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It appears your OpenWatcom C compiler is defaulting to using C89. In C89 variable declarations must be at the beginning of a block scope. In your case all your code and data is at function scope, so the variable has to be declared at the beginning of main before the code.

Moving the variable declaration this way should be C89 compatible:

bracket v. To bound on both sides, to surround, as enclosing with brackets
    — wiktionary

The thing that bracket does is it wraps some operation that uses a resource with the actions that allocate and deallocate that resource (with some care taken to ensure that deallocation happens even when exceptions are thrown). So the (de)allocation actions surround – or bracket – the main operation.

The file example you mention is especially suggestive. Like "open bracket" for [ or ( and "close bracket" for ] or ), the bracketing actions are "open file" and "close file" (well, "close handle"). This parallel is fairly common; e.g. with databases, one opens and closes a connection, with network stuff, one opens and closes a session, with subprocesses, one opens and closes a program, etc.

The issue you're going to have to confront is how to deal with function calls. I can't really give you any concrete advice based on your question, because the grammar you provide lacks any indication of the intended syntax of functions calls, but the hint that print(5) is a valid statement makes it clear that there are two distinct situations, which need to be handled separately.

Consider:

This

You can do this in O(n²) time by using a two-dimensional array highest_score, where highest_score[i][b] is the highest score achievable after position i with b open brackets yet to be closed. Each element highest_score[i][b] depends only on highest_score[i−1][b−1], highest_score[i−1][b], and highest_score[i−1][b+1] (and of course A[i]), so each row highest_score[i] can be computed in O(n) time from the previous row highest_score[i−1], and the final answer is highest_score[n][0].

(Note: that uses O(n²) space, but since each row of highest_score depends only on the previous row, you can actually do it in O(n) by reusing rows. But the asymptotic runtime complexity will be the same either way.)

That's because for the loc assignment all index axes are aligned, including the columns: Since age and name do not match, there is no data to assign, hence the NaNs.

You can make it work by renaming the columns:

According to https://docs.python.org/3/whatsnew/3.10.html#pep-634-structural-pattern-matching, you use a | between patterns.

It looks like strictly speaking, this doesn't conform with the grammar as specified. But at least, it does make sense for a compiler to allow it: the reason PrimaryNoNewArray is used instead of Primary here is so that an expression like new int[1][0] cannot be ambiguously parsed as either a 2D array or as an array access like (new int[1])[0]. If the array has an initializer like new int[]{0}[0] then the syntax is not ambiguous because this cannot be parsed as creating a 2D array.

That said, since the JLS doesn't specify that it's allowed, it could be treated as either an implementation detail or a bug in the compiler which allows it.