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Function expressions¤

Overview¤

!ARGUMENT, !ARG¤

Provides an access to an argument name.

Type: Scalar.

Synopsis:

!ARGUMENT name

or

!ARG name

Tip

!ARG is an concise version of !ARGUMENT.

!FUNCTION, !FN¤

The !FUNCTION expression defines a new function. It is typically used as a top-level expression.

Type: Mapping.

Info

SP-Lang expressions are implicitly_placed function definition. It means that in a majority of cases, the expression !FUNCTION can be skipped, and only do section is provided.

Synopsis:

!FUNCTION
name: <name of function>
arguments:
  arg1: <type>
  arg2: <type>
  ...
returns: <type>
schemas: <dictionary of schemas>
do:
  <expression>

Tip

!FN is an concise version of !FUNCTION.

Example

!FUNCTION
arguments:
  a: si64
  b: si32
  c: si32
  d: si32
returns: fp64
do:
  !MUL
  - !ARGUMENT a
  - !ARGUMENT b
  - !ARGUMENT c
  - !ARGUMENT d

This expression defines a function that takes four arguments (a, b, c, and d) with respective data types (si64, si32, si32, and si32) and returns a result of type fp64. The function multiplies the four input arguments (a, b, c, and d) and returns the product as a floating-point number (fp64).

!SELF¤

The !SELF provides an ability to recursively apply "self" aka a current function.

Type: Mapping.

Synopsis:

!SELF
arg1: <value>
arg2: <value>
...

Note

!SELF expression is the so called Y combinator.

Example

!FUNCTION
arguments: {x: int}
returns: int
do:
  !IF # value <= 1
    test: !GT [!ARG x, 1]
    then: !MUL [!SELF {x: !SUB [!ARG x, 1]}, !ARG x]
   else: 1

This expression defines a recursive function that takes a single integer argument x and returns an integer result. The function calculates the factorial of the input argument x using an if-else statement. If the input value x is greater than 1, the function multiplies x by the factorial of (x - 1), computed by calling itself recursively. If the input value x is 1 or less, the function returns 1.