53 lines
1.1 KiB
Go
53 lines
1.1 KiB
Go
// Copyright (c) 2024-2026 Celestino Amoroso (celestino.amoroso@gmail.com).
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// All rights reserved.
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// operator-fact.go
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package expr
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import (
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"fmt"
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"git.portale-stac.it/go-pkg/expr/kern"
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"git.portale-stac.it/go-pkg/expr/scan"
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)
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//-------- fact term
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func newFactTerm(tk *scan.Token) (inst *scan.Term) {
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return &scan.Term{
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Tk: *tk,
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Children: make([]*scan.Term, 0, 1),
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Position: scan.PosPostfix,
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Priority: scan.PriFact,
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EvalFunc: evalFact,
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}
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}
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func evalFact(ctx kern.ExprContext, opTerm *scan.Term) (v any, err error) {
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var leftValue any
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if leftValue, err = opTerm.Children[0].Compute(ctx); err != nil {
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return
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}
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if kern.IsInteger(leftValue) {
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if i, _ := leftValue.(int64); i >= 0 {
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f := int64(1)
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for k := int64(1); k <= i; k++ {
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f *= k
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}
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v = f
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} else {
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err = fmt.Errorf("factorial of a negative integer (%d) is not allowed", i)
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}
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} else {
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err = opTerm.Errorf("incompatible type for factorial: %s", kern.TypeName(leftValue))
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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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scan.RegisterTermConstructor(scan.SymExclamation, newFactTerm)
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}
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