Accessor methods for the hash class.

R style accesors for the hash-class.

Details

These are the hash accessor methods. They closely follow an R style.

$ is a look-up operator for a single key. The native $ method is used. The key is taken as a string literal and is not interpreted.

[[ is the look-up, extraction operator. It returns the values of a single key.

[ is a subseting operator. It returns a (sub) hash with the specified keys. All other keys are removed.

Value

$ and [[ return the value for the supplied argument. If a key does not match an existing key, then NULL is returned with a warning.

[ returns a hash slice, a sub hash with only the defined keys.

Author

Christopher Brown

See also

hash, values, .set, as.list

Examples

  h <- hash()
  h <- hash( letters, 1:26 )

  h$a       
#> [1] 1
  h$a <- "2"   
  h$z <- NULL          # Removes 'z' from 

  h[['a']] 
#> [1] "2"
  h[['a']] <- 23

  h[ letters[1:4] ]    # hash with a,b,c,d
#> <hash> containing 4 key-value pair(s).
#>   a : 23
#>   b : 2
#>   c : 3
#>   d : 4
  h[ letters[1:4] ] <- 4:1