
javacc-7.0.3.examples.GUIParsing.TokenMgrVersion.CalcInput.jj Maven / Gradle / Ivy
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*
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* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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*/
options {
USER_CHAR_STREAM = true;
BUILD_PARSER = false;
}
PARSER_BEGIN(CalcInputParser)
public class CalcInputParser {
}
PARSER_END(CalcInputParser)
/**
* This example shows an elaborate example to construct a Finite Automaton
* where for every character, there is a move.
*/
TOKEN_MGR_DECLS:
{
/**
* A pointer to the GUI object.
*/
static CalcGUI gui;
/**
* Holds the result of the expression evaluation so far.
*/
static double result = 0.0;
/**
* Flag to indiate the very first operand so that the correct result
* is displayed in this case.
*/
static boolean firstOperand = true;
/**
* Shows the result after a particular operation.
*/
private static void ShowResult()
{
if (firstOperand)
{
image.setLength(image.length() - 1);
if (image.length() > 0)
result = Double.valueOf(image.toString()).doubleValue();
else
result = 0.0;
firstOperand = false;
}
gui.print(result);
}
}
/**
* The first operand
*/
MORE :
{
< ["0"-"9"] >
|
"." : REQUIRED_DIGIT
}
/**
* This state is entered when we need to get at least one digit (after a .)
*/
MORE:
{
< ["0"-"9"] > : OPTIONAL_DIGIT
}
/**
* FA for (["0"-"9"])*.
*/
MORE:
{
< ["0"-"9"] >
}
/**
* You can get an operator at any time (in any lexical state), except when
* a digit is required (afdter a .). Then just go to a state where the next
* operand is scanned (for that particular operator).
*/
SKIP:
{
{ ShowResult(); } : SEEN_PLUS
|
{ ShowResult(); } : SEEN_MINUS
|
{ ShowResult(); } : SEEN_STAR
|
{ ShowResult(); } : SEEN_SLASH
}
/**
* If you get a = in any state, just display the current result.
*/
SKIP:
{
{ ShowResult(); } : OP_OR_OPERAND
}
/**
* Here you can either give an operand (to start a new expression) or give
* an operator that works on the current result.
*/
SKIP:
{
<"=">
}
MORE:
{
< ["0"-"9"] > { firstOperand = true; } : OPERAND
|
"." { firstOperand = true; } : REQUIRED_DIGIT
}
MORE:
{
< ["0"-"9"] > : ADD_RIGHT_OPERAND
|
"." : ADD_REQUIRED_DIGIT
}
MORE:
{
< ["0"-"9"] > : DO_ADD
}
SKIP:
{
< "" >
{ result += Double.valueOf(image.toString()).doubleValue(); } : OP_LOOP
}
MORE:
{
< ["0"-"9"] > : SUB_RIGHT_OPERAND
|
"." : SUB_REQUIRED_DIGIT
}
MORE:
{
< ["0"-"9"] > : DO_SUB
}
SKIP:
{
< "" >
{ result -= Double.valueOf(image.toString()).doubleValue(); } : OP_LOOP
}
MORE:
{
< ["0"-"9"] > : MUL_RIGHT_OPERAND
|
"." : MUL_REQUIRED_DIGIT
}
MORE:
{
< ["0"-"9"] > : DO_MUL
}
SKIP:
{
< "" >
{ result *= Double.valueOf(image.toString()).doubleValue(); } : OP_LOOP
}
MORE:
{
< ["0"-"9"] > : DIV_RIGHT_OPERAND
|
"." : DIV_REQUIRED_DIGIT
}
MORE:
{
< ["0"-"9"] > : DO_DIV
}
SKIP:
{
< "" >
{ result /= Double.valueOf(image.toString()).doubleValue(); } : OP_LOOP
}
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