math

Commentary

added in 0.7.3

Evaluates an infix mathematical string expression. This is handy if you have a long formula and don't want to write out nested ShadowTraffic function calls. You can access variables directly by name.

In other words, you can write this:

{
    "_gen": "math",
    "expr": "(2 + 4) * 3"
}

Instead of this:

{
    "_gen": "multiply",
    "args": [
        {
            3,
            {
                "_gen": "add",
                "args": [
                    2, 4
                ]
            }
        }
    ]
}

Expressions are parsed and compiled ahead of time, meaning performance should be similar to using the rest of ShadowTraffic's math functions directly.

Available functions

• abs(x): absolute value
• acos(x): arc cosine
• asin(x): arc sine
• atan(x): arc tangent
• cbrt(x): cubic root
• ceil(x): nearest upper integer
• cos(x): cosine
• cosh(x): hyperbolic cosine
• exp(x): euler's number raised to the power (e^x)
• floor(x): nearest lower integer
• log(x): logarithmus naturalis (base e)
• log10(x): logarithm (base 10)
• log2(x): logarithm (base 2)
• max(a, b): maximum of a and b
• min(a, b): minimum of a and b
• pow(x, y): raises x to the power of y
• sin(x): sine
• sinh(x): hyperbolic sine
• sqrt(x): square root
• tan(x): tangent
• tanh(x): hyperbolic tangent
• signum(x): signum function

---

Examples

Calculating constants

Use expr to supply a math expression. Use any of the available functions listed above with arbitrary nesting.

{
    "_gen": "math",
    "expr": "2 + (log(4) * cos(10))"
}

[
    0.8367998706650697
]

Using variables

Reference variables by their name. In this example the values a and b from the vars section. Only numerically-typed variables are available for use. Non-numeric variables can't be referenced.

{
    "topic": "sandbox",
    "vars": {
        "a": {
            "_gen": "uniformDistribution",
            "bounds": [
                5,
                10
            ]
        },
        "b": {
            "_gen": "uniformDistribution",
            "bounds": [
                2,
                3
            ]
        }
    },
    "value": {
        "_gen": "math",
        "expr": "a / b"
    }
}

[
    2.081172163164957,
    3.8940986599363123,
    2.8142547265173614
]

Returning integers

By default, math will return floating point numbers. You can trim them down, even down to integers, using the decimals function modifier.

{
    "topic": "sandbox",
    "vars": {
        "a": {
            "_gen": "normalDistribution",
            "mean": 20,
            "sd": 3
        },
        "b": {
            "_gen": "uniformDistribution",
            "bounds": [
                5,
                6
            ]
        }
    },
    "value": {
        "_gen": "math",
        "expr": "a * b",
        "decimals": 0
    }
}

[
    113,
    114,
    109
]

---

Specification

JSON schema

{
    "type": "object",
    "properties": {
        "expr": {
            "type": "string"
        }
    },
    "required": [
        "expr"
    ]
}