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10581 :: Mismatch Nim Documentation Regarding 32-bit Floating-Point Literals.

• AntonioFS (orginal) [2023-10-30T23:40:38+01:00] view original

  Hello.

  Based on the official Nim documentation, I can see there's a mismatch between the documentation and the current functionality of the Nim language regarding floating-point literals. Here's the issue and corresponding examples detailed:

  According to the official Nim documentation, the language is expected to support the following:

  FLOAT32_SUFFIX = ('f' | 'F') ['32']

  FLOAT32_LIT = HEX_LIT ''' FLOAT32_SUFFIX | (FLOAT_LIT | DEC_LIT | OCT_LIT | BIN_LIT) ['''] FLOAT32_SUFFIX

  This suggests that Nim should be able to interpret floating-point literals (FLOAT32_LIT) that are hexadecimal numbers (HEX_LIT), floating-point numbers (FLOAT_LIT), decimal numbers (DEC_LIT), octal numbers (OCT_LIT), or binary numbers (BIN_LIT), followed by an optional suffix indicating it's a 32-bit floating-point literal (FLOAT32_SUFFIX).

  However, in practice, Nim currently doesn't support:

  • Floating-point literals in hexadecimal: HEX_LIT cannot be used with FLOAT32_SUFFIX in Nim. This is mentioned in an open issue in the official Nim repository on GitHub nim-lang.org.

  • Floating-point literals in octal and binary format: OCT_LIT and BIN_LIT cannot be used with FLOAT32_SUFFIX in Nim.

  Therefore, the part of the pattern that doesn't work in Nim is HEX_LIT ''' FLOAT32_SUFFIX, OCT_LIT FLOAT32_SUFFIX, and BIN_LIT FLOAT32_SUFFIX. Only decimal format floating-point literals (FLOAT_LIT and DEC_LIT) can have a FLOAT32_SUFFIX in Nim.

  Here are the corresponding examples:

  This works in Nim

  let floatLit = 1.0'f32

  let decLit = 123'f32

  This doesn't work in Nim

  let hexLit = 0x1.0'f32 # Nim doesn't support floating-point literals in hexadecimal

  let octLit = 0o1.0'f32 # Nim doesn't support floating-point literals in octal format

  let binLit = 0b1.0'f32 # Nim doesn't support floating-point literals in binary format

  It is recommend that these issues be addressed so that Nim's functionality aligns with the official documentation.

  Best regards.

  Antonio F.S.

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• Yardanico (orginal) [2023-10-31T01:19:02+01:00] view original

  I'm sorry to be a bit rude, but was your post generated or at least edited with the help of ChatGPT? Your non-working examples do not make sense, because hex/oct/bin float literals are about representing the floating value in hex/oct/bin, not just using the prefix and then writing it in decimal like usual.

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• janAkali (orginal) [2023-10-31T02:33:56+01:00] view original

  Perhaps you are confused about what is a literal is. A hexadecimal literal, is a representation of a number in the hexadecimal (base 16) number system.

  For Example, (I'm gonna use integers, because floating point hexadecimal is too complex for this example):

  0x123 does not equal 123, it's actually 1*16^2 + 2*16^1 + 3*16^0 = 291

  You can use hex literals in your code to represent Decimal value 129 in Hex form '0x123', not the other way around: '0x123.0 != 123.0'.

  If you want to represent Decimal value in other bases you can use functions defined in 'std/strutils <https://nim-lang.org/docs/strutils.html>'_: toBin(), toHex(), toOct()...'

  let decimalFloat = 123.56
  let hexString = cast[int](decimal).toHex(64) #cast is required, because toHex() accepts only the int Type
  Run

  Regarding ChatGPT or other AI tools: please, be aware they're very prone to hallucinate, even more so on niche topics like Nim programming language.

  Further Reading:

  • https://en.wikipedia.org/wiki/Hexadecimal
  • https://en.wikipedia.org/wiki/Type_conversion (casting)
  • https://www.exploringbinary.com/hexadecimal-floating-point-constants/

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• Araq (orginal) [2023-10-31T08:20:05+01:00] view original

  The intention here is to allow 0xaaa'f32 which is a float32 number of the bit pattern 0xaaa. It's possible and that both the grammar and the implementation are wrong but it suffices to use the issue tracker for it as there is no controversial design aspect here. I hope.

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• AntonioFS (orginal) [2023-10-31T09:47:39+01:00] view original

  Hello.

  My intention was not to judge anyone, I am simply learning Nim and together with PHIND, I am confirming with my checks in the IDE VS Code that what is in the manual, corresponds to the execution of the sentences.

  I use IA because it is very difficult for a novice to decipher without examples, according to what contents of the Nim manual.

  I posted the answer thinking that there was a manual error, but seeing that this is not the case, I will rely less on the AI and I will post my doubts here more often.

  Apologies and thanks. Antonio F.S.

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• AntonioFS (orginal) [2023-10-31T09:56:01+01:00] view original

  Thank you Yardanico and janAkali for your explanations but above all, for the examples (in Spain we say that a picture is worth a thousand words :-) ). Now I understand better.

  Thank you Araq too, for your explanation.

  Best regards. Antonio F.S.

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