[R] ?for

[Ray Brownrigg]

Peter Dalgaard <p.dalgaard at biostat.ku.dk> writes:
> 
> Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:
> 
> > You have typed a syntactically incomplete statement: this is explained in 
> > ?help.
> > 
> > Hint: ?"for" and help("for") work.
> 
> [Original question added back in:
> On Sun, 16 Nov 2003, Angel wrote:
> 
> > I have always been intrigued by why ?for (or ?if,?while,etc) leave R
> > wanting for more:
> > > ?for
> > +
> > I know the help for these is in ?Control, but I sometimes make the
> > mistake of typing ?for instead. What is R expecting me to say to finish
> > the statement?
> ]
> Further hint: ? is an operator, syntactically similar to + and -. You
> can apply operators to the result of a for loop. Consider for example
> 
> x <- 1; - for (i in 1:10) x <- x * i
> 
> (? has special semantics, but that is not noticed at parse time).
> 
Unfortunately the original question still hasn't been answered
explicitly, not even in ?help.
Try:
> ?for
+ (i in 0) 0
or:
> ?if
+ (T) T
or:
> ?+
+ 0

So you have to provide the rest of a syntactically complete statement.

Just to see if you now understand exactly how ? works, what do you
think:
? paste("help")
will do?

Ray Brownrigg