Internal term *score calculator* denotes algorithm, which is responsible for computing overall score (correctness) of a submitted solution from the results of individual solution test. Each exercise is given a calculator name and associated calculator configuration (stored in DB text column as Yaml), which is used to initialize/prepare the calculator before it is used for computing the score.
We have implemented three calculators so far:
## Uniform
Trivial algorithm, which computes the overall score as arithmetic average of individual test scores. This calculator has no configuration.
## Weighted
Computes overall score as weighted average of individual test scores. The calculator expects that the weights are stored in the configuration in the following format:
The keys are test names (must correspond with the `name` column of the `exercise_test`) and the values has to be integers. When all weights are equal, the weighted calculator behaves exactly as uniform calculator.
The most complex calculator which was added last. It holds an AST (Abstract Syntax Tree) of an expression used to compute the score in the configuration.
The AST is encoded directly into Yaml structure -- each node is represented as a collection (object). A node must always have property `type`, which holds a string identifier of the node type (types of nodes are below).
Leaf nodes (without children):
*`value` - a literal value, which holds one float (the value itself is stored in `value` property)
*`test-result` - reference to a test score, which is also a float between 0 and 1 (name of the test is in the `test` property)
