Re: string function: definition of a function

[Ethan M. <merritt@u.washington.edu>]

On Saturday 31 January 2009 02:15:49 Petr Mikulik wrote:
> > I propose the patch below, which adds a function that returns the
> > string that defines a specified user defined function.
> 
> I see it gives the following:
>         GPFUN_f = "f(x,y)=x+y+20"
>         GPFUN_g = "g(x,y)=x*y"
> 
> I wonder how I can get the definition part only, i.e. "x+y+20" or "x*y".
> Maybe you could add another variable
> 	GPFUN__f = "x+y+20"
> ?
> 
> I though there are some "string" functions that could allow this, but it 
> seems we don't have "string index" or "string split" functions.

We do. It is called strstrt(haystack,needle):

gnuplot> show var GPFUN
        GPFUN_f = "f(a,b) = a**2 + sqrt(b*a)"

gnuplot> print strstrt(GPFUN_f,"=")
	8
gnuplot> print GPFUN_f[ strstrt(GPFUN_f,"=") : * ]
	= a**2 + sqrt(b*a)
gnuplot> print GPFUN_f[ strstrt(GPFUN_f,"=")+1 : * ]
	 a**2 + sqrt(b*a)
gnuplot> body = GPFUN_f[strstrt(GPFUN_f,"=")+1:*]
gnuplot> print body
	 a**2 + sqrt(b*a)






> 
> Maybe it would be also useful to have
> 	strindex("hello world", "llo")  => 3
> 	strsplit("hello=world", "=", 0) => "hello"
> 	strsplit("hello=world", "=", 1) => "="
> 	strsplit("hello=world", "=", 2) => "world"
> 
> ---
> PM
> 
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-- 
Ethan A Merritt
Biomolecular Structure Center
University of Washington, Seattle 98195-7742