cat in nimbleFunction run-code imitates the R function cat. It prints its arguments in order. No newline is inserted, so include "\n" if one is desired.
When an uncompiled nimbleFunction is executed, R's cat is used. In a compiled nimbleFunction, a C++ output stream is used that will generally format output similarly to R's cat. Non-scalar numeric objects can be included, although their output will be formatted slightly different in uncompiled and compiled nimbleFunctions.
In nimbleFunction run-time code, cat is identical to print except the latter appends a newline at the end.
nimCat is the same as cat, and the latter is converted to the former when a nimbleFunction is defined.
For numeric values, the number of digits printed is controlled by the system option nimbleOptions('digits').