Skip to main content

OnPing Script Language

Daniel Casanueva
Updated

Literals

Literals are values that you write directly in the script, like 0.8 or 120.
There are three kinds of literals:

  • Numeric literal (with decimals): 0.80, 100.0, etc. They have type Double.
  • Numeric literal (without decimals): 120, 1234, etc. They have type Int.
  • Hexadecimal literal: 0xA9F, 0x8D01, etc. They have type Word64.
  • Unit literal: ().

Variables

Variables are names that represent values, like foo or bar. They always start by
a letter, and are followed by zero or more letters or numbers. Examples of valid
variables are: x, y, MyVariable, ThisIsAVariable, this2isavariable, Year2018.

Types

Types are the kinds of values a script can work with. For instance, there are numbers,
times, or booleans. Types are used to clasify values and to provide useful information
when a script contains a mistake (like adding a boolean to an integer, or passing the
wrong parameter to a function). A list of all types available in scripts follow:

  • Int: Integer numbers. These are numbers without decimals.
  • Double: Double-precision floating numbers. These are numbers with decimals.
  • Bool: Truth values. This type has only two members: true and false.
  • Unit: A type with a single value: ().
  • EpochTime: Points in time. For how to build values of this type, see the “Time functions”
    section.
  • Word16: Unsigned 16-bit integeres.
  • Word32: Unsigned 32-bit integeres.
  • Word64: Unsigned 64-bit integeres.
  • * -> * (function type): A value can also be a function. For instance, a function
    that takes a Double and returns an Int has type Double -> Int.

Functions

Like we mentioned earlier (see the Types section), a variable can contain a function. To
apply an argument to a function, simply put in parenthesis the argument right after the
function variable. For example, if we have a function called f of type Double -> Bool,
and a variable x of type Double, the function f can be applied to x simply by
typing f(x). The result will have type Bool.

The input function

Warning: this function is only available when using virtual parameters.

There is a special predefined function called input. It is used to get values from the
parameters associated to a virtual parameter. Its type is Int -> EpochTime -> Double.
The first parameter is the parameter index. If you assigned two parameters to the virtual
parameter, the first parameter has index 1, and the second parameter has index 2.
The second argument of input is the time to get the value from. For example, input(1,now)
will get the current value of the first parameter. If there is no value at the given time,
() will be returned.

The alias input1 is also available, and it’s equivalent to input(1,now). This alias can
be used when migrating scripts from masks to virtual parameters.

The latestBefore function

Warning: this function is only available when using virtual parameters.

This function gets the latest value from a parameter before a given time. An example:

x := latestBefore(now - days(3), 1);

In this example, x is set to the latest value of the parameter 1 before three days ago.

The latestInput function

Warning: this function is only available when using virtual parameters.

This function works similarly to input, but only has the parameter index argument.
The time time will be automatically set to the time of the latest value in the
parameter.

Note: It is equivalent to latestBefore(now).

Assignments

To assign a value to a variable, the following syntax is used:

<variable> := <expression> ;

Where <variable> is any variable name, and <expression> is any expression involving
variables and literals. An example:

x := 2 + sqrt(3) ;

After this statement, the value of x will be the result of evaluating the expression 2 + sqrt(3).
Please note the semicolon after the expression in the assignment syntax.

Clearing a variable

To clear the value of a variable, use the following syntax:

<variable> ;

After this statement, the variable will be left undefined.

Conditionals

Using conditionals you can choose to execute one of two options. The syntax goes as
follows:

IF <boolean expression>
  THEN
    <code 1>
  ELSE
    <code 2>
END_IF ;

The ELSE part is optional. This works too:

IF <boolean expression>
  THEN
    <code>
END_IF ;

This way, the code inside the conditional will only be executed if the boolean expression evaluates
to true.

Time loops

Time loops are a handy tool to execute some code for a sequence of time values. This is the syntax:

WITH <variable> FROM <time expression> TO <time expression> EVERY <time expression> DO
  <code>
END_LOOP ;

This code will do as follows:

  1. Set the value of the variable to the value of the FROM time. Therefore, the variable will
    hold a value of type EpochTime.
  2. Run the code.
  3. Increase the value of the variable by the value of the EVERY time.
  4. Run the code.
  5. Repeat this procedure until the value of the variable reaches the value of the TO time.

An example:

acc := 0;
WITH t FROM now - days(5) TO now EVERY minutes(30) DO
  x := input(1,t);
  IF not(isUnit(x))
    THEN acc := acc + x;
  END_IF;
END_LOOP ;

This time loop will add all values from the input parameter 1 from the last 5 days, every
30 minutes. The result will be stored in the acc variable. Sometimes there is no value
at time t, so we need to use isUnit to account for this case.

Predefined functions and operators

Arithmetic

Addition (+) and substraction (-) can be used with Int, Double, and EpochTime.
Multiplication and division only with Int and Double. Division always gives a result
of type Double, to account for potential inexact divisions.
Exponentiation is done with **. For example, 2 ** 3 = 8.

Boolean values

The boolean values are True and False. Lower-cased variants (true and false) are also defined.
The function not :: Bool -> Bool gives True for False, and False for True.

