69 lines
1.5 KiB
Go
69 lines
1.5 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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import "fmt"
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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 verifyIndex(indexTerm *term, indexValue any, maxValue int) (index int, err error) {
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var v int
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if v, err = indexTerm.toInt(indexValue, "index expression value must be integer"); err == nil {
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if v >= 0 && v < maxValue {
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index = v
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} else if index >= -maxValue {
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index = maxValue + v
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} else {
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err = indexTerm.Errorf("index %d out of bounds", v)
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}
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}
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return
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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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switch unboxedValue := leftValue.(type) {
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case []any:
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var index int
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if index, err = verifyIndex(indexTerm, rightValue, len(unboxedValue)); err == nil {
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v = unboxedValue[index]
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}
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case string:
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var index int
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if index, err = verifyIndex(indexTerm, rightValue, len(unboxedValue)); err == nil {
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v = unboxedValue[index]
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}
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case map[any]any:
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var ok bool
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if v, ok = unboxedValue[rightValue]; !ok {
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err = fmt.Errorf("key %v does not belong to the dictionary", rightValue)
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}
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default:
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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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