gen

type Backend interface {
	// Infer declares the variables of cell i (Context.Declare), or defers it
	// (Context.Defer), and marks it done (Context.Done).
	Infer(c *Context, i int)

	// Write writes cell k's function, named Context.FuncName(k), whose
	// parameter is a *_nb.Cell: see Ruby's in ruby.go.
	Write(c *Context, b *strings.Builder, k int)

	// Runtime is the import name the generated program gives the language's
	// package (analysis.Runtime), and the declarations that follow the
	// program's variables.
	Runtime() (importName, prelude string)
}

type Code struct {
	Source string
	Line   int
	// Lang is the cell's language: "go" (or ""), "ruby" or "julia".
	Lang string
}

type Context struct {
	// contains filtered or unexported fields
}

type Diag struct {
	Cell      int // -1 when it is not inside a cell
	Line, Col int // in the notebook
	Msg       string
}

type Options struct {
	// RubyTypes maps a Ruby cell's variable to the Go type its value had the
	// last time the cell ran, as the cells package names it
	// ("[]float64", "*{github.com/go-plot/plot}.Figure"). A Go cell sees the
	// variable with that type. A variable not in it is declared any, and the
	// Go cells that read it are deferred until it is known.
	RubyTypes map[string]string
}

type Program struct {
	Source []byte
	Vars   []Var
	Graph  *analysis.Graph
	// Imports maps every package the program imports (but the runtime) to
	// the name it is imported under.
	Imports map[string]string
	// Diags are the notebook's errors. A program with diagnostics is still
	// returned, but will not compile.
	Diags []Diag
	// Deferred maps a cell that cannot be compiled yet to why: it reads a
	// Ruby cell's variable whose Go type is known only once that cell has
	// run (see Options.RubyTypes). It is emitted as a stub that says so.
	Deferred map[int]string
}

type Var struct {
	Name string
	Type string // Go syntax, qualified with the program's import names
	Cell int
	// Ruby marks a Ruby cell's variable. Its Go holder is named Ident when
	// its name is no Go identifier (len, type): Go cells do not see it.
	Ruby  bool
	Ident string
}