eMacros

The Extensible Macros Library for PHP

Author: Emmanuel Antico
Last Modification: 07/01/2015

##About

eMacros is a PHP library based on [lisphp] (https://github.com/lisphp/lisphp "") that features a customizable LISP dialect interpreter.

##Requirements

An updated version of PHP 5.4 is required tu run this library.

##Installation

eMacros installation is performed via Composer. Add the following file to your project folder and perform the usual installation which is [described here] (http://getcomposer.org/doc/00-intro.md # installation-nix "").

composer.json

{
    "require": {
        "emacros/emacros": "1.1.*"
    }
}

##Introduction

The following example shows the implementation of a simple program that calculates the sum of 2 numbers.

include 'vendor/autoload.php';

use eMacros\Program\Program;
use eMacros\Environment\DefaultEnvironment;

//create program instance
$program = new Program('(+ 3 7)');

//run program
$result = $program->execute(new DefaultEnvironment);

//show results
echo $result; //prints 10

This script begins by creating a new instance of a program which receives the code to be interpreted. For being able to run a program an environment instance is required. The execute method performs the execution of a program using the environment provided as an argument. The obtained value is then returned.

There are several types of programs, each one of these can generate different types of results based on its instructions. The class Program defines the simplest type of program. This class returns the result of the last executed instruction. The following program includes 2 instructions but only one value is returned.

$program = new Program('(+ 3 7)(- 6 3)');

Since Program always returns the last generated value, instead of 10 we would have obtained 3, that is, the result of subtracting 3 to 6.

include 'vendor/autoload.php';

use eMacros\Program\ListProgram;
use eMacros\Environment\DefaultEnvironment;

$program = new ListProgram('(+ 3 7)(- 6 (+ 1 2))');
$result = $program->execute(new DefaultEnvironment);

echo $result[0]; //prints 10
echo $result[1]; //prints 3

The TextProgram class returns the result of concatenating each evaluated expression in a program. This example generates a message by using the concatenation operator.

include 'vendor/autoload.php';

use eMacros\Program\TextProgram;
use eMacros\Environment\DefaultEnvironment;

$program = new TextProgram('(. "Hel" "lo" " ")(. "Wo" "rld")');
$result = $program->execute(new DefaultEnvironment);

echo $result; //prints "Hello World"

##The DefaultEnvironment class

The DefaultEnvironment class defines a default execution environment where applications can run. An environment defines the list of symbols and operations that the program will be able to interpret. This ranges from simple operations such as arithmetic (+, -, *, /) to more complex ones (if, or, @name, Array::reverse). Symbols and operations are added to an environment by importing packages. Current implementation of the DefaultEnvironment class looks like the following:

namespace eMacros\Environment;

use eMacros\Package\CorePackage;
use eMacros\Package\StringPackage;
use eMacros\Package\ArrayPackage;
use eMacros\Package\RegexPackage;
use eMacros\Package\DatePackage;

class DefaultEnvironment extends Environment {
	public function __construct() {
		$this->import(new StringPackage);
		$this->import(new ArrayPackage);
		$this->import(new RegexPackage);
		$this->import(new DatePackage);
		$this->import(new CorePackage);
	}
}

CorePackage, StringPackage, ArrayPackage, etc are classes that define a list of symbols and operations to be used within a program. By importing a package to an environment we enable the use of symbols and operations defined within that package.

The DefaultEnvironment class comes with a fair amount of functions, which makes it ideal for start experimenting on our own. The rest of the packages can be found in the eMacros\Package namespace.

##Running programs from files

Programs can also be loaded from files. Having the application code in another file turns useful for adding comments, which improves readability. This program is similar to the previous example, except that it also returns the version of PHP running on the system.

