SML/NJ implementation of `Date.fromTimeLocal` differs from SML Basis Library Documentation

[Skyb0rg007]

Version

110.99.4 (Latest)

Operating System

• Any
• Linux
• macOS
• Windows
• Other Unix

OS Version

No response

Processor

• Any
• Arm (using Rosetta)
• PowerPC
• Sparc
• x86 (32-bit)
• x86-64 (64-bit)
• Other

System Component

Basis Library

Severity

Minor

Description

In the SML Basis Library, Date.fromTimeLocal has the following document string (emphasis mine):

fromTimeLocal t
fromTimeUniv t
These convert the (UTC) time t into a corresponding date. fromTimeLocal represents the date in the local time zone; it is the analogue of the ISO C function localtime. The returned date will have offset=NONE. fromTimeUniv returns the date in the UTC time zone; it is the analogue of the ISO C function gmtime. The returned date will have offset=SOME(0).

This is not how the function is implemented in SML/NJ:

fun fromTimeLocal t = let
  val offset = localOffsetForTime (timeToNs t)
  in
    tm2date (localTime t, SOME offset)
  end

fun tm2date (tm, offset) = DATE{
    (* ... *)
    offset = offset,
    (* ... *)
    }

Transcript

- Date.offset (Date.fromTimeLocal (Time.now ()));
val it = SOME (TIME {usec=18000000000}) : time option

Expected Behavior

- Date.offset (Date.fromTimeLocal (Time.now ()));
val it = NONE : time option

Steps to Reproduce

See transcript

Additional Information

This isn't a big deal, but incompatibilities should be documented, especially since the SML/NJ documentation page simply links to smlfamily.github.io.

Email address

skyler.soss@gmail.com

[JohnReppy]

Fixed for 110.99.5