mpw-shell/value.h
2016-01-27 10:43:34 -05:00

74 lines
1.1 KiB
C++

#ifndef __value_h__
#define __value_h__
#include <string>
#include <cstdint>
// hold a string and number value.
struct value {
public:
std::string string;
int32_t number = 0;
// empty token treated as 0.
value() : status(valid)
{}
value(const value &) = default;
value(value &&) = default;
value(int32_t n) :
string(std::to_string(n)),
number(n),
status(valid)
{}
value(const std::string &s) : string(s)
{}
value(std::string &&s) : string(std::move(s))
{}
value &operator=(const value&) = default;
value &operator=(value &&) = default;
int32_t to_number() {
if (status == unknown)
scan_number();
if (status == valid) return number;
expect_number();
}
int32_t to_number(int default_value) noexcept {
if (status == unknown)
scan_number();
if (status == valid) return number;
return default_value;
}
bool is_number() noexcept {
if (status == unknown)
scan_number();
return status == valid;
}
private:
[[noreturn]] void expect_number() const;
void scan_number() noexcept;
mutable enum {
unknown,
valid,
invalid
} status = unknown;
};
#endif