I've been writing Java for the last couple of years , and now I've started to write in python (in addition).
The problem is that when I look at my Python code it looks like someone tried to hammer Java code into a python format , and it comes out crappy because - well , python ain't Java.
Any tips on how to escape this pattern of "Writing Java in Python"?
Thanks!
You might consider immersing yourself in the Python paradigms. The best way is to first know what they are then explore the best practices by reading some literature and reviewing some code samples. I recommend Learning Python by Mark Lutz; great for beginners and advanced users.
You'll do yourself a great injustice if you program with Python and fail to leverage all of the built-in, developer-friendly, Pythonic syntax.
As my French teacher used to say, "French isn't just English with different words."
If you are new to Python and coming from Java (or C#, or other similar statically typed OO language), these classic articles from PJ Eby and Ryan Tomayko are necessary reading:
Python Is Not Java (PJE)
Java is not Python, either (PJE)
Python Interfaces are not Java Interfaces (PJE)
The Static Method Thing (Tomayko)
Getters/Setters/Fuxors (Tomayko)
You could start by reading The Zen of Python. It'll give you some insight into how Python code is supposed to be written, provided you understand the language enough to understand what it's talking about. :-)
Some of the major ways in which Python differs from C/Java-like languages are:
List comprehensions.
Support for functional programming.
The use of certain Pythonic constructs instead of similar C-like constructs although both seem to work (list comprehensions can be argued to be a part of this, but there are others).
There are others, but these are the main ones that bugged me when I first started Python (and I had come from years of Java like you).
Before using any of these, it is helpful to understand why you should go for pythonic code rather than the usual C/Java way in Python, although both give you the same output.
For starters, Python provides some powerful features not available in C/Java that makes your code much clearer and simpler (although this is subjective, and might not look any better to someone coming from Java at first). The first two points fall into this category.
For example, support for functions as first class objects and closures makes it easy to do things that would need all kinds of weird acrobatics with inner classes in Java.
But a major reason is that Python is an interpreted language, and certain constructs are much faster than the equivalent C/Java-like code. For example, list comprehensions are usually a lot faster than an equivalent for-loop that iterates over the indices of a list and accesses each item by index. This is a very objective benefit, and IMHO a lot of the "Python in way too slow" way of thinking comes from using Java-style code shoe-horned into Python.
One of the best ways to learn about pythonic code is to read other people's code. I actually learnt a lot by looking at Python code posted in answers to SO questions. These often come with explanations and it is usually obvious why it is better than non-pythonic code (speed, clarity, etc.).
Edit:
Of course, there are other ways of getting other people's code. You can also download and look through the code of any good open source Python project. Books are also a good resource, I would recommend O'Reilly Python Cookbook. It has lots of useful code examples and very detailed explanations.
1) Python supports many (but not all) aspects of
object-oriented programming; but it is
possible to write a Python program without
making any use of OO concepts.
1) Java supports only object-oriented
programming.
2) Python is designed to be used interpretively.
A Python statement may be entered at the
interpreter prompt
(>>>)
, and will be executed
immediately. (Implementations make some
use of automatic compilation into bytecodes
(.pyc files).
2) Programs written in Java must be explicitly
compiled into bytecodes (.class files),
though an IDE may do this automatically in a
way that is transparent to the user. Java does
not support direct execution of statements -
though there are tools like Dr. Java that
support this.
3) Python is dynamically typed:
• A variable is introduced by assigning a
value to it. Example:
someVariable = 42
• A variable that has been assigned a value of
a given type may later be assigned a value
of a different type. Example:
someVariable = 42
someVariable = 'Hello, world'
3) Java is
statically typed
:
• A variable must be explicitly declared to be
of some type before assigning a value to it,
though declaration and assignment may be
done at the same time. Examples:
int someVariable;
int someVariable = 42;
• A variable that has been declared to be of a
particular type may not be assigned a value
of a different type.
4) Python supports the following built-in data
types:
Plain integers (normally 32-bit integers in
the range -2147483648 through
2147483647).
• Long integers (size limited only by memory
size of the machine running on)
• Booleans (False and True).
• Real numbers.
• Complex numbers.
In addition, Python supports a number of
types that represent a collection of values -
including strings, lists, and dictionaries.
