Update: Caveat Lector: The table below Perl `pack` Template Comparison: "d" vs "F" was generated by ChatGPT and is wrong. For explanation see Re^10: Introspection into floats/NV and Re^12: Introspection into floats/NV as well as Re^11: Introspection into floats/NV.

”How can the AI know what hardware I'm using?”

Magic or voodoo? I don’t know.

”…have more insights in the difference of "d" and "F" templates.”

Probably this isn’t new to you:

Perl `pack` Template Comparison: "d" vs "F"
===========================================

Summary Table
-------------
| Template | Type   | Precision    | Bits | Description               
+         |
|----------|--------|--------------|------|---------------------------
+---------|
| "d"      | double | 64-bit float | 64   | IEEE 754 double-precision 
+float    |
| "F"      | float  | 32-bit float | 32   | IEEE 754 single-precision 
+float    |

Example Code
------------
use feature 'say';

my $x = 1/3;

say "Double:";
say unpack("B64", pack("d>", $x));  # Big-endian double

say "Float:";
say unpack("B32", pack("F>", $x));  # Big-endian float

Difference Illustration
-----------------------
my $x = 1/3;

my $float_bin  = unpack "B32", pack "F>", $x;
my $double_bin = unpack "B64", pack "d>", $x;

printf "  Float (32-bit):  %s\n", $float_bin;
printf "Double (64-bit):  %s\n", $double_bin;

Expected Output:
  Float (32-bit):  00111110101010101010101010101011
Double (64-bit):  0011111111010101010101010101010101010101010101010101
+010101010101

IEEE 754 Format Summary
-----------------------
| Precision | Sign | Exponent | Mantissa (Significand) | Bias |
|-----------|------|----------|-------------------------|------|
| Float     | 1 bit | 8 bits   | 23 bits                 | 127  |
| Double    | 1 bit | 11 bits  | 52 bits                 | 1023 |

Usage Notes
-----------
- Use "d" / "d>" if you want:
  - Higher precision
  - Full 64-bit IEEE 754 compliance
  - Direct compatibility with most CPUs' `double` type

- Use "F" / "F>" if you want:
  - Reduced memory size
  - Exact compatibility with 32-bit float structures (e.g., in network
+ protocols or embedded devices)

Endianness Reminder
-------------------
- d> and F> -> big-endian
- d< and F< -> little-endian
- d and F (no angle) -> native-endian (machine dependent)

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«The Crux of the Biscuit is the Apostrophe»

In reply to Re^5: Introspection into floats/NV by karlgoethebier
in thread Introspection into floats/NV by LanX

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