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Call-stack

This datapack provides some bare bones support for a call stack like data structure, providing scope to your function files variables. Very convenient for avoiding side effects from other function files overwriting variable values.

Installation

  1. Navigate to the Releases tab and download the latest .zip for this datapack.
  2. Place this datapack in your world's datapacks folder.
  3. Add call_stack:load before your datapack's load function in the Lantern Load load.json tag at your_pack/data/load/tags/functions/load.json.

Usage

Scoping function variables

  1. Wrap function content in the two functions call_stack:push and call_stack:pop.

    # myfunct.mcfunction
function call_stack:push

# your commands here

function call_stack:pop

  2. Create and modify storage variables at call_stack: this.<var-name> without worrying about side affects from other functions (that also implement call_stack).

    # myfunct.mcfunction
function call_stack:push

data modify storage call_stack: this.items set from entity @s Inventory

# call function that may also set this.items
function mypack:otherfunct

# this.items will remain the same here

function call_stack:pop

Passing Arguments to Functions

Data can be passed from caller to callee functions by setting storage at call_stack: call.<var-name>. The callee will then have correspondnig this.<var-name> to access. By convention arg0,arg1...argN variables are used to pass data from caller to callee functions. Note: call.return is restricted since this value is used for function returns.

# myfunct.mcfunction (caller)
function call_stack:push

data modify storage call_stack: call.arg0 set value "foo"
function mypack:otherfunct

function call_stack:pop
# otherfunct.mcfunction (callee)
function call_stack:push

# set a local variable from the this.arg0
data modify storage call_stack: this.thing set from storage call_stack: this.arg0

# your commands

function call_stack:pop

Function Return Values

Return data from a function by setting the storage call_stack: this.return. This value will be copied into caller functions scope at call_stack: call.return.