4) Java has two kinds of data types: primitive
types and reference types. Java supports the
following primitive data types:
• byte - 8-bit integers
• short - 16-bit integers
• int - 32-bit integers
• long - 64-bit integers (Java also supports a
class java.math.BigInteger to represent
integers whose size is limited only by
memory)
• float - 32-bit real numbers.
• double - 32-bit real numbers.
• boolean - (false and true).
• char - a single character.
In addition, Java supports arrays of any type
as the reference types, and the API includes
the class String and a large number of classes
used for collections of values.
5)
Python is line-oriented:
statements end at the
end of a line unless the line break is explicitly
escaped with . There is no way to put more
than one statement on a single line.
Examples:
this is a statement
this is another statement
this is a long statement that extends over more \
than one line
5)
Statements in Java always end with a
semicolon (;)
. It is possible for a statement to
run over more than one line, or to have
multiple statements on a single line.
Examples:
this is a statement;
this is another statement;
this is a long statement that extends over more
than one line;
a statement; another; another;
6)
Python comments begin with #
and extend to
the end of the line. Example:
This is a comment
A new statement starts here
6) Java has two kinds of comments. A comment
beginning with // extend to the end of the
line (like Python comments). Comments can
also begin with /* and end with */. These
can extend over multiple lines or be
embedded within a single line. Examples:
// This is a comment
A new statement starts here
/* This is also a comment */
/* And this is also a comment, which is
long enough to require several lines
to say it. */
Statement starts /* comment */ then continues
7) Python strings can be enclosed in either single
or double quotes (' or ""). A character is
represented by a string of length 1. Examples:
'This is a string'
"This is also a string" # Equivalent
'c' # A string
"c" # An equivalent string
Python uses the following operators for
constructing compound boolean expressions:
and, or and not. Example:
not(x > 0 and y > 0) or z > 0
7) Java strings must be enclosed in double
quotes (""). A character is a different type of
object and is enclosed in single quotes (').
Examples:
"This is a String"
'c' // A character, but not a String
Java uses the following operators for
constructing compound boolean expressions:
&&, ||, ! and ^ (meaning exclusive or)
Example:
! (x > 0 && y > 0) || z > 0 ^ w > 0
8) In Python, the comparison operators
(>, <, >=, <=, == and !=) can be applied to numbers
,
strings, and other types of objects), and
compare values in some appropriate way (e.g.
numeric order, lexical order) where possible.
8) In Java, most of the comparison operators
( >, <, >=, and <=) can be applied only to
primitive types. Two (== and !=) can be
applied to any object, but when applied to
reference types they test for same (different)
object rather than same (different) value.
9) There is no universally-accepted Python
convention for naming classes, variables,
functions etc.
9) By convention, most names in Java use mixed
case. Class names begin with an uppercase
letter; variable and function names begin with
a lowercase letter. Class constants are named
using all uppercase letters with underscores.
Examples:
AClassName
aVariableName
aFunctionName()
A_CLASS_CONSTANT
10) Python definite looping statements have the
form for variable in expression: Example:
for p in pixels:
something
10) Java has two kinds of definite looping
statements. One has the form
for (variable in collection) Example:
for (p in pixels)
something;
11) Python uses the built-in function range() with
for to loop over a range of integers.
Examples:
for i in range(1, 10)
something
(i takes on values 1, 2, 3, 4, 5, 6, 7, 8, 9)
for i in range(1, 10, 2)
something
(i takes on values 1, 3, 5, 7, 9)
11) Java uses a different form of the for to loop
over a range of integers. Examples:
for (int i = 1; i < 10; i ++)
something;
(i takes on values 1, 2, 3, 4, 5, 6, 7, 8, 9)
for (int i = 1; i < 10; i += 2)
something;
(i takes on values 1, 3, 5, 7, 9)
12) Python conditional statements have the form
if condition: and an optional else part has the
form else:. The form elif condition: is
allowed as an alternative to an else:
immediately followed by an if. Examples:
if x < 0:
something
if x < 0:
something
else:
something different
if x < 0:
something
elif x > 0:
something different
else:
yet another thing
12) Java conditional statements have the form
if (condition) and an optional else part has
the form else (no colon) There is no elif
form - else if is used directly. Examples:
if (x < 0)
something;
if (x < 0)
something;
else
something different;
if (x < 0)
something;
else if (x > 0)
something different;
else
yet another thing;
13) The scope of a Python conditional or looping
statement is denoted by indentation. (If
multiple lines are to be included, care must be
used to be sure every line is indented
identically). Examples:
if x < 0:
do something
do another thing regardless of the value of x
if x < 0:
do something
do something else
do yet a third thing
do another thing regardless of the value of x
13) The scope of a Java conditional or looping
statement is normally just the next statement.