; hello_world.em
; This is a comment
(. "Hello" " World!" "\n") ; Another comment
(. "This script is running under PHP " PHP_VERSION "\n") 
; END

This example uses the file_get_contents function to obtain the contents of a source file.

include 'vendor/autoload.php';

use eMacros\Program\TextProgram;
use eMacros\Environment\DefaultEnvironment;

$program = new TextProgram(file_get_contents('hello_world.em'));
$result = $program->execute(new DefaultEnvironment);

echo $result;

##The CorePackage class

The CorePackage class is extremely important when building a program execution environment. Among the elements that are contained on this package are:

• The null, true and false symbols.
• Arithmetic, comparison and logic operators.
• Variables and symbols functions.
• Class/objects functions.
• Argument functions.
• Type handling functions.
• Etc.

As noted, the functionality of this package is very critical so it is recommended to have it included whenever we create a customized environment. Below is a brief overview of the capabilities of this package.

#####Comparison operators

; comparison.em
; Comparison operators always return a boolean value

; equal
(== 1 "1") ; equal to
(!= 1 2) ; not equal to

; identical
(=== 1 1) ; identical to
(!== 1 "1") ; not identical to

; greater than
(> 6 4) ; greater than
(>= 4 4) ; greater than or equal to

; lesser than
(< 3 4) ; lesser than
(<= 3 3) ; lesser than or equal to

#####Logic operators

; logical.em

; AND OR
(and true true) ; true
(or false true) ; true

; several parameters
(and true true false true) ; false

; NOT
(not true) ; false

; IF
; if [CONDITION] [VALUE_TRUE]
; if [CONDITION] [VALUE_TRUE] [VALUE_FALSE]
(if true "is true") ; returns "is true"
(if false "is true" "is false") ; returns "is false"
(if false "is true") ; returns NULL

; COND
; cond searchs for the first non-false value on a list and returns the associated value
(cond (false 1)) ; returns NULL
(cond (false 1) (true 2) (false 3) (true 4)) ; returns 2

#####Arithmetic operators

; arithmetic.em

; add and substract
(+ (- 10 6) 6  1) ; 11

; multiplication and division
(* 4 (/ 10 5)) ; 8

; modulus
(mod 10 3) ; 1

#####Binary operators

; binary.em

; OR
; 1010 | 0110
(| 10 6) ; 14

; AND
; 0101 & 1110
(& 5 14) ; 4

#####Type functions

; types.em

; get type
(type-of 4) ; "integer"

; check type
(int? 4) ; true

; check types
(string? "" "hola" "mundo") ; true
(int? 5 3 "x") ; false

; empty
(empty? "") ; true
(empty? 1) ; false
(empty? false 0) ; true

#####Casting

; casting.em

; as-TYPE
(as-int "123") ; 123
(as-float "345.25") ; 345.25

; strval
(strval true) ; "1"

; intval
(intval 34.55) ; 34

; floatval
(floatval "13.45") ; 13.45

; boolval (solo PHP 5.5)
(boolval 0) ; false

#####Constants

• PHP_VERSION (same as PHP_VERSION)
• PHP_MAJOR_VERSION (same as PHP_MAJOR_VERSION)
• PHP_MINOR_VERSION (same as PHP_MINOR_VERSION)
• PHP_RELEASE_VERSION (same as PHP_RELEASE_VERSION)
• PHP_EXTRA_VERSION (same as PHP_EXTRA_VERSION)
• PHP_VERSION_ID (same as PHP_VERSION_ID)
• PHP_OS (same as PHP_OS)
• PHP_SAPI (same as PHP_SAPI)
• PHP_INT_MAX (same as PHP_INT_MAX)
• PHP_INT_SIZE (same as PHP_INT_SIZE)

##Variables

; variables.em

(:= _null null) ; _null = null
(:= _false false) ; _false = false
(:= _true true) ; _true = true

; numbers
(:= _two 2) ; declares _two = 2
(:= _five (+ 2 3)) ; declares _five = 2 + 3
(+ _two _five) ; 7

; strings
(:= _name "john")
(:= _message (. "Hello " _name)) ; build _message
(<- _message) ; returns _message value

; unset
(unset _name)
(<- _name) ; NULL

Alternatively, we can use the symbol manipulation functions: sym, sym-exists and lookup.

