move to a direct byte code compiler (#8)

* chore: refactor to keep only the new parser and bytecode vm

* scanner: remove Token.value field

* scanner: remove scanner.kind field

* chore: move language specification in lang package

This avoid a cyclic dependency in scanner_test which can now use
the golang/GoSpec language specification for Go.

* clean code

* scanner: export scanner fields

Also parser now generate function calls, including externals.

* chore: fix lint issues

* parser: handle strings

* wip

* parser: implement support for 'if, else, else if' statements

Resolving labels in the compiler still in progress.

* parser: support if statements, improve compiler

* improve handling of functions

* improve support of local variables

* scanner: trim leading and trailing spaces

* fixes to make fibonacci work

* parser: improve README, fix function parameters parsing

1 files changed, 52 insertions, 0 deletions

diff --git a/parser/interpreter.go b/parser/interpreter.go
new file mode 100644
index 0000000..72fc667
--- /dev/null
+++ b/parser/interpreter.go
@@ -0,0 +1,52 @@
+package parser
+
+import (
+	"github.com/gnolang/parscan/scanner"
+	"github.com/gnolang/parscan/vm"
+)
+
+const debug = true
+
+type Interpreter struct {
+	*Compiler
+	*vm.Machine
+}
+
+func NewInterpreter(s *scanner.Scanner) *Interpreter {
+	return &Interpreter{NewCompiler(s), &vm.Machine{}}
+}
+
+func (i *Interpreter) Eval(src string) (res any, 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:]...)
+	i.PushCode([]int64{0, vm.Exit})
+	i.SetIP(max(codeOffset, i.Entry))
+	if debug {
+		i.PrintData()
+		i.PrintCode()
+	}
+	err = i.Run()
+	return i.Top(), err
+}
+
+func max(a, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}