Arithmetic Expression validation

Can somebody help me in giving me a java program which can
validate an arithmetic expression.
For eg ( A + b1 ) / (2 * c) + d
If someone already has a code snippet which takes an expression String
and returns a boolean which tells if the expression is valid or not, please post it..... My project is running out of coding time :))))

With due respect....Its not the question of not trying
it.. I just thought it would not be judicious to
re-invent the wheel. Depends on what you are doing.
If you are working in industry, or are doing a final year project, code re-use is an excellent time saver.
If you are doing homework which asks you to write an equation validator, code re-use is pretty much cheating. If you did this, you might as welll let the brightets person in the class write the code, and everyone else hand in the same code.

Similar Messages

Regular expressions to parse arithmetic expression

Hello,
I would like to parse arithmetic expressions like the following
"5.2 + cos($PI/2) * -5"where valid expression entities are numbers, operations, variables and paranthesis. Until now I have figured out some regular expressions to match every type of entities that I need, and combine them into one big regex supplied to a pattern and matcher. I will paste some code now to see what I wrote:
public class RegexTest {
    /** A regular expression matching numeric expressions (floating point numbers) */
    private static final String REGEX_NUMERIC = "(-?[0-9]+([0-9]*|[\\.]?[0-9]+))";
    /** A regular expression matching a valid variable name */
    private static final String REGEX_VARIABLE = "(\\$[a-zA-Z][a-zA-Z0-9]*)";
    /** A regular expression matching a valid operation string */
    public static final String REGEX_OPERATION = "(([a-zA-Z][a-zA-Z0-9]+)|([\\*\\/\\+\\-\\|\\?\\:\\@\\&\\^<>'`=%#]{1,2}))";
    /** A regular expression matching a valid paranthesis */
    private static final String REGEX_PARANTHESIS = "([\$\$])";
    public static void main(String[] args) {
        String s = "5.2 + cos($PI/2) * -5".replaceAll(" ", "");
        Pattern p = Pattern.compile(REGEX_OPERATION + "|" + REGEX_NUMERIC + "|" + REGEX_VARIABLE + "|" + REGEX_PARANTHESIS);
        Matcher m = p.matcher(s);
        while (m.find()) {
            System.out.println(m.group());
}The output is
5
2
+
cos
$PI
2
5There are a few problems:
1. It splits "5.2" into "5" and "2" instead of keeping it together (so there might pe a problem with REGEX_NUMERIC although "5.2".matches(REGEX_NUMERIC) returns true)
2. It interprets "... * -5" as the operation " *- " and the number "5" instead of " * " and "-5".
Any solution to solve these 2 problems are greately appreciated. Thank you in advance.
Radu Cosmin.

cosminr wrote:
So, I've written some concludent examples and the output after parsing (separated by " , " ):
String e1 = "abs(-5) + -3";
// output now: abs , ( , - , 5 , ) , + , - , 3 ,
// should be: abs , ( , -5 , ) , + , - , 3 , (Notice the -5)
I presume that should also be "-3" instead of ["-", "3"].
String e2 = "sqrt(abs($x=1 + -10))";
// output now: sqrt , ( , abs , ( , $x , = , 1 , + , - , 10 , ) , ) ,
// should be: sqrt , ( , abs , ( , $x , = , 1 , + , -10 , ) , ) ,   (Notice the -10)
String e3 = "$e * -1 + (2 - sqrt(4))";
// output now: $e , * , - , 1 , + , ( , 2 , - , sqrt , ( , 4 , ) , ) ,
// should be: $e , * , -1 , + , ( , 2 , - , sqrt , ( , 4 , ) , ) ,
String e4 = "sin($PI/4) - 3";
// output now: sin , ( , $PI , / , 4 , ) , - , 3 , (This one is correct)
String e5 = "sin($PI/4) - -3 - (-4)";
// output now: sin , ( , $PI , / , 4 , ) , - , - , 3 , - , ( , - , 4 , ) ,
// should be: sin , ( , $PI , / , 4 , ) , - , -3 , - , ( , -4 , ) , (Notice -3 and -4)I hope they are relevant, If not I will supply some more.I made a small change to REGEX_NUMERIC and also put REGEX_NUMERIC at the start of the "complete pattern" when the Matcher is created:
import java.util.regex.*;
class Test {
    private static final String REGEX_NUMERIC = "(((?<=[-+*/(])|(?<=^))-)?\\d+(\\.\\d+)?";
    private static final String REGEX_VARIABLE = "\\$[a-zA-Z][a-zA-Z0-9]*";
    public static final String REGEX_OPERATION = "[a-zA-Z][a-zA-Z0-9]+|[-*/+|?:@&^<>'`=%#]";
    private static final String REGEX_PARANTHESIS = "[()]";
    public static void main(String[] args) {
        String[] tests = {
            "abs(-5) + -3",
            "sqrt(abs($x=1 + -10))",
            "$e * -1 + (2 - sqrt(4))",
            "sin($PI/4) - 3",
            "sin($PI/4) - -3 - (-4)",
            "-2-4" // minus sign at the start of the expression
        Pattern p = Pattern.compile(REGEX_NUMERIC + "|" + REGEX_OPERATION + "|" + REGEX_VARIABLE + "|" + REGEX_PARANTHESIS);
        for(String s: tests) {
            s = s.replaceAll("\\s", "");
            Matcher m = p.matcher(s);
            System.out.printf("%-21s-->", s);
            while (m.find()) {
                System.out.printf("%6s", m.group());
            System.out.println();
}Note that since Java's regex engine does not support "variable length look behinds", you will need to remove the white spaces from your expression, otherwise REGEX_NUMERIC will go wrong if a String looks like this:
"1 - - 1"Good luck!

