Inlinable Marker Function for Function Development

This inlinable function outputs a user modifiable message identifying its enclosing function using sys.call then returns its first argument, if any.

Usage

marker(rval = NULL, msg = "in Mimiland")

Arguments

rval

value to be returned; default NULL.

msg

ending of the output message. Since this argument follows rval, which normally would only ever be supplied inline, its name cannot be omitted unless either it follows a comma or marker() is inlined; default "in Mimiland".

Value

The first argument rval if any, otherwise NULL.

Details

Mainly useful for the side effect of the message, which can be used to distinguish among versions of the function under development. Can only be used within a function and may be inlined in a <piped sequence> using |>, see examples.

See also

sys.call()

Other utils: const(), endstop(), op-min-max, revmat()

Examples

f1 <- function() marker()
f1()
#> f1 running in Mimiland 

f2 <- function() marker(msg = "in BitsnBobs")
f2()
#> f2 running in BitsnBobs 

f3 <- function() marker(, "in BitsnBobs")
f3()
#> f3 running in BitsnBobs 

## Use inline in "piped" sequence
f4 <- function(x) x |> marker() |> sqrt()
f4(9)
#> f4 running in Mimiland 
#> [1] 3

f5 <- function(x) x |> marker(msg = "inlined in BitsnBobs") |> exp()
f5(1)
#> f5 running inlined in BitsnBobs 
#> [1] 2.718282

f6 <- function(x) x |> marker("inlined in BitsnBobs") |> log()
f4(1) |> f5() |> f6()
#> f6 running inlined in BitsnBobs 
#> f5 running inlined in BitsnBobs 
#> f4 running in Mimiland 
#> [1] 1

rm_objects(f, 1:6)
#> Objects matching "f…" found in (unnamed) environment: –
#> 	 f1 f2 f3 f4 f5 f6 
#> Objects matching "f…" remaining in (unnamed) environment: –
#> 	 All gone!