syntax.md

MLang Syntax

Calling a Machine

Calling a machine is indicated by the key starting with a $ followed by the machine path.

The key $Math.add implies:

• The machinepack is machinepack-math, thus var Math = require('machinepack-math')
• Math.add is the machine to be executed

The value is the inputs to the machine.

Let's say we want something like this:

var Math = require('machinepack-math');
Math.add({
  a: 2,
  b: 2
}).exec({
  success: function(result) {
    console.log(result); // result = 4
  }
});

Our MLang program would be:

{
  "$Math.add": {
    "a": 2,
    "b": 2
  }
}

Or more completely:

var mlang = require('machinepack-mlang');
mlang.execute({
  program: {
    "$Math.add": {
      "a": 2,
      "b": 2
    }
  }
}).exec({
  success: function(result) {
    console.log(result); // result = 4
  }
});

Using Input Variables

Using an input variable is indicated by a prefix $ followed by the input variable name.

The following MLang program has the variable x:

{
  "$Math.add": {
    "a": "$x",
    "b": 1
  }
}

A complete example:

var mlang = require('machinepack-mlang');
mlang.execute({
  program: {
    "$Math.add": {
      "a": "$x",
      "b": 1
    }
  },
  inputs: {
    x: 2
  }
}).exec({
  success: function(result) {
    console.log(result); // result = 3
  }
});

Nested Machine Calls

Here's a basic MLang program which results in 5:

{
  "$Arrays.length": {
    "array": [1, 2, 3, 4, 5]
  }
}

Instead of using Arrays.length to count the length of a predefined array we can calculate the length of an array that is the result of another machine call, which can be asynchonous!

Let's try counting the number of GitHub repositories we have:

var mlang = require('machinepack-mlang');
mlang.execute({
  "program": {
    "$Arrays.length": {
      "array": {
        "$Github.listRepos": {
          "owner": "$username"
        }
      }
    }
  },
  "inputs": {
    "username": "Glavin001"
  }
}).exec({
  success: function(result) {
    console.log(result); // result = 30
  }
});

Another example:

var mlang = require('machinepack-mlang');
mlang.execute({
  "program": {
    "$Dictionaries.dot": {
      "dictionary": {
        "$Github.getUserDetails": {
          "user": "$username"
        }
      },
      "keypath": "numFollowers"
    }
  },
  "inputs": {
    "username": "Glavin001"
  }
}).exec({
  success: function(result) {
    console.log(result); // result = 160
  }
});

Advanced Features

Recursion

A machine call with key $this will be recursive.

{
  "$this": {
    "x": 1
  }
}

Exits

Machine inputs with keys starting with @ are exits.

if (x === 0) {
  return true;
} else {
  return false;
}

Is equivalent to the following MLang program:

{
  "$IfThen.ifEqual": {
      "a": "$x",
      "b": 0,
      "@success": true,
      "@otherwise": false
  }
}

Example

Here is an example Fibonacci number program in MLang.

var mlang = require('machinepack-mlang');
mlang.execute({
  "program": {
    "$IfThen.ifEqual": {
      "a": "$x",
      "b": 0,
      "@success": 0,
      "@otherwise": {
        "$IfThen.ifEqual": {
          "a": "$x",
          "b": 1,
          "@success": 1,
          "@otherwise": {
            "$Math.add": {
              "a": {
                "$this": {
                  "x": {
                    "$Math.subtract": {
                      "a": "$x",
                      "b": 1
                    }
                  }
                }
              },
              "b": {
                "$this": {
                  "x": {
                    "$Math.subtract": {
                      "a": "$x",
                      "b": 2
                    }
                  }
                }
              }
            }
          }
        }
      }
    }
  },
  "inputs": {
    "x": "6"
  }
}).exec({
  success: function(result) {
    console.log(result); // result = 8
  }
});