Json Lang

Do you want to program in JSON? This simple executor allows you to do that.

Constuctions

The instruction block is an JSON array. It can list instructions that will be performed sequentially. The last operation is the result of the block expression. If the block is empty, then the result is nil.

[]

Numbers are just JSON numbers:

12

To read a variable specify a regular JSON string. If the variable is not set, then it has the value nil.

"x"

To create a string, you need to specify the str key:

{ "str": "hello" }

The let block allows you to assign names to values:

{
    "let": {
        "x": 1,
        "y": 2
    }
}

Variables have their scope limited of a function call or global scope. So, creating a new variable inside a function will not change a more global variable.

To print a value, specify the print key:

{
    "print": { "str": "Hello, World!" }
}

Arithmetic operators like +, -, *, / or the comparison operator == can be expressed as:

{ "+": [12, "x"] }

The result of this expression will be a sum of value 12 and the variable x. If an operation cannot be evaluated, its value will be nil. Note that the JSON array here is not a block of instructions, but simply a short notation of two operans instead of { "left": 12, "right": "x" }.

How to create a function? Just:

{ "fn": 7 }

This creates an anonymous function that returns 7. Let's call it by passing an empty map of parameters, since this function does not take any arguments:

{
    "call": { "fn": 7 },
    "pars": {}
}

The call key specifies a function to call. The pars key specifies a function parameters, if it's empty then the key can be omitted.

What if you need to give a name to a function? So, let's use the let block:

{
    "let": {
        "function_name": { "fn": 7 }
    }
}

Then call it by name:

{ "call": "function_name" }

Good. Let's write some more complex calculation. For example, calculate 1 + x:

{
    "fn": { "+": [1, "x"] }
}

If you simply call this function without parameters, then the value of x will be determined in an outer scope. But we can set this value when calling by passing it as a parameter:

{
    "call": {
        "fn": { "+": [1, "x"] }
    },
    "pars": { "x": 2 }
}

The conditional operator will return the then value if the if value is non-zero or non-empty string, otherwise else:

{
    "if": { "==": [1, 1] },
    "then": 1,
    "else": 2
}