Internals
Expr is a stack-based virtual machine. It compiles expressions to bytecode and runs it. The compilation is done in a few steps:
- Parse expression to AST
- Type check AST
- Apply operator overloading
- Apply custom AST patching
- Optimize AST
- Compile AST to a bytecode
The compiler has a bunch of optimization which will produce a more optimal program.
In array
value in ['foo', 'bar', 'baz']
If Expr finds an in or not in expression with an array, it will be
transformed into:
value in {"foo": true, "bar": true, "baz": true}
Constant folding
Arithmetic expressions with constants are computed on compile step and replaced with the result.
-(2 - 5) ** 3 - 2 / (+4 - 3) + -2
Will be compiled into just a single number:
23
In range
user.Age in 18..32
Will be replaced with a binary operator:
18 <= user.Age && user.Age <= 32
Const range
1..10_000
Ranges computed on the compile stage, are replaced with pre-created slices.
Const expr
If some function is marked as a constant expression with expr.ConstExpr. It will be
replaced with the result of the call if all arguments are constants.
expr.ConstExpt("fib")
fib(42)
Will be replaced with the result of fib(42)` on the compile step.