sunlabs.brazil.util
public class Calculator extends Object
<stmt> ::= <var> = <expr> | <expr>
<expr> ::= <rexpr> | <expr> <bool op> <rexpr>
<bool op> ::= && | <or>
<or> ::= ||
<rexpr> ::= <aexpr> | <rexpr> <rel op> <aexpr>
<rel op> ::= < | <= | > | >= | == | !=
<aexpr> ::= <term> | <aexpr> <add op> <term>
<add op> ::= + | -
<term> ::= <factor> | <term> <mult op> <factor>
<mult op> ::= * | / | %
<factor> ::= <var> | <num> | ! <factor> | ( <expr> )
<var> ::= <letter> | <var> <var2>
<var2> ::= <letterordigit> | . | _
<num> ::= <unum> | + <unum> | - <unum>
<unum> ::= <int> | <int> . | <int> . <int> | . <int>
<int> ::= <digit> | <int> <digit>
A <letter> is defined as a Java char
for which
Char.isLetter(char)
is true
. A
<letterordigit> is defined as a Java char
for which
Char.isLetterOrDigit(char)
is true
. A digit
is defined as a Java char
for which
Char.isDigit(char)
is true
.
Values for <var>
are looked up in the supplied
Dictionary
. If <var>
can not be found,
it is assumed to have the value zero. If the value found is "true" or
"yes" (case insensitive), it is assumed to be one. Similarly, if the
value found is "false" or "no", it is assumed to be zero. Assignment
to <var>
stores the computed value in the same
Dictionary
.
The period in <unum>
, if there is one, must be
immediately adjacent to surrounding <int>
s.
Version: 2.4
Field Summary | |
---|---|
boolean | debugging
Set true for debug output. |
Constructor Summary | |
---|---|
Calculator()
The no argument constructor will create an internal
Hashtable in which it looks up and stores values
associated with variables.
| |
Calculator(Dictionary d)
This constructor will use the Dictionary parameter to
lookup and store values associated with variables.
|
Method Summary | |
---|---|
String | getValue(String stmt)
Computes the value of the statement passed in the parameter
string and returns a string representation of the result.
|
String | getValue(String stmt, Dictionary d)
Computes the value of the statement passed in the parameter
string and returns a string representation of the result.
|
static void | main(String[] args)
A test driver for the calculator. |
void | stringsValid(boolean allStringsValid)
Normally, variables whose values are "on", "yes", or
"true" and converted to "1.0", while the values "off", "no", and
"false" are converted to "0.0". |
true
for debug output. The output probably won't
make sense to anyone other than the author.Hashtable
in which it looks up and stores values
associated with variables.
See Also: java.util.Hashtable
Dictionary
parameter to
lookup and store values associated with variables.
Parameters: d the Dictionary
object
that serves as a symbol table
See Also: java.util.Dictionary
null
is
returned.
Parameters: stmt a string representation of an arithmetic expression or assignment
Returns: a string representation of
the computed result or
null
Throws: ArithmeticException occurs when a result is improper (e.g. infinity) or when the input statement can not be parsed
null
is
returned. The second parameter is used as a symbol table
for the duration of this method call. Note this method is
not thread safe!
Parameters: stmt a string representation of an arithmetic expression or assignment d the temporary symbol table
Returns: a string representation of
the computed result or
null
Throws: ArithmeticException occurs when a result is improper (e.g. infinity) or when the input statement can not be parsed
Parameters: args required signature for
main
method, not used