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|
// lowest precedence
%token NUMBER // integral numbers
EOLN // newline
%left '+' '-'
%left '*' '/'
%right UNARY
// highest precedence
%%
expressions:
expressions
evaluate
|
prompt
;
evaluate:
alternative
prompt
;
prompt:
{
prompt();
}
;
alternative:
expression
EOLN
{
cout << $1 << endl;
}
|
'q'
done
|
EOLN
|
error
EOLN
;
done:
{
cout << "Done.\n";
ACCEPT();
}
;
expression:
expression
'+'
expression
{
$$ = $1 + $3;
}
|
expression
'-'
expression
{
$$ = $1 - $3;
}
|
expression
'*'
expression
{
$$ = $1 * $3;
}
|
expression
'/'
expression
{
$$ = $1 / $3;
}
|
'-'
expression %prec UNARY
{
$$ = -$2;
}
|
'+'
expression %prec UNARY
{
$$ = $2;
}
|
'('
expression
')'
{
$$ = $2;
}
|
NUMBER
{
$$ = atoi(d_scanner.YYText());
}
;
|