Inline display of error message for a regular expression validation

Hi All,
I am using ApexLib in my application.
I am using regular expression validation for some of the items.
Those validation will happen when the button is pressed and the message will be displayed as per the error.
But, I want the errors to be displayed immediately when the focus is away from that item.
as we do for required items.
could anybody help me to achieve it?
Thanks in advance
bye
Srikavi

Hi Srikavi,
to achieve a Validation of an item when leaving the field you'll have to use some javascript code (as ApexLib does internally).
What do you need:
- onChange - Event on your Item
- some Javascript code which is called in the onChange Event (you can put this code either in your page html header or, if it is used more often in your application, in a seperate js File)
- call the ApexLib method apexlib.error.showError to display your error
I actually never tried it myself, but i'm pretty sure that this will work (according to what i've seen in the ApexLib code).
Have fun and tell us how it went,
Peter
Edited by: peter_raganitsch on Sep 5, 2008 11:56 AM

"ABAP Basics" Book - arithmetic expression error in the sample code

Hi all,
I have just started learning ABAP on mini SAP system (NW7.01) by following "ABAP Basics" book.
This question might be a FAQ, but I have spent a few days searching a right answer without success.
I appreciate if you could help me on this.
On the page 162, there is a function module sample, which contains the line as following:
e_amount = i_km * '0.3'.
Here l_km (import) is type of i, and e_amount (export) is type of f.
Though I do not think of any problem with this line, it throws an arithmetic expression error when executed directly for testing as well as when called from a program.
When I tried a similar thing in a program, it was fine.
However within a function module it throws this error.
Thanks in advance.
Terry

Like I said before, I do not think any problem about the code itself.
I suspect some environmental things?
I should have mentioned SAP mini system NW7.01 is running on Vista Business?
To be specifc, I receive this message:
Arithmetic operations are only expected for operands that can be converted to numbers.
(numeric operands). - (numeric operands). - - - -
with the following function module:
[code]
FUNCTION ZPTB00_CALCULATE_TRAVEL_EXPENS.
""Local Interface:
*" IMPORTING
*"     VALUE(I_KM) TYPE REF TO I
*" EXPORTING
*"     VALUE(E_AMOUNT) TYPE REF TO F
*" EXCEPTIONS
*"      FAILED
e_amount = i_km * '0.3'.
IF sy-subrc <> 0.
RAISE failed.
ENDIF.
ENDFUNCTION.
[/code]

