Built-in helper functions for use in predicator expressions.

This module provides a collection of utility functions that can be called within predicator expressions using function call syntax. These functions operate on values from the evaluation context and return computed results.

Available Functions

String Functions

• len(string) - Returns the length of a string
• upper(string) - Converts string to uppercase
• lower(string) - Converts string to lowercase
• trim(string) - Removes leading and trailing whitespace
• starts_with(string, prefix) - Tests whether a string starts with a prefix
• ends_with(string, suffix) - Tests whether a string ends with a suffix
• substring(string, start[, len]) - Extracts a substring from a start index
• index_of(string, sub) - Finds the index of a substring, or -1

List Functions

• concat(list1, list2) - Concatenates two lists

Examples

iex> Predicator.evaluate("len('hello')", %{})
{:ok, 5}

iex> Predicator.evaluate("upper('world')", %{})
{:ok, "WORLD"}

iex> Predicator.evaluate("starts_with('hello world', 'hello')", %{})
{:ok, true}

iex> Predicator.evaluate("ends_with('hello world', 'world')", %{})
{:ok, true}

iex> Predicator.evaluate("substring('hello world', 6)", %{})
{:ok, "world"}

iex> Predicator.evaluate("substring('hello world', 0, 5)", %{})
{:ok, "hello"}

iex> Predicator.evaluate("index_of('hello world', 'world')", %{})
{:ok, 6}

iex> Predicator.evaluate("index_of('hello world', 'nope')", %{})
{:ok, -1}

iex> Predicator.evaluate("concat([1, 2], [3])", %{})
{:ok, [1, 2, 3]}