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args_walker.go
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args_walker.go
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package eval
import "github.com/elves/elvish/parse"
type argsWalker struct {
cp *compiler
form *parse.Form
idx int
}
func (cp *compiler) walkArgs(f *parse.Form) *argsWalker {
return &argsWalker{cp, f, 0}
}
func (aw *argsWalker) more() bool {
return aw.idx < len(aw.form.Args)
}
func (aw *argsWalker) peek() *parse.Compound {
if !aw.more() {
aw.cp.errorpf(aw.form.End(), aw.form.End(), "need more arguments")
}
return aw.form.Args[aw.idx]
}
func (aw *argsWalker) next() *parse.Compound {
n := aw.peek()
aw.idx++
return n
}
// nextIs returns whether the next argument's source matches the given text. It
// also consumes the argument if it is.
func (aw *argsWalker) nextIs(text string) bool {
if aw.more() && aw.form.Args[aw.idx].SourceText() == text {
aw.idx++
return true
}
return false
}
// nextMustLambda fetches the next argument, raising an error if it is not a
// lambda.
func (aw *argsWalker) nextMustLambda() *parse.Primary {
n := aw.next()
if len(n.Indexings) != 1 {
aw.cp.errorpf(n.Begin(), n.End(), "must be lambda")
}
if len(n.Indexings[0].Indicies) != 0 {
aw.cp.errorpf(n.Begin(), n.End(), "must be lambda")
}
pn := n.Indexings[0].Head
if pn.Type != parse.Lambda {
aw.cp.errorpf(n.Begin(), n.End(), "must be lambda")
}
return pn
}
func (aw *argsWalker) nextMustLambdaIfAfter(leader string) *parse.Primary {
if aw.nextIs(leader) {
return aw.nextMustLambda()
}
return nil
}
func (aw *argsWalker) mustEnd() {
if aw.more() {
aw.cp.errorpf(aw.form.Args[aw.idx].Begin(), aw.form.End(), "too many arguments")
}
}