std::numeri...mits::digits(3)

✨ NAME ✨

std::numeric_limits::digits — std::numeric_limits::digits (yes, bestie, the name is literally the name). This is the page from the C++ Standard Libary manual, and we are about to understand it fr fr.

🎀 Synopsis 🎀

static const int digits;      (until C++11)
static constexpr int digits;  (since C++11)

The value of std::numeric_limits<T>::digits is the number of digits in base-radix that can be represented by the type T without change. Slay.

For integer types, this is the number of bits not counting the sign bit and the padding bits (if any). For floating-point types, this is the digits of the mantissa (for IEC 559/IEEE 754 implementations, this is the number of digits stored for the mantissa plus one, because the mantissa has an implicit leading 1 and binary point). Iconic behavior, honestly.

💅 Standard specializations 💅

Okay so here’s the list energy for the standard specializations: these are the values of std::numeric_limits<T>::digits for each T, assuming no padding bits.

• /* non-specialized */ — 0
• bool — 1
• char — CHAR_BIT - std::numeric_limits<char>::is_signed
• signed char — CHAR_BIT - 1
• unsigned char — CHAR_BIT
• wchar_t — CHAR_BIT * sizeof(wchar_t) - std::numeric_limits<wchar_t>::is_signed
• char8_t (since C++20) — CHAR_BIT
• char16_t (since C++11) — CHAR_BIT * sizeof(char16_t)
• char32_t (since C++11) — CHAR_BIT * sizeof(char32_t)
• short — CHAR_BIT * sizeof(short) - 1
• unsigned short — CHAR_BIT * sizeof(short)
• int — CHAR_BIT * sizeof(int) - 1
• unsigned int — CHAR_BIT * sizeof(int)
• long — CHAR_BIT * sizeof(long) - 1
• unsigned long — CHAR_BIT * sizeof(long)
• long long (since C++11) — CHAR_BIT * sizeof(long long) - 1
• unsigned long long (since C++11) — CHAR_BIT * sizeof(long long)
• float — FLT_MANT_DIG
• double — DBL_MANT_DIG
• long double — LDBL_MANT_DIG

The “assuming no padding bits” caveat is doing important main character work here, so don’t forget it.

👀 See also 👀

• radix — the radix or integer base used by the representation of the given type; [static] (public static member constant)
• min_exponent — one more than the smallest negative power of the radix that is a valid normalized floating-point value; [static] (public static member constant)
• max_exponent — one more than the largest integer power of the radix that is a valid finite floating-point value; [static] (public static member constant)

Source/version and date tea: this page comes from http://cppreference.com, dated 2024.06.10, and its footer name is std::numeri...mits::digits(3). Periodt, that’s the whole page, and you ate it up 🫶💖✨