63 lines
1.2 KiB
Go
63 lines
1.2 KiB
Go
package main
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import "fmt"
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type Environment struct {
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values map[string]any
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enclosing *Environment
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}
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func newEnvironment(enclosing *Environment) *Environment {
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return &Environment{map[string]any{}, enclosing}
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}
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func (env *Environment) get(key string) any {
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if found, ok := env.values[key]; ok {
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return found
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}
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if env.enclosing != nil {
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return env.enclosing.get(key)
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}
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return nil
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}
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func (env *Environment) exists(key string) bool {
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_, ok := env.values[key]
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return ok
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}
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func (env *Environment) define(key string, val any) {
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env.values[key] = val
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}
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func (env *Environment) assign(key Token, val any) *RuntimeError {
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if env.exists(key.lexeme) {
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env.values[key.lexeme] = val
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return nil
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}
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if env.enclosing == nil {
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return &RuntimeError{key, fmt.Sprintf("Can't assign: undefined variable '%s'.", key.lexeme)}
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}
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return env.enclosing.assign(key, val)
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}
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func (env *Environment) getAt(distance int, key string) any {
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return env.ancestor(distance).get(key)
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}
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func (env *Environment) assignAt(distance int, key Token, val any) {
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env.ancestor(distance).values[key.lexeme] = val
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}
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func (env *Environment) ancestor(distance int) *Environment {
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parent := env
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for i := 0; i < distance; i++ {
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parent = parent.enclosing
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}
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return parent
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}
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