; symbols.em
; the sym functions receives a string and an associated values
(sym "_program" "variables.em") ; adds _program to the symbol table with the value "symbols.em"
(. "Running program " _program)

; sym-exists verifies if the given symbol exists on the symbol table
(if (sym-exists "_program") "Symbol \"_program\" already exists")

; lookup obtains a symbol associated value
(. "Ending execution of " (lookup "_program"))

##Arrays and objects

; arrays.em
; create an int array
(:= _list (array 1 2 3 4 5))
(. "_list has " (count _list) " elements")

; key-value pairs
(:= _data (array ("name" "john") ("surname" "doe") ("job" "developer")))

Objects can be created through 2 functions: new and instance. While new expects the class name defined as a symbol, instance creates an object instance from a string.

; objects.em
; create new stdClass instance
(:= _obj (new stdClass))

; create ArrayObject instance with a constructor parameter
(:= _arr (instance "ArrayObject" (array "one" "two" "three")))

; create DOMDocument instance
(:= _xml (new DOMDocument "1.0" "ISO-8859-1"))

In order to work with properties, CorePackage provides 3 operators.

; properties.em
; declare new instance
(:= _os (new stdClass))

; set key/property value (#=)
(#= "name" _os "GNU/Linux") ; _os->name = "GNU/Linux"
(#= "family" _os "Unix-like") ; _os->family = "Unix-like"

; get key/property value (#)
(. "System " (# "name" _os) " is a " (# "family" _os) " OS")

; check if key/property exists (#?)
(if (not (#? "company" _os)) " and is libre")

Same functions can be used with array keys.

; keys.em
(:= _arr (array ("program" "keys.em") ("language" "eMacros")))
(. "Program" (# "program" _arr) " is written in " (# "language" _arr))

; stores status in array
(#= "status" _arr "Running")

; check key existence
(if (#? "status" _arr) (. "Program status: " (# "status" _arr)) "Unknown status")

The CorePackage class also defines an abbreviated way for obtaining key/properties through macros.

; short_keys.em

;; OBJECTS

; create instance
(:= _os (new stdClass))

; assign value (#PROPERTY=)
(#name= _os "GNU/Linux") ; _os->name = "GNU/Linux"
(#family= _os "Unix-like") ; _os->family = "Unix-like"

; get value (#PROPERTY)
(. "System " (#name _os) " is a " (#family _os) " OS")

; check property (#PROPERTY?)
(if (not (#company? _os)) " and is libre")

;; ARRAYS
(:= _arr (array ("program" "keys.em") ("language" "eMacros")))
(. "Program " (#program _arr) " is written in " (#language _arr))

; stores program status
(@status= _arr "Running")

; check key existence
(if (#status? _arr) (. "Program status: " (#status _arr)) "Unknown status")

This operator supports numeric indexes as well.

; numeric_keys.em
(:= _arr (array))
(#0= _arr "First element")
(#-2= _arr "Index -2")

(if (not (#1? _arr)) "No element available on index 1")

(. "Array first element " (#0 _arr))

#####Class/Object functions

; class_functions.em
(:= _song (new stdClass))
(#name= _song "Meditango")
(#artist= _song "Astor Piazzolla")
(#genre= _song "Tango")

; get-object-vars
(get-object-vars _song) ; ["name" => "Meditango", "artist" => "Astor Piazzolla", "genre" => "Tango"]

; get-class
(get-class _song) ; "stdClass"

; instance-of
(instance-of _obj stdClass) ; true
(instance-of _obj ArrayObject) ; false

; is-a
(is-a _obj "stdClass") ; true
(is-a _obj "ArrayObject") ; false

; property-exists
(property-exists "eMacros\\Symbol" "package") ; true

; method-exists
(method-exists "ArrayObject" "count") ; true

; is-subclass-of
(is-subclass-of "eMacros\\Environment\\DefaultEnvironment" "eMacros\\Scope") ; true

; get-parent-class
(get-parent-class "eMacros\\Environment\\DefaultEnvironment") ; "eMacros\Environment\Environment"

; get-class-vars
(get-class-vars "eMacros\\Literal") ; ["value" => NULL]

; get-class-methods
(get-class-methods "eMacros\\Expression") ; ["evaluate"]

; class-alias
(class-alias "eMacros\\Symbol" "symbol")
(:= _song (new symbol "song"))

#####Method invocation

; methods.em
(:= _name (new ArrayObject (array "john" "charles" "peter")))
(-> "count" _names) ; 3

; abbreviated
(->count _nombres)

; parameters
; (now) obtains a DateTime instance with the current time
(->format (now) "Y-m-d H:i") ; get current date

##Arguments

A program can accept an arbitrary number of arguments. These must be specified right after the environment instance.

