terraform-provider-google/examples/example-versioned-module/ip/variables.tf

variable "name" {
  description = "A name for the ip address resource"
}

variable "labels" {
  type        = "map"
  description = "A map of key:value labels to apply to the ip address resource"
  default     = {}
}

locals {
  # This ends up being a boolean
  # 1 if there are any entries
  # 0 otherwise
  has_labels = "${min(1, length(var.labels))}"
}