Names of bigq vectors (R package gmp)

Question

The names function for bigq vectors of the gmp R package does not work as one could expect:

> library(gmp)
> x <- as.bigq(c(0.5,0.5))
> names(x) <- c("a", "b")
> names(x)
 [1] "a" "b" NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA  NA 

Thus I define a names function for the bigq class as follows, and it works fine:

> names.bigq <- function(x) attr(x, "names")[1:length(x)]
> names(x)
[1] "a" "b"

Even names(x) <- and setNames work fine with the names.bigq function. But the access to an element of a vector by its name does not work:

> x["a"]
bigq(0)

Is there a way to make it work ? If x["a"] were the same as x[which(names(x)=="a")] then it would be fine:

> x[which(names(x)=="a")]
Big Rational ('bigq') :
[1] 1/2

Note: A possible workaround consists in converting and back-converting x in character mode.

Answer 1

The function extracting an element in a bigq vector or matrix by its index is the internal `[.bigq` function:

> gmp:::`[.bigq`
function (x, i = NULL, j = NULL, drop = TRUE) 
{
    .Call(matrix_get_at_q, x, i, j)
}
<environment: namespace:gmp>

Then overwrite it by this one:

`[.bigq` <- function (x, i = NULL, j = NULL, drop = TRUE) 
{
  if(is.character(i)){ i <- which(names(x)==i) }
  .Call(gmp:::matrix_get_at_q, x, i, j)
}

And it works:

> x <- as.bigq(c(2,5))
> names(x) <- c("a", "b")
> x[1]
Big Rational ('bigq') :
[1] 2
> x["a"]
Big Rational ('bigq') :
[1] 2

Better:

`[.bigq` <- function (x, i = NULL, j = NULL, drop = TRUE) 
{
  if(is.character(i)){ i <- sapply(i, function(k) which(names(x)==k), USE.NAMES=FALSE) }
  .Call(gmp:::matrix_get_at_q, x, i, j)
}

to get:

> x[c("a","b")]
Big Rational ('bigq') object of length 2:
[1] 1 2
> x[c("b","a")]
Big Rational ('bigq') object of length 2:
[1] 2 1