I want to parse an operator say "+" from the string "+" which i entered as command-line argument at run-time and then add two integers say 'a' and 'b'.
So how can i perform the above task?
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What is the grammar? You need that before parsing.nhahtdh– nhahtdh2013-03-03 08:49:44 +00:00Commented Mar 3, 2013 at 8:49
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1if say i enter "10+20" in commandline then how can i get the answer as "30"?Himanshu Aggarwal– Himanshu Aggarwal2013-03-03 09:03:17 +00:00Commented Mar 3, 2013 at 9:03
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3 Answers
What nobody so far is telling you is that to recognize arithmetic expressions in general you need to use, or write, a parser. Have a look for the Shunting-yard algorithm, recursive descent expression parsing, etc.
1 Comment
Himanshu Aggarwal
ok. i would hav to explore it a little more than.
If you are using Java 1.7, you can use a switch to test for each possible operator and then do the corresponding operation:
switch(operator){
case("+"): result = a + b; break;
case("-"): result = a - b; break;
}
For older versions of Java can be done using if statements.
4 Comments
Mordechai
Or
operator.charAt(0)Himanshu Aggarwal
if say i enter "10+20" in commandline then how can i get the answer as "30"?
JB Nizet
That's another question. Why didn't you ask that?
Himanshu Aggarwal
i thought to try it later on if i could get some hint on this one.
if (string.equals("+")) {
System.out.println("The result is " + (a + b));
}
1 Comment
Himanshu Aggarwal
if say i enter "10+20" in commandline then how can i get the answer as "30"?