alashworth
commented
5 years ago 
I asked @mitzimorris to file the issue, but wanted to add what we were discussing with @seantalts:
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The operators aren't in either R or Python
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The postfix form in particular has a confusing semantics (as noted in the issue).
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The prefix form will actually change behavior of
--xand++x, which are equal to-(-(x))and+(+(x))and both evaluate tox. Now they are prefix operators. -
The operation is restricted to indexed variables, just like assignments, rather than everything else we have which is restricted to assignments.
The main reason we have n = n + 1 and whatnot in the code is that we are either counting or incremeting some index that isn't tracking the loop indexes.
Summary:
Add the postfix version of the increment operator "++" to Stan language for integer types, which can be in expressions or as a statement, e.g.:
The semantics of the postfix increment operator are:
The same result can be gotten from:
https://github.com/stan-dev/stan/issues/1787, which has been implemented here: https://github.com/stan-dev/stan/tree/feature/1787-compound-assign-ops-scalars
It's not clear we need this feature as well.
Description:
The "++" operator is useful when incrementing (and decrementing) counters.
Both Java and C++ (hence the name) support this operator. However R and Python don't. Java and C++ have both prefix and postfix versions of this operator, with different semantics.
Current Version:
v2.15.0