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