Expression validation error

While trying to validate expression in mapping error window popups:
"java.lang.Exception: ValidationError??
java.lang.Exception: API8532: Internal Error: Language Validation can't create a unique type name when attempting to deploy a validation package."
OWB creates "owb\bin\admin\..0" file, in which there are such entries:
Wed May 21 08:14:40 CEST 2003
Executing SQL for Expression Validation:
CREATE TYPE "INGRP1_T_0";
Wed May 21 08:14:40 CEST 2003
Executing SQL for Expression Validation:
CREATE TYPE "INGRP1_T_1";
Wed May 21 08:14:40 CEST 2003
Executing SQL for Expression Validation:
CREATE TYPE "INGRP1_T_2";
and so on up to :
"Executing SQL for Expression Validation:
CREATE TYPE "INGRP1_T_50";
Wed May 21 08:14:42 CEST 2003
java.lang.Exception: ValidationError??
java.lang.Exception: API8532: Internal Error: Language Validation can't create a unique type name when attempting to deploy a validation package.
"owb\bin\admin\ValidationPLSQL.log" file contains these 51 commands with increasing number:
CREATE TYPE "INGRP1_T_0";
It doesn't matter what expression I define.
OWB is 9.0.4, Database EE 9.0.2
What can it be ?

Problem is it is already set to English_United States, I work only on this locale as to avoid such situations. MLS Disp. Lang. is American English.
NLS settings in database and local regional settings in client system are only different (local).
I tried validation at home, on different repository and it worked. Both databases are EE 9.2.0.1, the only real difference is server platform (Win XP there vs Linux).
From what I can see right now there are way too many problems with OWB and locales, will it be fixed in the upcoming release ?
Regards,
Piotr

Eclipse XQuery expression validation failed: The current configuration is out of sync with the XQuery resource in the repository.

I created a wsdl based on a dbadapter in jdeveloper, imported into eclipse and created the biz and the proxy and uploaded to oracle service bus, it works fine,
but happens now that i need to have a xsd and wsdl with business names and not table names, invented to create a xsd and wsdl file in jdeveloper
and then went to eclipse and tried t xquery tranformation, but when i add the replace in the message flow in the filed in Variable : body and Expression i look for the xquery and in the binding trying to put
$body/input parameter, get the following error [RouteNode1, Replace action] XQuery expression validation failed: The current configuration is out of sync with the XQuery resource in the repository.
what im doing wrong or its configuration
thanks in advance sonia

thanks
ok have created a table with only in column varchar2(1)
then the type object and the procedure to insert it works the proxy in the osb if i test it inserts
now in jdeveloper i created an xml file with
<?xml version="1.0" encoding="windows-1252" ?>
<vessel>
<barco>a</barco>
</vessel>
then i created a xsd based on this xml, and a wsdl based on the xsd
in eclipse created a xquery transformation and selected source as the xsd created in adf and target the xsd input parameter, dont know why in the purple ball of the input parameter it puts a ?, an a f.
then in the proxy xpath not writing anything in variable body and in the expression select the xquery and in binding select the parameter

Need help regarding Arithmetic Expressions

Hi Experts,
I have a requirement where in I need to pass Arithmetic Expressions (+,-,/) as constants to a subroutine.For ex:
constants:c_p   type char1 value '+',
                 c_m   type char1 value '-',
data:v_a type char1 value '2',
         v_b type char1 value '6',
        v_r    type string.
v_r = v_ a   + v_b.
In the above instead of + I want use c_p.Please help me out is there any other way in defining Arithmetic expresiions where I could use constants or variables instead of directly using these expressions(+,-).Thanks in advance.
With Regards,
Srini..

Hello Srini,
I think you must have a look at the FMs belonging to FuGr. CALC.
For e.g., EVAL_FORMULA which evaluates Literal or Variable formulas
CONSTANTS:
C_P TYPE CHAR1 VALUE '+',
C_M TYPE CHAR1 VALUE '-'.
DATA:
V_A TYPE CHAR1 VALUE '2',
V_B TYPE CHAR1 VALUE '6',
V_FORMULA TYPE STRING,
V_RES_F   TYPE F,
V_RES_P   TYPE P.
CONCATENATE V_A C_P V_B INTO V_FORMULA SEPARATED BY SPACE.
CALL FUNCTION 'EVAL_FORMULA'
EXPORTING
    FORMULA                 = V_FORMULA
IMPORTING
    VALUE                   = V_RES_F
EXCEPTIONS
    DIVISION_BY_ZERO        = 1
    EXP_ERROR               = 2
    FORMULA_TABLE_NOT_VALID = 3
    INVALID_EXPRESSION      = 4
    INVALID_VALUE           = 5
    LOG_ERROR               = 6
    PARAMETER_ERROR         = 7
    SQRT_ERROR              = 8
    UNITS_NOT_VALID         = 9
    MISSING_PARAMETER       = 10
    OTHERS                  = 11.
IF SY-SUBRC = 0.
MOVE V_RES_F TO V_RES_P.
WRITE: V_RES_P .
ENDIF.
BR,
Suhas

