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MathGroup Archive 2007

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Re: search for an operator in an expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg78204] Re: search for an operator in an expression
  • From: rob <josh2499 at hotmail.com>
  • Date: Tue, 26 Jun 2007 04:05:38 -0400 (EDT)
  • References: <f5iuqu$a99$1@smc.vnet.net> <f5o8jr$5jo$1@smc.vnet.net>

Sir, I tried your suggestion as follows:

expr = 2 + a*Exp[-b x] + Sin[c + b] + d

Count[expr, HoldPattern[Plus[__]], Infinity]

which gives a result of "1". I count 4 "+" in expr. Please, 
what am I doing wrong? Thanks.

dh wrote:

> Hi Daniel,
> 
> you may use "Count". Take care to search on all "levels" and prevent 
> 
> evaluation of the operator. Asssuming your expression is in: expr, e.g.:
> 
> Count[expr, HoldPattern[ Plus[__] ], Infinity]
> 
> hope this helps, Daniel
> 
> 
> 
> 
> 
> Daniel wrote:
> 
> 
>>Is there a way to search for an operator in a symbolic expression? My wish is to show that there is only "+" in a very large expression. Rather than showing an expression on multiple pages I would like to perform a search that shows there is only "+" between the terms. Converting to a string does not seem to work since the expression is written on multiple lines(fractions, exponents etc..)
> 
> 
> 
>>Thanks
> 
> 
> 
> 
> 


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