The reject statement has the same syntax as the print statement, accepting an arbitrary number of arguments of any type (including string literals). The effect of executing a reject statement is to throw an exception internally that terminates the current iteration with a rejection (the behavior of which will depend on the algorithmic context in which it occurs).
(T1 x1,..., TN xN)
Reject the current iteration and print the values denoted by the arguments x1 through xN on the output message stream. There are no spaces between items in the print, but a line feed (LF; Unicode U+000A; C++ literal
'\n') is inserted at the end of the printed
line. The types
TN can be any of Stan’s built-in
numerical types or double quoted strings of characters (bytes).
Available since 2.18