Add spaces in arithmetic expressions

Hi experts,
i have to insert spaces in arithmetical expressions written by users.
For example:
INPUT (by USERS): A+B-SQRT(C)/(D**2)
OUTPUT (by Program): A + B - SQRT( C ) / ( D ** 2 )
Possible arithmetic operators are:
+; - ; *; /; **; SQRT()
Any hints will be rewarded.
Thanks in advance.
Fabio.

Thanks to all guys!
the right code is a mixt of yours hints:
l_len = STRLEN( tb_mzcatc-/bic/zformatc ).
DO.
    l_char = input+n(1).
    CASE l_char.
      WHEN 'Q' OR
           'R'.
        CONCATENATE formula l_char INTO formula.
      WHEN 'T'.
        l_char = input+n(2).
        CONCATENATE formula l_char INTO formula.
        n = n + 1.
      WHEN '*'.
        IF input+n(2) = '**'.
          l_char = input+n(2).
          CONCATENATE formula l_char INTO formula SEPARATED BY ' '.
          n = n + 1.
        ELSE.
          CONCATENATE formula l_char INTO formula SEPARATED BY ' '.
        ENDIF.
      WHEN OTHERS.
        CONCATENATE formula l_char INTO formula SEPARATED BY ' '.
    ENDCASE.
    n = n + 1.
    IF n GT l_len.
      EXIT.
    ENDIF.
ENDDO.
Message was edited by:
        Fabio Cappabianca

Reset Item After Regular Expression Validation Fails

Apex 4.2
I have a page item (P1_MYITEM) that should only hold alpha charaters, so I have created an item regular expression validation
using
^[a-zA-Z]+$
This works well, but now I want to reset my item (P1_MYITEM) to null
if the validation fails.
Tried using a page process, but they do not run if the validation fails.
Any ideas ?
Gus

Got it working using
Begin
if not regexp_like (:P1_MYITEM, '^[a-zA-Z]+$')
    then
      APEX_UTIL.SET_SESSION_STATE('P1_MYITEM',NULL);
      return 'Country must be text characters only.';
end if;
End;

Regular Expression Validator - want to edit an object acct field

The field is a character field. But the field must be editted as follows:
Field must either be 4 numeric numbers with the first position always an 8 so it could be a range from 8000 to 8999
But I must also allow them to enter "8%" or "8n%" or "8nn%" where n represents a number. They want me to allow wild cards.
How would I define this edit on the same field.
1) First Validation: If it has a "%" then the first digit must be an 8 then I can have any of the wild card combinations given above.
2) Second Validation: If no wild card then the field must be in the range from 8000-8999
Is this validation a candidate for Regular Expression Validator or for my own custom method.
If I can code this as a regular expression validator how would I code it. I spent the last day looking on the web for Regular Expression Validator examples.

I get the following errors that occur. I can key 8% or 8ddd but when I try these combinations 8d% or 8dd% then the following errors pop up. It gives multiple error but I am just keying on a single line. I can add multiple object lines but just one at a time.
java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
java.lang.reflect.InvocationTargetException at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
- JBO-ObjectCode_Rule_1: Object must be in range 8000-8999 or object must be in form of 8%, 8n%, 8nn% where n represents a number.
- JBO-27008: Attribute set for ObjectCode in view object AccountsecuritygroupobjView2 failed
- JBO-ObjectCode_Rule_1: Object must be in range 8000-8999 or object must be in form of 8%, 8n%, 8nn% where n represents a number.
- JBO-ObjectCode_Rule_1: Object must be in range 8000-8999 or object must be in form of 8%, 8n%, 8nn% where n represents a number.
- JBO-27008: Attribute set for ObjectCode in view object AccountsecuritygroupobjView2 failed
- JBO-ObjectCode_Rule_1: Object must be in range 8000-8999 or object must be in form of 8%, 8n%, 8nn% where n represents a number.

