OnPing Script Language

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 fof 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.
• fromDoubleBits :: Word64 -> Double.
  The inverse function of doubleBits.

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.