Re: Parsing functions - do I need a keyword like 'def' to indicate a function?

Alex Colvin <alexc@TheWorld.com>
17 Oct 2004 16:06:41 -0400

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From: Alex Colvin <alexc@TheWorld.com>
Newsgroups: comp.compilers
Date: 17 Oct 2004 16:06:41 -0400
Organization: The World : www.TheWorld.com : Since 1989
References: 04-10-092
Keywords: syntax, design
Posted-Date: 17 Oct 2004 16:06:41 EDT

>I'm trying to create a simple scripting language using lex and yacc. I've
>noticed that the grammars for most scripting languages have some kind of
>keyword in front of function declarations. For example:


>for example in python you use: def setColor (r, g, b):


>I was wondering why that is. I suspect the point is to avoid of ambiguity


Most scripting languages, unlike most other languages, accept
statements outside of procedures, to be executed immediately.


This leads to an ambiguity for setColor(a,b,c), which is resolved in favor
of the statement. A definition requires the extra "def" token.
I suppose they could have required an extra token "call" in front of the
statement.


>func_name '(' param_list ')' IS_TOKEN
> func_body
>END_TOKEN


>Does anyone have any suggestions as to whether or not I should have/need a
>keyword in front?


Can your parser can handle it after the function? It means you don't know
whether you're looking at a call or a definition until the IS_TOKEN.


--
mac the naïf

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