Regular Expression Validator Problem

Hi,
I have a text area that I want to use a regular expression
validator on to verify that one or more 9 char alphanumeric serial
numbers were entered.
<mx:RegExpValidator
source="{entryField}"
property="text"
flags="gi"
expression="{/[a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0-9][a-zA-Z0- 9][a-zA-Z0-9][a-zA-Z0-9](
|,|\\n|\\r|\\t)/}"
valid="handleResult(event)"
invalid="handleResult(event)"
trigger="{entryField}"
triggerEvent="textInput"
/>
//for testing
private function
handleResult(eventObj:ValidationResultEvent):void {
if (eventObj.type == ValidationResultEvent.VALID)
entryField.setStyle("borderColor", "green");
entryField.setStyle("borderThickness", "2");
else
entryField.setStyle("borderColor", "red");
entryField.setStyle("borderThickness", "2");
The problem is the handler function always comes back
invalid, even when it should be valid, such as: 123456789 a12345678
lk231jkop
Can anyone advise where I might be going wrong?
Thanks!

This is weird, i just tried your RegExp using the Adobe's
Live Docs example and it worked perfectly.
Try it at:
http://livedocs.adobe.com/flex/201/langref/mx/validators/RegExpValidator.html
Scroll down to the end of the page, then type your RegExp and
your TestValue and click the Validate button, it works. I am
guessing that maybe it is your
i
flag, try removing it from your validator.
Hope this helps

Regex for arithmetic expressions

Hi all,
I am new to Java. I was wondering if anyone can help me understand how regular expressions work. My problem is how to come up with a regular expression that would match a simple arithmetic expression like:
a + b + c + d
And I want to capture things by groups. I largely suspect that I should use something like:
(\\w+)(\\s\\+\\s(\\w+))*
(I use the \\s here because \\b doesn't seem to work)
would work by capturing the first word like sequence with (\\w+), and the succeeding repeats of the plus sign and another word being captured by (\\s\\+\\s(\\w+))*. Didn't work though. Can anyone tell me what's wrong and how to think of a better way of handling these sort of expressions?
The code I tried goes like:
String patt = "(\\w+)(\\s\\+\\s(\\w+))*";
String feed = "a + b + c + d";
Pattern p = Pattern.compile(patt);
Matcher m = p.matcher(feed);
/* here I want to see if the groupings work somehow*/
if(m.find()){
for(int i=0; i<=m.groupCount(); i++)
System.out.println(m.group(i));
Thanks

Sorry about that. Here's the correctly formatted post:
So, with a simple arithmetic expression like:
a + b + c + dI want to capture things by groups and I thought of using something like:
(\\w+)(\\s\\+\\s(\\w+))*(I use the \\s here because \\b doesn't seem to work)
with the idea of capturing the first word like sequence with (\\w+), and the succeeding repeats of the plus sign and another word being captured by (\\s\\+\\s(\\w+))*. As this didn't work, can anyone tell me what's wrong and how to think of a better way of handling these sort of expressions?
The code I tried goes like:
String patt = "(\\w+)(\\s\\+\\s(\\w+))*";
String feed = "a + b + c + d";
Pattern p = Pattern.compile(patt);
Matcher m = p.matcher(feed);then I want to see if the groupings work somehow
if(m.find()){
for(int i=0; i<=m.groupCount(); i++)
System.out.println(m.group(i));
}and yes, I am wondering if arithmetic parsing would be possible with regex. I have implemented something similar before using combinations of simple tokenization and character checks, but I want to make cleaner looking code. Would using regular expressions be a bad choice? What if I feed something like:
(a + b) + (c + d)

Thread to evaluate arithmetic expressions

I'm trying to write a program that evalutaes arithmetic expression concurrently using Java concurency primitives. The idea behind the threading is to avoid multiple evaluations of common subexpression. I have attached the code that I have written so far but was hoping someone could offer me a hand with the evaluate() and run() methods contained at the end of the program. Thanks.
public class Example {
     public static void main(String[] args) {
          BinaryOp plus = new BinaryOp() {
               public int apply(int n1, int n2) {
                    return n1 + n2;
          BinaryOp times = new BinaryOp() {
               public int apply(int n1, int n2) {
                    return n1 * n2;
          Arith e1 = new Operator(plus, new Number(4), new Number(5));
          Arith e2 = new Operator(plus,new Operator(times, new Number(3), e1),
               new Operator(plus, e1, new Number(6)));
          Arith e3 = new Operator(times, e2, e2);
          System.out.println(e3.evaluate());
interface BinaryOp {
     // An operator that can be applied to two numbers
     int apply(int n1, int n2);
interface Arith {
     // An arithmetic expression that can be evaluated.
     int evaluate();
class Number implements Arith {
     private int n;
     Number(int n) {
          this.n = n;
     public int evaluate() { // A number evaluates to itself.
          return n;
class Operator implements Arith, Runnable {
     private BinaryOp op;
     private Arith e1;
     private Arith e2;
     private boolean done = false;
     private int result = 0; // holds the result of previous evaluation
     Operator(BinaryOp op, Arith e1, Arith e2) {
          this.op = op;
          this.e1 = e1;
          this.e2 = e2;
          (new Thread(this)).start();
     public int evaluate() {
     public void run() {
}

