83 lines
1.9 KiB
Go
83 lines
1.9 KiB
Go
// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// operator-coalesce.go
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package expr
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//-------- null coalesce term
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func newNullCoalesceTerm(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: priCoalesce,
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evalFunc: evalNullCoalesce,
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}
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}
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func evalNullCoalesce(ctx ExprContext, self *term) (v any, err error) {
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var rightValue any
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if err = self.checkOperands(); err != nil {
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return
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}
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leftTerm := self.children[0]
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if leftTerm.tk.Sym != SymVariable {
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err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
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return
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}
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if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
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v = leftValue
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} else if rightValue, err = self.children[1].compute(ctx); err == nil {
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v = rightValue
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}
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return
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}
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//-------- coalesce assign term
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func newCoalesceAssignTerm(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: priCoalesce,
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evalFunc: evalAssignCoalesce,
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}
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}
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func evalAssignCoalesce(ctx ExprContext, self *term) (v any, err error) {
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var rightValue any
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if err = self.checkOperands(); err != nil {
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return
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}
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leftTerm := self.children[0]
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if leftTerm.tk.Sym != SymVariable {
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err = leftTerm.Errorf("left operand of %q must be a variable", self.tk.source)
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return
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}
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if leftValue, exists := ctx.GetVar(leftTerm.source()); exists {
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v = leftValue
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} else if rightValue, err = self.children[1].compute(ctx); err == nil {
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if functor, ok := rightValue.(Functor); ok {
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ctx.RegisterFunc(leftTerm.source(), functor, 0, -1)
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} else {
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v = rightValue
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ctx.UnsafeSetVar(leftTerm.source(), rightValue)
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}
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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(SymDoubleQuestion, newNullCoalesceTerm)
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registerTermConstructor(SymQuestionEqual, newCoalesceAssignTerm)
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}
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