Implement the exercise "high-scores" about c HOT 9 CLOSED

An opaque type is another thing that I wouldn't call "easy". And if you consider dynamic memory allocation (and deallocation), pointers as output parameters, and opaque types as easy then (almost) all exercises on the C track are easy.
I've asked on the forum if somebody has ideas.

BTW: Whether you want to call the type alias table or TABLE is IMHO a minor detail (although I always try to reserve identifiers in "ALL_CAPS" for the preprocessor).

from c.

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from c.

I did play with this exercise a little bit and did not see a way for a straightforward translation.

In the original tests there's some "object" that gets initialized with a number of scores, and there are three four methods:

• scores() returns all the scores (a array, in the original order), and
• latest() returns the most recent score (a number),
• personalBest() returns the highest score.
• personalTopThree() returns the three highest scores (an array, in non-ascending order).

The "comments" at the beginning of the canonical-data.json say:

This is meant to be an easy exercise to practise:

• arrays as simple lists
• instantiating a class

I don't see a way to keep the solution simple and uses arrays and use some kind of class.

If I'd want to keep the exercise simple I would require two three independent functions that take some scores: latest(scores, scores_len) would return the last element of scores, personal_best(scores, scores_len) would return the greatest element of scores, personal_top_three(scores, scores_len, &result) would write the three highest scores to the output variable result, and scores() wouldn't make sense at all because it would just return its argument.

If I'd want personal_top_three() (and maybe scores()) to "return" an array I would either need one or two output-parameters (because I would need to communicate the array and its length to the caller), or I'd have to create a struct that holds the array and its length. And the array might need to be dynamically allocated and later deallocated.

If I'd want to have some class-like structure I'd have to take care of the lifetimes of the arrays, maybe copy or allocate/deallocate them.

Do you have an idea how to keep the C translation close in line with the tests and objectives ("easy", "arrays", "class")?

[edited, i forgot one of the four functions]

from c.

To honour the 'class' objective, we can use an opaque data type:

struct table_impl;
typedef struct table_impl* table;

table create_table(int* scores, size_t scores_len);
int latest(table t);
int personal_best(table t);
size_t personal_top_three(table t, int* dest);
void destroy_table(table t);

#include "high_scores.h"

struct table_impl {
};

scores() is omitted as it is not 'easy'.

from c.

As most students will be familiar with the use of FILE*, it might be better to use

struct table;
typedef struct table TABLE;

TABLE* create_table( . . . );

#include "high_scores.h"

struct table {
};

from c.

We can omit the 'class' objective, as in Awk and Fortran.

int latest(const int* scores, size_t scores_len);
int personal_best(const int* scores, size_t scores_len);
size_t personal_top_three(const int* scores, size_t scores_len, int* dest);

from c.

We can omit the 'class' objective, as in Awk and Fortran.

I'd be OK with that, I think that might be the simplest option.

from c.

We can omit the 'class' objective, as in Awk and Fortran.

I'd be OK with that, I think that might be the simplest option.

Agreed. Going much further than this approach brings in a lot of complexity.

from c.

PR #902 is ready for review. It was automatically closed.

from c.