Fix statement vs expr

[jakzale]

Fixes #51, #54

Essentially we make [Statement f] as our program and the main parsing rule.

• Fix Sign vs Sig naming issue,
• add Statements f newtype for [Statement f]
• add Program f newtype of Statements f as top-level node of AST.
• duplicate necessary functions with
  • stmt prefix for statements, and
  • expr prefix for expressions.
• update and clean up all the test cases.
• add stack bench for testing the generators.

In addition we add the benchmark of quickcheck generators

[jakzale]

@effectfully, I added a benchmark (stack bench) for testing the generators.

Does the following output looks good to you?

Requested runs:  1000
Requested size:  1000

Minimum depth = 0
Maximum depth = 15
Mean depth    = 3.168

Minimum number of nodes = 0
Maximum number of nodes = 1890
Mean number of nodes    = 565.964

[effectfully]

Does the following output looks good to you?

Yes. We'll need some more refined tool to output other interesting stats (how many adds, muls etc there are, how many variables the program has, how many of them are mentioned at least twice, how many comparisons are done on "negative integers", etc).

We'll also need to see if it makes the compiler tests slower, 'cause they are already quite slow.

But for now looks good.

[effectfully]

I'll review the generators stuff a bit later.

[jakzale]

There are some issues with ProgramWithEnv arbitrary instances:

        *** Failed! (after 4 tests and 1 shrink):
        evaluation of renamed program
        [Some 16,Some (UniConst Bool False),Some 1]
        differs from evaluation of original program
        [Some (UniConst Bool False),Some 16]
        for final state of renamed program
        Right (Env {unEnv = fromList [(0,Some 16),(9,Some (UniConst Bool False)),(23,Some 1)]})
        for final state of evaluated program
        Right (Env {unEnv = fromList [(9,Some (UniConst Bool False)),(23,Some 16)]})
        for renamed program
        let u_0 = 16;
        
        for original program
        let u_23 = 16;
        
        ProgramWithEnv (Program (Statements [ELet (UniVar {_uniVarUni = Field, _uniVarVar = u_23}) (EConst 16)])) (Env {unEnv = fromList [(9,Some (UniConst Bool False)),(23,Some 1)]})

[jakzale]

I suspect there will be a test error, but it will be tied to #76 due to lack of assignments and proper typing environments.

[effectfully]

Ok, let's get this in!

[effectfully]

As per previous discussion we already know in the otherwise clause that start > end and hence can do withVar var start kont there instead, but not a big deal.