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package compiler
type ScopeID int
type ScopeChain struct {
scopes []Scope
}
func NewScopeChain() ScopeChain {
scopes := make([]Scope, 1)
scopes[0] = Scope{
kind: ScopeKindGlobal,
symbols: make(map[string]Symbol),
}
return ScopeChain{
scopes: scopes,
}
}
func (sc *ScopeChain) Current() *Scope {
return &sc.scopes[len(sc.scopes)-1]
}
func (sc *ScopeChain) Enter(kind ScopeKind) {
sc.scopes = append(sc.scopes, Scope{
kind: kind,
symbols: make(map[string]Symbol),
})
}
func (sc *ScopeChain) Exit() {
sc.scopes[len(sc.scopes)-1] = Scope{}
sc.scopes = sc.scopes[:len(sc.scopes)-1]
}
func (sc *ScopeChain) Declare(name string) bool {
// Check whether the symbol is already declared in any of the scopes.
for _, scope := range sc.scopes {
if _, ok := scope.symbols[name]; ok {
return false
}
}
// Declare the symbol in the current scope.
sc.Current().symbols[name] = Symbol{
kind: SymbolKindVariable,
name: name,
localIndex: len(sc.Current().symbols),
}
return true
}
func (sc *ScopeChain) Lookup(name string) (Symbol, bool) {
for i := len(sc.scopes) - 1; i >= 0; i-- {
if symbol, ok := sc.scopes[i].symbols[name]; ok {
return symbol, true
}
}
return Symbol{}, false
}
type ScopeKind int
const (
ScopeKindGlobal ScopeKind = iota
ScopeKindFunction
ScopeKindBlock
)
type Scope struct {
kind ScopeKind
symbols map[string]Symbol
}
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