spatstat.utils (version 3.1-2)

orifnull: Specify a Default Value

Description

Specify a value together with a default to be used when the first value is null.

Usage

a %orifnull% b

Value

The result is a if a is not NULL, and otherwise the result is b.

Arguments

a

Any kind of object or expression to be evaluated.

b

Default value to be used when a is NULL. Any kind of object or expression to be evaluated.

Author

Adrian Baddeley , Rolf Turner and Ege Rubak

Details

The operator %orifnull% is designed to improve the readability of code.

a %orifnull% b is equivalent to if(is.null(a)) a else b.

That is, a %orifnull% b is equal to a provided a is not null, and otherwise the result is equal to b.

Expressions are evaluated only when necessary. If a is a language expression, it is first evaluated. Then if is.null(a) is FALSE, the result is a. Otherwise, b is evaluated, and the result is b. Note that b is not evaluated unless a is NULL.

The operator %orifnull% has higher precedence than the arithmetic operators +, -, *, / but lower precedence than ^.

The operator is associative, and can be used repeatedly in an expression, so that a default value may have its own default. See the Examples.

Examples

   x <- 7
   y <- 42
   z <- w <- NULL
   x %orifnull% y
   z %orifnull% y
   z %orifnull% x %orifnull% y
   z %orifnull% w %orifnull% y