R help - Dec 2009 - How to define new operators

Dear R community

I try to create a new operator to build a special sum of two CashFlows. (my  
S4 Class)

I tried the following but this is actually not what I want.

setGeneric("++",function(e1,e2)standardGeneric("++"))

setMethod("+",signature=list("CashFlow","CashFlow"),function(e1,e2){
print("+")
})
setMethod("++",signature=list("CashFlow","CashFlow"),function(e1,e2){
print("++")
})

The problem here is that this work but it treats "++" as a general  
function.. the call is "++"(e1,e2).
I'm looking for somthing like e3 <- e1 ++ e2

Thanks a lot for your help.
Best regards,
Roger

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On 18/12/2009 10:22 AM, bergarog at gmail.com wrote:
> Dear R community
>
> I try to create a new operator to build a special sum of two CashFlows. (my
> S4 Class)
>
> I tried the following but this is actually not what I want.
>
> setGeneric("++",function(e1,e2)standardGeneric("++"))
>
>
setMethod("+",signature=list("CashFlow","CashFlow"),function(e1,e2){
> print("+")
> })
>
setMethod("++",signature=list("CashFlow","CashFlow"),function(e1,e2){
> print("++")
> })
>
> The problem here is that this work but it treats "++" as a
general
> function.. the call is "++"(e1,e2).
> I'm looking for somthing like e3 <- e1 ++ e2
The R parser limits the operators it recognizes to the predefined ones, 
plus user-defined ones of the form %op% (where op could be ++ if you 
liked).  You can't define ++ as an operator because the parser will see 
it as two plus signs, not as a single infix operator.

Duncan Murdoch