; arguments.em
; This program obtains the number of passed arguments

; argument counter (%#)
(. (%#) " parameters have been found\n")

; obtain arguments as array (%_)
(. "Arguments: " (implode "," (%_)))

This script performs the execution of the previous program with 3 arguments.

include 'vendor/autoload.php';

use eMacros\Program\TextProgram;
use eMacros\Environment\DefaultEnvironment;

//create program instance
$program = new TextProgram(file_get_contents('arguments.em'));

//add arguments
$result = $program->execute(new DefaultEnvironment, 1, "hello", 5.5);

//print results
echo $result;

The obtained output is the following:

3 parameters have been found
Parameters: 1,hello,5.5

We can access each argument individually with the corresponding functions:

; arg_functions.em

; get argument by index (%)
(+ 5 (% 0)) ; 5 + 1

; check argument existence (%?)
(if (%? 1) (. (% 1) " mundo")) ; "hola mundo"

; abbreviated form (%ARGN) (%ARGN?)
(if (%1?) (. (%1) " world")) ; "hello mundo"

#####The executeWith method

include 'vendor/autoload.php';

use eMacros\Program\TextProgram;
use eMacros\Environment\DefaultEnvironment;

//create program instance
$program = new TextProgram(file_get_contents('arguments.em'));

//run program
$result = $program->executeWith(new DefaultEnvironment, [1, "hello", 5.5]);

//print results
echo $result;

##Packages

eMacros has several packages available organized by type within the eMacros\Package namespace. The following script demonstrates the use of some functions that are available in the 'String' package.

; string_functions.em
; len (strlen)
(len "hello") ; 5

; explode
(explode "." "198.123.12.45") ; ["198", "123", "12", "45"]

; reverse (strrev)
(reverse "Hello") ; "olleH"

; str (strstr)
(str "email@example.com" "@") ; "@example.com"

Sometimes two packages define the same symbol, so that the use of a function or value becomes ambiguous. This is the case of shuffle and reverse, both declared in StringPackage and ArrayPackage. This problem can be solved using the package name as a symbol prefix.

; ambiguos.em

; reverse
(reverse "abcde") ; "edcba"
(Array::reverse (array "one" "two" "three")) ; ["three" "two" "one"]
(String::reverse "xyz") ; "zyx"

; aux array
(:= _arr (array 1 2 3))

; shuffle
(shuffle "abcde") ; shuffle in String package
(Array::shuffle _arr) ; shuffle in Array package
(String::shuffle "xyz") ; shuffle in String package

##Function invocation

The call and apply functions allow to invoke a function passed as argument.

; call_func.em
; shows some examples of call
(call "strtoupper" "hello world") ; returns "HELLO WORLD"

(call Array::range 2 5) ; returns [2, 3, 4, 5]

The apply function expects an array containing the list of arguments as a second parameter. This code uses apply to sum all arguments ​​passed to a program.

; sigma.em
; calculates the sum of all arguments passed
(apply + (%_))

##Use and Import

; use_example.em
; usage examples of use function

; import utf8_encode
(use utf8_encode)
(:= _encoded (utf8_encode (%0)))

; using an alias
(use (utf8_decode utf8dec))
(:= _decoded (utf8dec _encoded))

; multiple use
(use mb_detect_encoding mb_internal_encoding (mb_get_info mbinfo))

The import function expects a symbol with the package class name to import.

