stack.go

 
/*
Copyright © 2022 Pavel Tisnovsky

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/



package
 
evaluator

Documentation in literate-programming-style is available at: https://redhatinsights.github.io/insights-operator-utils/packages/evaluator/stack.html

 


import
 
(

	
"fmt"


)

Stack struct is naive but fully functional implementation of operand stack

 
type
 
Stack
 
struct
 
{

	
stack
 
[
]
int


}

Push method pushes value onto the stack

 
func
 
(
stack
 
*
Stack
)
 
Push
(
value
 
int
)
 
{

	
stack
.
stack
 
=
 
append
(
stack
.
stack
,
 
value
)


}

Pop method pops value from stack with check if stack is empty

 
func
 
(
stack
 
*
Stack
)
 
Pop
(
)
 
(
int
,
 
error
)
 
{

	
if
 
stack
.
Empty
(
)
 
{

		
return
 
-
1
,
 
fmt
.
Errorf
(
"Empty stack"
)

	
}

index of top of stack (TOS)

 
	
tos
 
:=
 
len
(
stack
.
stack
)
 
-
 
1

read element from the stack

 
	
element
 
:=
 
stack
.
stack
[
tos
]

remove element from the stack

 
	
stack
.
stack
 
=
 
stack
.
stack
[
:
tos
]

	
return
 
element
,
 
nil


}

Empty method checks if the stack is empty

 
func
 
(
stack
 
*
Stack
)
 
Empty
(
)
 
bool
 
{

	
return
 
len
(
stack
.
stack
)
 
==
 
0


}

Size method returns number of items on stack

 
func
 
(
stack
 
*
Stack
)
 
Size
(
)
 
int
 
{

	
return
 
len
(
stack
.
stack
)


}