expr/operand-var.go

// Copyright (c) 2024 Celestino Amoroso (celestino.amoroso@gmail.com).
// All rights reserved.

// operand-var.go
package expr

import "fmt"

// -------- variable term
func newVarTerm(tk *Token) *term {
	return &term{
		tk: *tk,
		// class:    classVar,
		// kind:     kindUnknown,
		parent:   nil,
		children: nil,
		position: posLeaf,
		priority: priValue,
		evalFunc: evalVar,
	}
}

// -------- eval func
func evalVar(ctx ExprContext, self *term) (v any, err error) {
	var exists bool
	name := self.source()
	if v, exists = ctx.GetVar(name); !exists {
		info := ctx.GetFuncInfo(name)
		if info != nil {
			v = info.Functor()
		} else {
			err = fmt.Errorf("undefined variable or function %q", name)
		}
	}
	return
}

// init
func init() {
	registerTermConstructor(SymIdentifier, newVarTerm)
}