Is this the expected behavior

Question

My apologies if this is kind of vague question as I am new to R. While experimenting with R I found one weird behavior. When I create a function like:

myfunction <- function(a,b){
    print(a,b)
}

and call it like:

myfunction(b = 10, a = 20)

it returns with result 20, but if I simply call it without function via assigning it directly to variables like:

a <- 20
b <- 10
print(a, b)

I get an error:

Error in print.default(a, b) : invalid 'digits' argument

Furthermore I have read that printing multiple variables in the same line can be accomplished via:

sprintf("%i %i",a, b)

So here is it a bug that it is appearing in function call with result as the first argument?

Answer 1

It might be revealing some underlying differences in how parameters are being handled in different scenarios but I don't think it's a bug.

If your intention is to print both values, consider changing:

print(a,b)

To something like:

print(paste(a,b))

From ?print.default:

# S3 method for default
print(x, digits = NULL, quote = TRUE,
  na.print = NULL, print.gap = NULL, right = FALSE,
  max = NULL, useSource = TRUE, …)

x       the object to be printed.

digits  a non-null value for digits specifies the minimum number of 
        significant digits to be printed in values. The default, NULL, uses 
        getOption("digits"). (For the interpretation for complex numbers see 
        signif.) Non-integer values will be rounded down, and only values 
        greater than or equal to 1 and no greater than 22 are accepted.
...

So R is expecting everything that you actually want to print to be contained in the first variable (x).

Based on your results and some of the comments, apparently in some cases the second variable is being accepted as a valid digits parameter value and in other cases it is not.

While this is a little odd, the more important point is that print(a,b) is not a syntactically correct way to print multiple values.