Extract function

Extract or replace parts of a hyper2 object

## S3 method for class 'hyper2'
x[...]
## S3 replacement method for class 'hyper2'
x[index, ...] <- value
assign_lowlevel(x,index,value)
overwrite_lowlevel(x,value)

Arguments

• x: An object of class hyper2
• ...: Further arguments, currently ignored
• index: A list with integer vector elements corresponding to the brackets whose power is to be replaced
• value: Numeric vector of powers

Details

These methods should work as expected, although the off-by-one issue might be a gotcha.

For the extract method, H[L], a hyper2 object is returned. The replace method, H[L] <- value, the index specifies the brackets whose powers are to be overwritten; standard disordR protocol is used.

If the index argument is missing, viz H1[] <- H2, this is a special case. Argument H1 must be a hyper2 object, and the idiom effectively executes H1[brackets(H2)] <- powers(H2), but more efficiently (note that this operation is well-defined even though the order of the brackets is arbitrary). This special case is included in the package because it has a very natural C++

expression [function overwrite() in the src/ directory] that was too neat to omit.

Altering (incrementing or decrementing) the power of a single bracket is possible using idiom like H[x] <- H[x] + 1; this is documented at Ops.hyper2, specifically hyper2_sum_numeric() and a discussion is given at increment.Rd.

Functions assign_lowlevel() and overwrite_lowlevel() are low-level helper functions and not really intended for the end-user.

Returns

The extractor method returns a hyper2 object, restricted to the elements specified

Author(s)

Robin K. S. Hankin

Note

Use powers() and brackets() to extract a numeric vector of powers or a list of integer vectors respectively.

Replacement idiom H[x] <- val cannot use non-trivial recycling. This is because the elements of H are stored in an arbitrary order, but the elements of val are stored in a particular order. Also see function hyper2_sum_numeric().

See Also

hyper2,Ops.hyper2

Examples

data(chess)

chess["Topalov"]
chess[c("Topalov","Anand")]
chess[c("Anand","Topalov")]

# Topalov plays Anand and wins:

chess["Topalov"] <- chess["Topalov"]+1 
chess[c("Topalov","Anand")] <- chess[c("Topalov","Anand")]-1

# Topalov plays *Kasparov* and wins:
chess["Topalov"] <- chess["Topalov"] + 1
chess[c("Topalov","Kasparov")] <- chess[c("Topalov","Kasparov")] -1

# magrittr idiom:
# chess["Topalov"] %<>% inc
# chess[c("Topalov","Kasparov")] %<>% dec  

# overwriting idiom:
H <- hyper2(list("Topalov","X"),6)
chess[] <- H

H <- icons