/
environment.go
58 lines (50 loc) · 1.12 KB
/
environment.go
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package interpreter
import "errors"
var (
ErrAlreadyDefined = errors.New("The name is already defined in this scope.")
ErrUndefined = errors.New("Undefined name.")
)
type Environment struct {
parent *Environment
names map[string]any
nestingLevel int
}
func NewEnvironment(parent *Environment) *Environment {
nestingLevel := 0
if parent != nil {
nestingLevel = parent.nestingLevel + 1
}
return &Environment{
parent: parent,
names: make(map[string]any),
nestingLevel: nestingLevel,
}
}
func (e *Environment) Define(name string, value any) error {
if name == "" {
return nil
}
if e.Exists(name) {
return ErrAlreadyDefined
}
e.names[name] = value
return nil
}
func (e *Environment) Assign(name string, value any, nestingLevel int) {
env := e
for nestingLevel != env.nestingLevel {
env = env.parent
}
env.names[name] = value
}
func (e *Environment) Get(name string, nestingLevel int) any {
env := e
for nestingLevel != env.nestingLevel {
env = env.parent
}
return env.names[name]
}
func (e *Environment) Exists(name string) bool {
_, ok := e.names[name]
return ok
}