# JuliaVariables

# About

The `solve`

function will solve the scopes of a **simplified** Julia expression.

- The variables(
`Symbol`

) are transformed to`Var`

:struct Var name :: Symbol is_mutable :: Bool is_shared :: Bool is_global :: Bool end

- Some expressions will be wrapped within
`Expr(:scoped, (bounds=..., freevars=..., bound_inits=...), inner_expression)`

.

# Example

`solve`

& `solve_from_local`

```
julia> using MLStyle
julia> unwrap_scoped(ex) =
@match ex begin
Expr(:scoped, _, a) => unwrap_scoped(a)
Expr(head, args...) => Expr(head, map(unwrap_scoped, args)...)
a => a
end
unwrap_scoped (generic function with 1 method)
julia> quote
x = 1
function (a)
x = 1
end
end |> solve_from_local |> rmlines |> unwrap_scoped
quote
mut @shared x = 1
function (a,)
mut @shared x = 1
end
end
julia> quote
x = 1
function ()
x = 1
end
end |> solve |> rmlines
:($(Expr(:scoped, (bounds = Var[], freevars = Var[], bound_inits = Symbol[]), quote
@global x = 1
function ()
$(Expr(:scoped, (bounds = Var[@local x], freevars = Var[], bound_inits = Symbol[]), quote
@local x = 1
end))
end
end)))
julia> quote
x = 1
function ()
x = 1
end
end |> solve_from_local |> rmlines
:($(Expr(:scoped, (bounds = Var[mut @shared x], freevars = Var[], bound_inits = Symbol[]), quote
mut @shared x = 1
function ()
$(Expr(:scoped, (bounds = Var[], freevars = Var[mut @shared x], bound_inits = Symbol[]), quote
mut @shared x = 1
end))
end
end)))
```

`simplify_ex`

Not all expressions can be accepted as the input of `solve`

or `solve_from_local`

, thus we provide such a
handy API to apply conversions from almost arbitrary
expressions to the *simplified* expressions.

```
julia> quote
function f(x)
for i in I, j in J
let x = 1, y
() -> 2
end
end
f(x) = 2
end
end |> rmlines |> simplify_ex
quote
function f(x)
for i = I
for j = J
let x = 1
let y
function ()
2
end
end
end
end
end
function f(x)
2
end
end
end
```

The reason why we don't couple this API with `solve`

is, we need to let user aware that there exists destructive operations for expressing the scope information, for instance, it's impossible to inject
scope information to `for i in I, j in J; body end`

, because
the AST shape of it is

```
Expr(:for,
Expr(:block,
:(i = I),
:(j = J),
),
Expr(:block, body)
)
```

`Expr(:block, body)`

is actually in the sub-scope of
that of `:(j = J)`

, and `:(j=J)`

's scope in inherited from that of `:(i=I)`

, which ruins the handy use(especially the top-down tree visiting) of scoped expressions.

Not only due to the uselessness of scoping the messy ASTs like `for i in I, j in J; body end`

, the analyses for them are also much more ugly to implement than those of the *simplified* expressions. Finally, I give up doing this.

If you have understood the above concerns and made
sure it's safe to return a restructured expression after injecting scope information, you can compose
`simplify_ex`

and `solve`

to gain a more handy API:

```
mysolve! = solve! ∘ simplify_ex
mysolve_from_local! = solve_from_local! ∘ simplify_ex
```