support signum function on interpolation

[jfromaniello]

I have found that most of my cases where I need iterators can be solve with count.index and some math function given a length (modulo is quite useful!).

signum can be useful in the following scenario:

variable "r53_failover_policy" {
    value = "PRIMARY,FAILOVER"
}

resource "aws_route53_record" "rec" {
    count    = "${var.servers}"
    ...
    failover = "%{element(split(",", var.r53_failover_policy), signum(count.index))}"
}

Given than signum returns 0 for 0 and 1 for every positive number, this means that the first one will have PRIMARY the rest will be FAILOVER. This pattern is quite useful for other resources as well.

[radeksimko]

Implemented in #4854

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.