Indentation is ignored by the compiler
(though stylistically it is still highly desirable
for the benefit of a human reader). If
multiple lines are to be included, the scope
must be delimited by curly braces ({ , }).
(Optionally, these can be used even if the
scope is a single line.) Examples:
if (x < 0)
do something;
do another thing regardless of the value of x;
if (x < 0)
do something; // Bad style-don't do this!
do another thing regardless of the value of x;
if (x < 0)
{
do something;
do something else;
do yet a third thing;
}
do another thing regardless of the value of x;
if (x < 0)
{
do something;
}
do another thing regardless of the value of x;
If you want to see some fairly idiomatic Python that does non-trivial stuff, there's Dive Into Python, although Dive Into Python 3 is newer and might be a better source of style tips. If you're looking more for some points to review, there's Code Like a Pythonista.
You could post your code at Refactor my code to see if someone can show you a more Pythonic way to do it.
Definitely not a panacea but I think you should try some code golf in Python. Obviously nobody should write "golfed" code IRL, but finding the most terse way to express something really forces you to exploit the built in functionality of the language.
Someone provided me with this list of how "Python is not Java" when I started Python after Java, and it was very helpful.
Also, check out this similar SO question that I posted a short time ago when in a similar position.
Try to find algorithms that you understand well and see how they are implemented in python standard libraries.
Persist. :)
Learn a few other languages. It will help you make the difference between algorithms (the structure of processing, unchanged between languages) and the local syntaxic features of the language. Then you can "write Foo in Bar" for any combination of languages "Foo" and "Bar".
Eat Python, Sleep Python and Drink Python. That is the only way........
This is useful if you want to understand how to code to python in a more pythonic or correct way: http://www.python.org/dev/peps/pep-0008/
Related
I have a map in java Map<String,Object> dataMap whose content looks like this -
{country=Australia, animal=Elephant, age=18}
Now while parsing the map the use of various conditional statements may be made like-
if(dataMap.get("country").contains("stra")
OR
if(dataMap.get("animal") || 100 ==0)
OR
Some other operation inside if
I want to create a config file that contains all the rules on how the data inside the Map should look like. In simple words, I want to define the conditions that value corresponding to keys country, animal, and age should follow, what operations should be performed on them, all in the config file, so that the if elses and extra code can be removed. The config file will be used for parsing the map.
Can someone tell me how such a config file can be written, and how can it be used inside Java?
Sample examples and code references will be of help.
I am thinking of creating a json file for this purpose
Example -
Boolean b = true;
List<String> conditions = new ArrayList<>();
if(dataMap.get("animal").toString().contains("pha")){
conditions.add("condition1 satisifed");
if(((Integer.parseInt(dataMap.get("age").toString()) || 100) ==0)){
conditions.add("condition2 satisifed");
if(dataMap.get("country").equals("Australia")){
conditions.add("condition3 satisifed");
}
else{
b=false;
}
}
else{
b=false;
}
}
else{
b=false;
}
Now suppose I want to define the conditions in a config file for each map value like the operation ( equals, OR, contains) and the test values, instead of using if else's. Then the config file can be used for parsing the java map
Just to manage expectations: Doing this in JSON is a horrible, horrible idea.
To give you some idea of what you're trying to make:
Grammars like this are best visualized as a tree structure. The 'nodes' in this tree are:
'atomics' (100 is an atom, so is "animal", so is dataMap).
'operations' (+ is an operation, so is or / ||).
potentially, 'actions', though you can encode those as operations.
Java works like this, so do almost all programming languages, and so does a relatively simple 'mathematical expression engine', such as something that can evaluate e.g. the string "(1 + 2) * 3 + 5 * 10" into 59.
In java, dataMap.get("animal") || 100 ==0 is parsed into this tree:
OR operation
/ \
INVOKE get[1] equality
/ \ / \
dataMap "animal" INT(100) INT(0)
where [1] is stored as INVOKEVIRTUAL java.util.Map :: get(Object) with as 'receiver' an IDENT node, which is an atomic, with value dataMap, and an args list node which contains 1 element, the string literal atomic "animal", to be very precise.
