exists - Check whether a variable exists
Determines whether the RevBayes workspace contains a variable named 'name'
||String (pass by value)
|The name of the variable we wish to check for existence.
'exists' returns 'true' if the workspace contains a variable whose name matches the String 'name' and 'false' otherwise. One use of 'exists' is to add Move and Monitor objects conditional on the variable 'x' existing. The function 'ls' provides a summary for all variable names that 'exists' would evaluate as 'true'.
## Correct usage: does "x" exist?
x <- 1.0
## Incorrect usage: does "1.0" exist?