I'm trying to write a program that evalutaes arithmetic expression
concurrently using Java concurency primitives. The idea behind the
threading is to avoid multiple evaluations of common subexpression. Interesting ... the main problem however is to find those common
subexpressions. Most of the evaluation of those common subexpressions
can be done in the parse/compile phase though, effectively elliminating
the need for threads, e.g. (foo+bar)-(foo+bar) can be deduced to be
equal to zero if both 'foo' and 'bar' happen to referential transparent,
i.e. they don't have side effects.
What you're doing now is just starting a new thread for every binary operator.
This is, most likely, not what you want. The strategy of what thread to
start for which subexpression must have layed out the sequence of
threads to start before actual evaluation is started (also see above).
kind regards,
Jos

Fully parentized arithmetic expression

Hi,
Would any one be able to tell how does following fully parentized arithmetic expression turns 28?
I don't get it.
As an example of using identifiers and assignment, consider the FPAE
(x0 = ((3 + (x1 = 4)) * x1))
This expression evaluates to 28 and has the side effects of making the values associated to x0 and x1 28 and 4, respectively. Hence, if the next FPAE to be evaluated were
(x1 = (x0 - x1))
the result would be 28 - 4, or 24, and, as a side effect, the value of x1 would be changed to 24. The intent, then, is for identifiers to retain their values (or to have them changed, via assignment) as evaluation continues from one FPAE to another.
Thanks

(x0 = ((3 + (x1 = 4)) * x1))
3+(x1=4)At this point x1 = 4 so the value is 7.
(3+(x1=4))*x1x1 is still 4, so 7 x 4 = 28.
Operands are evaluated strictly left to right.

Arithmetic expression performance

Hi,
Is there any difference in arithmetic expression evaluation performance between one big expression and several smaller that save their partial results in variables?
For example: Which solution will work faster:
1)
int i;
for(i=1000000; i>=0; i--)
x=i*a+b*c; //a, b, c - some variables
}2) int i,p1, p2;
for(i=1000000; i>=0; i--)
//a, b, c - some variables
p1 = i*a;
p2 = b*c;
x[i] = p1+p2;

I some cases I can replace a division with a multiplication.
Instead of:
for(int i=0; i<1000; i++)
tab=tab[i]/5;
}I can use:int scale = (1<<16)/5;
for(int i=0; i<1000; i++)
tab[i]=(tab[i] * scale)>>16;
}The second solution gives the same result and avoids division by replacing it with multiplication and very fast bit shift operation.
I can see that my problem is wider that I thought. Processor manuals are quite precise, but I'm programming in java, not in assebler. So most important issue for me is the way the JVM implementation will execute each bytecode operation. I think that various JVM for various platforms may execute instructions differently. So I'm looking for general tips which operations should be avoided when performance is the key issue.
I'm writing image processing aplication for mobile devices, so any milisecond counts for me.
I found some java performance tips on the inernet, but, frankly, I don't trust them. For example: It is recommended to avoid 2-dimensional tables and implement them as 1D table. So instead of:int[][] tab = new int[100][100];
tab[x][y] = c;one should use:int[] tab = new int[10000];
tab[y*100+x]=c;It seems reasonable, but the second solution needs multiplication. In the first solution compiler can generate code that store pointers to "second dimension tables" in "first dimension" (table with references to tables). Pointers (references, i mean) have size of 2^n. Integers in second dimension are also of size 2^n. So theoretically compiler may produce byte code that will need no multiplication but only very fast bit-shift operations.
My question is - how does the compiler cope with 2d arrays.

Arithmetic Expression validation

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