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关于Basic程序解释器及编译原理的简单化(2)---C++封装好的Basic解释器(8) {
register char op;
int hold;
level3(result,index);
while ((op = *m_tokens.at(*index).token) =='+' op == '-')
{
(*index)++;
level3(&hold,index);
arith(op,result,&hold);
}
}
/* multiply or divide two factors */
void CExecutable::level3(int *result,int *index)
{
register char op;
int hold;
level4(result,index);
while ((op = *m_tokens.at(*index).token) == '*' op == '/' op == '%')
{
(*index)++;
level3(&hold,index);
arith(op,result,&hold);
}
}
/* process integer exponent */
void CExecutable::level4(int *result,int *index)
{
register char op;
int hold;
level5(result,index);
if ((op = *m_tokens.at(*index).token) == '^')
{
(*index)++;
level5(&hold,index);
arith(op,result,&hold);
}
}
/* is a unary + or - */
void CExecutable::level5(int *result,int *index)
{
register char op;
op = 0;
if ((m_tokens.at(*index).token_type==DELIMITER) &&
*m_tokens.at(*index).token == '+'
*m_tokens.at(*index).token == '-' )
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