; import_example.em
; usage examples of import

; import MathPackage class
(import eMacros\Package\MathPackage)
(:= _sin (sin Math::PI_2))

; if no class is found then import tries to recover the package from the eMacros\Package namespace (and adding "Package" as suffix)
(import CType)
(if (digit (%0)) "Argument is a digit" "Argument is not a digit")

##User packages

The preferable way to implement user functions is through packages. By keeping our customized functions within packages we can import them into any environment more efficiently. The following example shows the implementation of a sample package that adds the symbols MY_CONSTANT and message to the environment's symbol table.

namespace Acme;

use eMacros\Package\Package;

class CustomPackage extends Package {
    public function __construct() {
        //declare and ID for this package
        parent::__construct('Custom');
        
        $this['MY_CONSTANT'] = 42;
        $this['message'] = "this is a custom package";
    }
}

While it is possible to import the symbols of this package through import, it turns more convenient to use a customized environment. The following example shows the implementation of a runtime environment defined by the user.

namespace Acme;

use eMacros\Environment\Environment;
use eMacros\Package\CorePackage;
use eMacros\Package\StringPackage;

class CustomEnvironment extends Environment {
    public function __construct() {
        $this->import(new CustomPackage);        
        $this->import(new StringPackage);
        $this->import(new CorePackage);
    }
}

Having already prepared our new user-defined environment we can make the implementation of programs using the previously declared symbols.

; custom.em
; An example using a user-defined environment
(<- MY_CONSTANT); returns 42

; using package name as prefix
(/ Custom::MY_CONSTANT 2) ; returns 21

(String::ucfirst message) ; returns "This is a custom package"

##Implementing user-defined functions

Creating macros and functions is done through 3 available classes and an auxiliary interface:

• PHPFunction (only functions available in PHP)
• Closures
• GenericFunction
• Applicable

#####PHPFunction

The PHPFunction class acts as a wrapper for PHP functions. This class constructor expects the name of the function to encapsulate.

namespace Acme;

use eMacros\Package\Package;
use eMacros\Runtime\PHPFunction;

class UserPackage extends Package {
    public function __construct() {
        parent::__construct('User');
        
        /**
         * Compress data
         * Usage: (compress "sample data")
         */
        $this['compress'] = new PHPFunction('bzcompress');
    }
}

By using PHPFunction we omit checking the amount parameters and their types. Still, it is the simplest way to import language features to a package.

; phpfunction.em
; compress a string
(compress "some string")

#####Closures

Functions defined as Closures can help to avoid implementing an entire class from scratch.

namespace Acme;

use eMacros\Package\Package;

class UserPackage extends Package {
    public function __construct() {
        parent::__construct('User');
        
        /**
         * Addition and sustraction
         * Usage: (plusmin 6 7 3) ; 10
         */
        $this['plusmin'] = function ($x, $y, $z) {
            return $x + $y - $z;
        });
    }
}

; closure.em
(+- 4 7 2) ; return 9

#####GenericFunction

Classes that extend from GenericFunction must implement the execute method. This method receives an array with all submitted arguments.

namespace Acme\Runtime;

use eMacros\Runtime\GenericFunction;

class PlusMin extends GenericFunction {
    /**
     * Addition and subtraction
     * Usage: (+- 4 5 1) ; 8
     */
    public function execute(array $args) {
        if (count($args) < 3) {
             throw new \BadFunctionCallException("PlusMin: At least 3 arguments are  required.");
        }
        
        return $args[0] + $args[1] - $args[2];
    }
}

This package adds a new symbol and assigns it to a new PlusMin instance.

namespace Acme;

use eMacros\Package\Package;
use Acme\Runtime\PlusMin;

class UserPackage extends Package {
    public function __construct() {
        parent::__construct('User');
        
        /**
         * Suma y resta
         * Uso: (+- 6 7 3) ; 10
         */
        $this['+-'] = new PlusMin;
    }
}