Once you see this tree you see how the notion of precedence works - your engine will need to be capable of representing both (1 + 2) * 3 as well as 1 + (2 * 3), so doing this without trees is not really possible unless you delve into bizarre syntaxis, where the lexical ordering matching processing ordering (if you want that, look at how reverse polish notation calculators work, or something like fortran - stack based language design. I don't think you'll like what you find there).
You're already making language design decisions here. Apparently, you think the language should adopt a 'truthy'/'falsy' concept, where dataMap.get("animal") which presumably returns an animal object, is to be considered as 'true' (as you're using it in a boolean operation) if, presumably, it isn't null or whatnot.
So, you're designing an entire programming language here. Why handicap yourself by enforcing that it is written in, of all things, JSON, which is epically unsuitable for the job? Go whole hog and write an entire language. It'll take 2 to 3 years, of course. Doing it in json isn't going to knock off more than a week off of that total, and make something that is so incredibly annoying to write, nobody would ever do it, buying you nothing.
The language will also naturally trend towards turing completeness. Once a language is turing complete, it becomes mathematically impossible to answer such questions as: "Is this code ever going to actually finish running or will it loop forever?" (see 'halting problem'), you have no idea how much memory or CPU power it takes, and other issues that then result in security needs. These are solvable problems (sandboxing, for example), but it's all very complicated.
The JVM is, what, 2000 personyears worth of experience and effort?
If you got 2000 years to write all this, by all means. The point is: There is no 'simple' way here. It's a woefully incomplete thing that never feels like you can actually do what you'd want to do (which is express arbitrary ideas in a manner that feels natural enough, can be parsed by your system, and when you read back still makes sense), or it's as complex as any language would be.
Why not just ... use a language? Let folks write not JSON but write full blown java, or js, or python, or ruby, or lua, or anything else that already exists, is open source, seems well designed?
In Java, consider the following piece of code:
Vector v = new Vector();
for(int i = 1; i <= 10; i++)
{
v.addElement(Integer.toString(i));
}
System.out.println(v.elementAt(9).toString());
Are Java statements like v.elementAt(9).toString() containing multiple '.' operators perfectly fine enough at all or do they cause any given type of conflict during some given period of time after all?
So far, I have only always kept them as safe enough in parenthesis, by making use of putting away off parenthesis around individual statements, so as not to create with any given type of conflict at all, after all.
(v.elementAt(9)).toString().
So far, I have never created with any given type of ambiguous statements like that during all of my own more than over a decade of programming and coding experience.
v.elementAt(9).toString().
Are Java statements like v.elementAt(i).toString() containing multiple '.' perfectly fine enough at all or do they cause any given type of conflict during some given period of time after all?
They are perfectly fine, with some caveats. If v.elementAt(i) is null, then calling v.elementAt(i).toString() will throw a NullPointerException. If you select i as some value that is either negative or larger than the Vector, I suspect an ArrayIndexOutOfBoundsException will be thrown as well. You can think of this syntax as the composition of functions (left-to-right), which is opposite how it is in mathematics.
In your specific example, this syntax is logically equivalent:
(v.elementAt(i)).toString()
Why in java (I dont know any other programming languages) can an identifier not start with a number and why are the following declarations also not allowed?
int :b;
int -d;
int e#;
int .f;
int 7g;
Generally you put that kind of limitation in for two reasons:
It's a pain to parse electronically.
It's a pain for humans to parse.
Consider the following code snippet:
int d, -d;
d = 3;
-d = 2;
d = -d;
If -d is a legal identifier, then which value does d have at the end? -3 or 2? It's ambiguous.
Also consider:
int 2e10f, f;
2e10f = 20;
f = 2e10f;
What value does f have at the end? This is also ambiguous.
Also, it's a pain to read either way. If someone declares 2ex10, is that a typo for two million or a variable name?
Making sure that identifiers start with letters means that the only language items they can conflict with are reserved keywords.
That's because section 3.8 of the Java Language Specification says so.
An identifier is an unlimited-length
sequence of Java letters and Java
digits, the first of which must be a
Java letter. An identifier cannot have
the same spelling (Unicode character
sequence) as a keyword (§3.9), boolean
literal (§3.10.3), or the null literal
(§3.10.7).
