Code Representation Using JSON Arrays

In Calcium, a program to output "Hello, World." looks like this:

[
  [
    1,      // Block level. Same as the depth of indentation in Python.
    [],     // Arbitrary elements. Currently unused.
    "expr", // Command name. Indicates what type of statement is being executed. This example is an "expression statement."
    ["call", ["var", "print"], ["Hello, World."]] // Command arguments. Explained later.
  ],
  [1, [], "end"] // The program must end with the "end" command.
]

The equivalent Python code is:

print("Hello, World.")

Block Level

In the following Python code, the control statement increases the indentation by one level:

if answer is 42:
    pass

In Calcium's JSON array, the leading integer represents this indentation level:

[1, [], "ifs"],
  [2, [], "if", ["is", ["var", "answer"], ["num", "42"]]],
    [3, [], "pass"],
[1, [], "end"]

Whitespace in JSON is meaningless, so indentation is represented by integers.

Commands

In Calcium, each statement is treated as a "command." Examples include if, for, and while.
Basic Python statements are supported.

Expressions

Expressions in Calcium are slightly unique. They take the form of arrays, with the first element indicating the type.
For example, a variable is represented as ["var", "answer"].