Logical operators

  • || :: Bool -> Bool -> Bool: Logical disjunction. OR is also accepted.
  • && :: Bool -> Bool -> Bool: Logical conjunction. AND is also accepted.
  • XOR :: Bool -> Bool -> Bool: Exclusive disjunction.
  • isSet :: Int -> Int -> Bool: Check if the bit indicated by the second argument is set.
    For any n: 0 isSet n = False.

Integer operators

  • MOD :: Int -> Int -> Int: Modulo operation. Example: 9 MOD 4 = 1.

Truncation operator

The operator ` :: Double -> Int -> Double truncates a number to the given number of decimals. TRUNC is also accepted.

Rounding functions

All rounding functions return integers. They accept both Double and Int arguments, but they
leave Int values unmodified. The rounding functions are:

  • floor: Round to the closest smaller (or equal) integer.
  • ceiling: Round to the closest bigger (or equal) integer.
  • round: Round to the closest integer.
  • truncate: Round by removing the decimal part.

Comparison operators

All operators work with Int and Double, and only values of the same type can be compared.
The available operators are:

  • ==: Equality. The use of equality with Double is not recommended.
  • <>: Inequality.
  • <: Less than.
  • <=: Less or equal to.
  • >: Greater than.
  • >=: Greater or equal to.

Comparison functions

The functions max and min have two arguments can be used with values of Int, Double, and EpochTime.
They return the smallest (or largest) of its arguments. For example: max(-2,1) = 1, min(-3,2) = -3.

Sign functions

The functions abs and negate can be applied to values of type Int or Double. The function
abs returns the absolute value of a number, and the function negate calculates the opposite
number.

Time functions

  • now :: EpochTime: A constant value with the current time. Its value does not change during the
    execution of the script.

  • seconds :: Int -> EpochTime: A number of seconds.

  • minutes :: Int -> EpochTime: Minutes.

  • hours :: Int -> EpochTime: Hours.

  • weeks: Int -> EpochTime: Weeks.

  • monthsAgo :: Int -> EpochTime: The time a given number of months ago.

  • hour :: EpochTime -> EpochTime: Returns time at the start of the hour.

  • day :: EpochTime -> EpochTime: Returns time at the start of the day (midnight).

  • month :: EpochTime -> EpochTime: Returns time at the start of the month.

  • year :: EpochTime -> EpochTime: Returns time at the start of the year.

Casting functions

  • double :: Int -> Double: Cast an Int value to a Double value.
  • boolToInt :: Bool -> Int: Cast a Bool value to an Int value. False becomes 0, and True becomes 1.
  • intToBool :: Int -> Bool: Cast an Int value to a Bool value. 0 becomes False, and anything else True.
  • timeToInt :: EpochTime -> Int: Cast an EpochTime value to an Int value. The result is the number of
    seconds since January 1, 1970, 00:00, not counting leap seconds. You can use seconds to get the
    EpochTime back.
  • doubleBits :: Double -> Word64: Cast a Double value to an unsigned integer that has the same bits set.

Floating point number functions

  • recip :: Double -> Double: Calculate the inverse of a number. For example: recip(2) = 0.5.
  • sqrt :: Double -> Double: Calculate the square root of a number.
  • limit :: Double -> Double -> Double -> Double. The expression limit(l,u,x) will evaluate to:
    • l if x <= l.
    • u if x >= u.
    • x otherwise.

Unsigned integer functions

These functions work with Word16, Word32 and Word64 types. We would refer to them as WordN in the following
functions.

  • testBit :: WordN -> Int -> Bool: Test if the nth bit is 1.
  • setBit :: WordN -> Int -> WordN: Set the nth bit to 1.
  • clearBit :: WordN -> Int -> WordN: Set the nth bit to 0.
  • complementBit :: WordN -> Int -> WordN: Set the nth bit to 0 if it’s 1, or to 1 otherwise.
  • complement :: WordN -> WordN: Complement every bit. Example: complement(0xF0) = 0x0F.
  • shift :: WordN -> Int -> WordN: Shift the given number of bits. The number can be negative for
    a negative shift. Examples: shift(0x0F0,4) = 0xF00, shift(0x0F0,-4) = 0x00F, shift(0x0F0,-8) = 0x0.
  • fromWord :: WordN -> Int: Transform to signed integer. Overflow possible if argument is outside of the
    signed integer type range.

Unsigned integer operators

  • .&.: bit-wise and.
  • .|.: bit-wise or.
  • XOR: bit-wise xor.

Transforming between different unsigned integer types

Three functions are available: toWord16, toWord32 and toWord64. They all work for all unsigned integer types.
If the target type is smaller than the argument type, any excess bits will be truncated. The function toWord64 can
also be used to produce a Word64 from an Int, which will have the same bit representation as the original Int but
might have a different value.

Random numbers

  • random :: () -> Double: Get a random number in the [0,1) interval. Example where x is assigned a random number between 0 and 10: x := 10 * random() ;.
    The () argument is needed to make possible that each time random is called a new random value can be generated.

Unit check

The function isUnit :: * -> Bool accepts arguments of any type, and returns True when the
argument is ().

Trigonometrics

  • pi :: Double. The Pi constant.
  • sin :: Double -> Double. Sine.
  • cos :: Double -> Double. Cosine.
  • tan :: Double -> Double. Tangent.

Comments

0 comments

Please sign in to leave a comment.

Powered by Zendesk