As for why this decision was made: probably because this simplifies parsing, avoids ambiguous grammar, allows introduction of special syntax in a later version of the language and/or for historical reasons (i.e. because most other languages have the same restrictionsimilar restrictions). Note that your examples example with -d is especially clear:
int -d = 7;
System.out.println("Some number: " + (8 + -d));
Is the minus the first part of an identifier, or the unary minus?
Furthermore, if you had both -d and d as variables, it would be completely ambiguous:
int -d = 7;
int d = 2;
System.out.println("Some number: " + (8 + -d));
Is the result 15 or 6?
I don't know exactly but i think that's because numbers are used to represent literal values, so when the compiler find a token that starts with a number, it knows it is dealing with a literal. if an identifier could start with a number, the compiler would need to use a look ahead to find the next character in the token to find out if it is an identifier or a literal.
Such things aren't allowed in just about any language (I can't think of one right now), mostly to prevent confusion.
Your example -d is an excellent example. How does the compiler know if you meant "the variable named -d" or "the negative of the number in the variable d"? Since it can't tell (or worse yet, it could so you couldn't be sure what would happened when you typed that without reading the rest of the file), it's not allowed.
The example 7g is the same thing. You can specify numbers as certain bases or types by adding letters to the end. The number 8357 is an int in Java, where as 8357L is a long (since there is an 'L' on the end). If variables could start with numbers, there would be cases where you couldn't tell if it was supposed to be a variable name or just a literal.
I would assume the others you listed have similar reasons behind them, some of which may be historical (i.e. C couldn't do it for reason X, and Java is designed to look like C so they kept the rule).
In practice, they are almost never a problem. It's very rare you find a situation where such things are annoying. The one you'll run into the most is variables starting with numbers, but you can always just spell them out (i.e. oneThing, twoThing, threeThing, etc.).
Languages could allow some of these things, but this simplifying assumption makes it easier on the compiler writer, and on you, the programmer, to read the program.
Parsers are (usually) written to break the source text into "tokens" first. An identifier that starts with a number looks like a number. Besides 5e3, is a valid number (5000.0) in some languages.
Meanwhile : and . are tokenized as operators. In some contexts an identifier that starts with one of these would lead to ambiguous code. And so forth.
Every language needs to define what is a valid character for an identifier and what is not. Part of the consideration is going to be ease of parsing, part is going to be to avoid ambiguity (in other words even a perfect parsing algorithm couldn't be sure all the time), part is going to be the preference of the language design (in Java's case similarity with C, C++) and some is just going to be arbitrary.
The point is it has to be something, so this is what it is.
For example, are there not numerous times we wish to have objects with these names?
2ndInning
3rdBase
4thDim
7thDay
But imagine when someone might try to have a variable with the name 666:
int 666 = 777;
float 666F = 777F;
char 0xFF = 0xFF;
int a = 666; // is it 666 the variable or the literal value?
float b = 666F // is it 666F the variable or the literal value?
Perhaps, one way we might think is that variables that begin with a numeral must end with an alphabet - so long as
it does not start with 0x and end with a letter used as a hexadeciamal digit, or
it does not end with characters such as L or F,
etc, etc.
But such rules would make it really difficult for programmers as Yogi Berra had quipped about - how could you think and hit at the same time? You are trying to write a computer programme as quickly and error free as possible and then you would have to bother with all these little bits and pieces of rules. I would rather, as a programmer, have a simple rule on how variables should be named.
In my efforts using lexers and regexp to parse data logs and data streams for insertion into databases, I have not found having a keyword or variable beginning with a numeral would make it anymore difficult to parse - so long there are as short a path as possible to remove ambiguity.
Therefore, it is not so much as making it easier for the compiler but for the programmer.
The order seems odd because in regular Java the return type is always specified first. As in:
public static double sum(Iterable<Number> nums) { ... }
Why then, in the Function and BiFunction classes has the choice been made to specify them the other way around? As in:
interface Function<T,R>
interface BiFunction<T,U,R>
I'm not asking here for opinions as to which is better, but specifically:
a) Is there any technical or other (non-stylistic) benefit in preferring one order over the other? Or is it an arbitrary choice?
b) Is anyone aware of any documented explanation, or any stated reason from an authoritative source, why one was chosen over the other?
