is an intransitive verb, "man", "woman" and
> "child" are all humans, etc)

  A good example is this sentence:

	Fruit flies like a banana, but time flies like an arrow.

  Syntactically, there are four possible parsings for this sentence:

	(1) Adj  Noun Verb Art Noun , Conj Adj  Noun Verb Art Noun
	(2) Adj  Noun Verb Art Noun , Conj Noun Verb Prep Art Noun
	(3) Noun Verb Prep Art Noun , Conj Adj  Noun Verb Art Noun
	(4) Noun Verb Prep Art Noun , Conj Noun Verb Prep Art Noun

  Semantically, only (2) is correct, unless you know of fruit that does,
indeed, fly, or a group of insects known as "time flies."  

  In Lua, you can have:

	P(5) / function(c) return tonumber(c) end

  Is syntactically correct, assuming P is defined and can be used in a
function call context.  Semantically, it can mean different things depending
on how P and c are defined.  Here, it means one thing:

	function P(x) return 2 * x + 1 end
	c = "0.5"

but it has a different meaning this way:

	P = require "lpeg".P

  -spc (Darn!  My time flies got out again!)