keywordpkg.go

// Copyright (c) 2022, Peter Ohler, All rights reserved.

package slip

import (
	"strings"
)

// KeywordPkg is the KEYWORD package.
var (
	keywordPkg *Package
	KeywordPkg = Package{
		Name:      "keyword",
		Nicknames: []string{},
		Doc:       "Home of keyword symbols.",
		vars:      map[string]*VarVal{},
		lambdas:   map[string]*Lambda{},
		funcs:     map[string]*FuncInfo{},
		PreSet:    keywordPreSet,
	}
)

func init() {
	KeywordPkg.Initialize(map[string]*VarVal{
		":yes":              {Val: Symbol(":yes"), Const: true, Export: true},
		":no":               {Val: Symbol(":no"), Const: true, Export: true},
		"*keyword-package*": {Val: &KeywordPkg, Const: true, Export: true},
	})
	AddPackage(&KeywordPkg)
	UserPkg.Use(&KeywordPkg)
	keywordPkg = &KeywordPkg
}

func keywordPreSet(p *Package, name string, value Object) (string, Object) {
	if len(name) == 0 {
		PackagePanic(NewScope(), 0, keywordPkg, "An empty symbol is not a valid keyword.")
	}
	if name[0] != ':' {
		name = ":" + name
	}
	name = strings.ToLower(name)
	if vv, has := p.vars[name]; has {
		if ObjectEqual(value, vv.Val) {
			return name, value
		}
		PackagePanic(NewScope(), 0, keywordPkg, "%s is a constant and thus can't be set", name)
	}
	value = Symbol(name)

	return name, value
}