Partial eval

[nwokafor-choongsaeng]

Terms

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[nwokafor-choongsaeng]

The Interpreter has been modified to allow configurations to it. The only configuration right now is turning on partial evaluation and this is done by setting the allowPartial to true in the config. Two config values, complete and partial, are added for convenience as well.

Partial evaluation allows the interpreter to evaluate parts of a value that can be evaluated, while preserving the parts that cannot.

Note

1. If-else will try to pick a branch. If it finds a condition that holds true, then it selects that branch and evaluates. Likewise, it discards a branch when it's condition is false. Otherwise, it will preserve the if-else structure if it contains conditions that were partially evaluated.
2. A pattern match will always be preserved because it could contain a catch-all pattern that will always match whereas the target was only partially evaluated.

An improvement was also added to the interpreter because it previously didn't evaluate variable values that were looked-up from the state.

Partial Evaluation Example

1 + 2 + var = 3 + var

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if 1 == 1 then 2 else if var == 2 then 3 else 4
evaluates to 
2

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if 1 == 2 then 1 else if var == 2 then 3 else 4
evalutates to
if var == 2 then 3 else 4