// Copyright (c) 2020 Alexander Kiryukhin <a.kiryukhin@mail.ru>
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
package executor
import (
"errors"
"fmt"
)
// Calc calculates expressions
type Calc struct {
preparedTokens []*token
functions map[string]*Function
operators map[string]*Operator
}
// NewCalc instantinates new calculator
func NewCalc() *Calc {
c := &Calc{
functions: map[string]*Function{},
operators: map[string]*Operator{},
}
return c
}
// Prepare expression before execution
func (c *Calc) Prepare(expression string) error {
t := newTokenizer(expression, c.operators)
if err := t.tokenize(); err != nil {
return err
}
tkns, err := t.toRPN()
if err != nil {
return err
}
c.preparedTokens = tkns
return nil
}
// Execute prepared expression with variables at `vars` argument
func (c *Calc) Execute(vars map[string]float64) (float64, error) {
if len(c.preparedTokens) == 0 {
return 0, errors.New("must prepare expression")
}
if vars == nil {
vars = map[string]float64{}
}
var stack []float64
for _, tkn := range c.preparedTokens {
switch tkn.Type {
case literalType:
stack = append(stack, tkn.FValue)
case operatorType:
sz := len(stack)
if sz < 2 {
return 0, errors.New("empty stack")
}
var args []float64
args, stack = stack[sz-2:], stack[:sz-2]
if op, ok := c.operators[tkn.SValue]; ok {
res, err := op.Fn(args[0], args[1])
if err != nil {
return 0, err
}
stack = append(stack, res)
} else {
return 0, fmt.Errorf("unknown operator '%s'", tkn.SValue)
}
case functionType:
fn, exists := c.functions[tkn.SValue]
if !exists {
return 0, fmt.Errorf("unknown function '%s'", tkn.SValue)
}
sz := len(stack)
if sz < fn.Places {
return 0, errors.New("not enough args")
}
var args []float64
args, stack = stack[sz-fn.Places:], stack[:sz-fn.Places]
res, err := fn.Fn(args...)
if err != nil {
return 0, err
}
stack = append(stack, res)
case variableType:
res, exists := vars[tkn.SValue]
if !exists {
return 0, fmt.Errorf("unknown variable '%s'", tkn.SValue)
}
stack = append(stack, res)
default:
return 0, fmt.Errorf("unknown token %d, %s, %f", tkn.Type, tkn.SValue, tkn.FValue)
}
}
if len(stack) != 1 {
return 0, errors.New("invalid expression")
}
return stack[0], nil
}
// AddFunction adds custom function
func (c *Calc) AddFunction(cf *Function) {
c.functions[cf.Name] = cf
}
// AddOperator adds custom operator
func (c *Calc) AddOperator(op *Operator) {
c.operators[op.Op] = op
}
// AddFunctions xadds many custom functions
func (c *Calc) AddFunctions(funcs []*Function) {
for _, fn := range funcs {
c.AddFunction(fn)
}
}
// AddOperators adds many custom operators
func (c *Calc) AddOperators(operators []*Operator) {
for _, op := range operators {
c.AddOperator(op)
}
}
