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package interpreter
import (
"reflect"
"github.com/mvertes/parscan/compiler"
"github.com/mvertes/parscan/scanner"
"github.com/mvertes/parscan/vm"
)
const debug = true
// Interpreter represents the state of an interpreter.
type Interpreter struct {
*compiler.Compiler
*vm.Machine
}
// NewInterpreter returns a new interpreter state.
func NewInterpreter(s *scanner.Scanner) *Interpreter {
return &Interpreter{compiler.NewCompiler(s), &vm.Machine{}}
}
// Eval interprets a src program and return the last produced value if any, or an error.
func (i *Interpreter) Eval(src string) (res reflect.Value, err error) {
codeOffset := len(i.Code)
dataOffset := 0
if codeOffset > 0 {
// All data must be copied to the VM the first time only (re-entrance).
dataOffset = len(i.Data)
}
i.PopExit() // Remove last exit from previous run (re-entrance).
t, err := i.Parse(src)
if err != nil {
return res, err
}
if err = i.Codegen(t); err != nil {
return res, err
}
i.Push(i.Data[dataOffset:]...)
i.PushCode(i.Code[codeOffset:]...)
if s, ok := i.Symbols["main"]; ok {
i.PushCode(vm.Instruction{Op: vm.Calli, Arg: []int{int(i.Data[s.Index].Data.Int())}})
}
i.PushCode(vm.Instruction{Op: vm.Exit})
i.SetIP(max(codeOffset, i.Entry))
if debug {
i.PrintData()
i.PrintCode()
}
err = i.Run()
return i.Top().Data, err
}
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