Aside: the order seems even more odd if extended to higher arities. For example, a hypothetical QuadFunction:
interface QuadFunction<A,B,C,D,R> { ... }
(At the time of writing the highest arity in the library is 2 - i.e. BiFunction.)
See: http://download.java.net/jdk8/docs/api/java/util/function/package-summary.html
It is to be consistent with prior existing notation.
The mathematical integer division function extended into the rational numbers:
(\): I x I -> Q
Functional programming version of the above (like Haskell, Ocaml)
division :: Integer -> (Integer -> Rational)
or
division :: Integer -> Integer -> Rational
All three say "the division function takes two integers and returns a rational number". It is backwards, in a functional paradigm, to say your returns first. C has taught us to say "we return a rational number in the division function, which takes two integers" (ex float division(int a, int b){}).
In Java, your return type is on the left of methods because Java wants to look like C. The designers of C thought "int main(int argv, char *argv[])" looked better than "main(int argv, char *argv[]) int". When writing code, atleast for me, I more often than not know what a method will return before I know what it will need. (edit 1: and we write lines like String s=removeSpaces(textLine), so the return on the left matches the variable on the left)
In C#, func looks the same way as the Java 8 Function.
My guess is that it's more intuitive for method chaining which might be a typical use case for lambdas, i.e.
IntStream.range(1, 10).map(Ints::random).filter(x -> x % 2 == 0)
So, method sequense here reads left to right and lambdas go left to right. So why not having the type params go left to right?
Escalating this a bit further - the reason might be that the English language reads left to right. :-)
UPDATE
I was very surprised to find out that this is something which takes place for maths modern arabic notation:
Latin complex numbers
Arabic complex numbers
In this example arabic notation in every char mirrors latin. One can track this by the angle sign and i (imagenary unit) char - in both cases it has a dot. In the linked wiki article there is also an example of a reversed lim arrow (compared to Java 8 lamda's arrow direction). This could mean that arabic Java, if it was ever developed, would look a bit differently. :-)
Disclaimer: I have background in maths, but I had no idea of the arabic notation when I was answering this question.
In ordinary procedural and OO programming, functions/methods generally take a list of parameters and return some result:
int max(int num1, int num2)
When rewriting function signatures as callback-based (such as for parallel or asynchronous processing), it has been a longstanding practice to convert the signature by appending the return callback as the last parameter:
void maxAsync(int num1, int num2, Callback<int> callback) // pseudo-Java
A current example of this pattern can be found in GWT RPC processing.
This style originated in the Lisp style of languages with the so-called continuation-passing style, where functions are chained by passing a function to a function as a parameter. Since in Lisp arguments are evaluated left-to-right, the function that's consuming the values needs to be at the end of the list. This arrangement has been adopted by imperative languages for continuity and because it's been traditional to tack on additional optional parameters (boolean flags and the like) at the end of the parameter list.
It is the explicit intent to make it more convenient to program in a functional style in Java. Now, in mathematics, a function is generally written like
f: A -> B
(i.e., a function from As to Bs). This corresponds also to the notation in functional languages, Scala and already existing functional libraries for Java.
In other words: it is just the right thing.
Note that a functional interface is not a method and a method is not a functional interface, hence it is not clear what the syntax of the former has to do with the latter.
Just my opinion: to look the same way as Function in guava does. Having the order the other way around would cause a lot of confusion I guess.
http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/base/Function.html
The problem:
I want users to be able to write conditions in a simple syntax in a text editor, as in:
A?outcome1:(B?outcome2:outcome3)
A and B are boolean conditions. So the sentence above means: if A is true, then outcome1, else if B is true, then outcome 2, else outcome3.
In Java, I implement an interpreter of this syntax so that A, B, outcome1, outcome2,outcome3 get translated in values that are pre-stored somewhere (A and B will be functions returning a boolean, outcomes will be objects), and the condition is evaluated and a result is returned.
My question is, am I reinventing the wheel here? Are there Java packages or libraries that already provide neat implementations of "[constrained] natural language interpreted to Java code" kind of functions?
Thx!
I ended up writing a class in Java that reads a human-written rule and interprets it. Find it here:
https://github.com/seinecle/Umigon/blob/master/src/java/RuleInterpreter/Interpreter.java