#####The Applicable interface

We can also create functions through the Applicable interface. This interface is useful if you need to access values declared within the runtime environment (constants, functions, parameters, etc.) or if you need to determine if a given parameter is defined as a symbol or literal. The apply method takes 2 arguments: an instance of Scope with the current execution environment and an instance of GenericList with the given arguments. To obtain an expression value we need to invoke its evaluate method using the Scope instance as argument. This example implements a class named Increment that increases the value of a symbol by one or by a given value (when specified).

namespace Acme\Runtime;

use eMacros\Scope;
use eMacros\GenericList;
use eMacros\Applicable;
use eMacros\Symbol;

class Increment implements Applicable {
    public function apply(Scope $scope, GenericList $arguments) {
        //check arguments amount
        $nargs = count($arguments);
        
        if ($nargs == 0) {
            throw new \BadFunctionCallException("Increment: No parameters found.");
        }
        
        //check that first parameter is a symbol
        if (!($arguments[0] instanceof Symbol)) {
            throw new \InvalidArgumentException("Increment: A symbol is expected as first argument.");
        }
        
        //get symbol name
        $ref = $arguments[0]->symbol;
        
        //get symbol value
        $value = $arguments[0]->evaluate($scope);
        
        if ($nargs > 1) {
            $value += intval($arguments[1]->evaluate($scope));
        }
        else {
            $value++;
        }
        
        $scope->symbols[$ref] = $value;
        return true;
    }
}

Notice that this class ensures that the first parameter is a symbol or otherwise an exception is thrown.

namespace Acme;

use eMacros\Package\Package;
use Acme\Runtime\Increment

class UserPackage extends Package {
    public function __construct() {
        parent::__construct('User');
        
        /**
         * Increments a variable value
         * Usaeg: (inc _x) (inc _y 3)
         */
        $this['inc'] = new Increment();
    }
}

The following code imports the UserPackage class and shows an usage example of the inc function.

; inc.em
; Example using the inc function
(import Acme\UserPackage)
(:= _x 1)
(inc _x) ; _x = 2
(inc _x 3) ; _x = 5

##Macros

Macros are functions that instead of being associated with a symbol they're generated from a regular expression. Macros are declared using the macro method. This method expects a regular expression string and a Closure instance (or anonymous function). This anonymous function receives all matches found for the given regular expression. Its main purpose is to generate a valid environment function with those matches. The following example shows the implementation of a macro to calculate the distance between 2 points. The coordinates of the starting point are declared as part of the operator and then captured by the anonymous function.

namespace Acme\Runtime;

use eMacros\Runtime\GenericFunction;

class Distance extends GenericFunction {
    public $x;
    public $y;

    public function __construct($coordX, $coordY) {
        $this->x = $coordX;
        $this->y = $coordY;
    }
    
    /**
     * Calculates the distance between 2 point
     * Usage: (dist:X1Y7 3 5)
     */
    public function execute(array $args) {
        if (count($args) < 2) {
            throw new \BadFunctionCallException("Distance: Destination not specified.");
        }
        
        $x = intval($args[0]);
        $y = intval($args[1]);
        
        $distance = pow($x - $this->x, 2) + pow($y - $this->y, 2);
        return sqrt($distance);
    }
}

The dist macro can be invoked directly without the need of specifying coordinates of origin. In that case, the distance will be calculated from the coordinates (0,0). The following code shows the implementation of the GeometryPackage class. This class adds dist to the symbol table and defines the customizable macro for calculating distances.

namespace Acme;

use eMacros\Package\Package;
use Acme\Runtime\Distance;

class GeometryPackage extends Package {
    public function __construct() {
        parent::__construct('Geometry');
        
        //default distance
        $this['dist'] = new Distance(0, 0);

        //macro style
        $this->macro('@dist:X(\d+)Y(\d+)@', function ($matches) {
            return new Distance(intval($matches[1]), intval($matches[2]));
        });
    }
}

The next example invokes the *dist" macro using both modes (with and without coordinates).

; distance.em
; User-defined macro example
(import Acme\GeometryPackage)

; distance from (0,0)
(dist 4 2)

; distance from (4, 2)
(dist:X4Y2 5 7)

##Appendix I - Available packages

##License

This code is licensed under the BSD 2-Clause license.