Pod count evaluation

[shinae-woo]

Support arithmetic evaluation for PodCount in RegisterObj

e.g.,

• "{{.parallelism}} * 2"
• "{{.parallelism}} * {{.replicas}}"

[dmitsh]

I was wondering if the use of FuncMap would be more intuitive for users.
For example, we define math functions:

func add(a, b int) int {return a + b}
func subtract(a, b int) int {return a - b}
func multiply(a, b int) int {return a * b}
func divide(a, b int) int {
   if b == 0 {
        return 0
    }
    return a / b
}

Then we use them in templates:

funcMap := template.FuncMap{
    "add":      add,
    "sub": subtract,
    "mul": multiply,
    "div":   divide,
}

template.New("submit").Funcs(funcMap).Parse(tmpl)

And the template will look like

{{ mul .A .B }}

[lalitadithya]

I was wondering if the use of FuncMap would be more intuitive for users.
For example, we define math functions:

func add(a, b int) int {return a + b}
func subtract(a, b int) int {return a - b}
func multiply(a, b int) int {return a * b}
func divide(a, b int) int {
   if b == 0 {
        return 0
    }
    return a / b
}

Then we use them in templates:

funcMap := template.FuncMap{
    "add":      add,
    "sub": subtract,
    "mul": multiply,
    "div":   divide,
}

template.New("submit").Funcs(funcMap).Parse(tmpl)

And the template will look like

{{ mul .A .B }}

We don't have to implement this, there already exists a library that provides what you have suggested -- https://github.com/Masterminds/sprig. It's the templating library that's used by helm and I believe some of our internal tools as well. Another advantage of using this library is that users get much more than the basic mathematical operations and not to mention the library is battle tested.

With that said, both approaches (the one in implemented in this PR and the one suggest in this comment) achieve the same end result for this use case but take different approaches.

My question is do we have use cases where users need to use more than just mathematical expressions? Because, if we don't then IMO we can stick to simple mathematical expression evaluation as used in the current approach.

[shinae-woo]

Multiple templates, such as Helm or Hugo, implement mathematical evaluations. The reason that I picked the current implementation was that

• The only requirement, so far, is supporting PodCount and simple mathematical evaluation
• Users don't need to learn a new syntax
• Minimal code footprint

If we have other requirements beyond the current implementation, we can discuss them further, so please let me know if we have any. However, in such case, I would pick one existing implementation rather than introduce and implement our own template.

review