62 lines
1.3 KiB
Go
62 lines
1.3 KiB
Go
// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// operator-dot.go
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package expr
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// -------- dot term
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func newDotTerm(tk *Token) (inst *term) {
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return &term{
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tk: *tk,
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children: make([]*term, 0, 2),
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position: posInfix,
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priority: priDot,
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evalFunc: evalDot,
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}
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}
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func evalDot(ctx ExprContext, self *term) (v any, err error) {
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var leftValue, rightValue any
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if leftValue, rightValue, err = self.evalInfix(ctx); err != nil {
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return
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}
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indexTerm := self.children[1]
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if !isInteger(rightValue) {
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err = indexTerm.Errorf("index expression must be integer, got %T", rightValue)
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return
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}
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index64, _ := rightValue.(int64)
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index := int(index64)
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if isList(leftValue) {
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list, _ := leftValue.([]any)
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if index >= 0 && index < len(list) {
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v = list[index]
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} else if index >= -len(list) {
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v = list[len(list)+index]
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} else {
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err = indexTerm.Errorf("index %v out of bounds", index)
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}
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} else if isString(leftValue) {
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s, _ := leftValue.(string)
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if index >= 0 && index < len(s) {
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v = string(s[index])
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} else if index >= -len(s) {
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v = string(s[len(s)+index])
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} else {
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err = indexTerm.Errorf("index %v out of bounds", index)
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}
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} else {
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err = self.errIncompatibleTypes(leftValue, rightValue)
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}
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return
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}
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// init
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func init() {
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registerTermConstructor(SymDot, newDotTerm)
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}
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