Scan padding and length specifiers properly

[Happypig375]

Description

%02d, %5.2f, % i

Repro steps

#r "nuget:FSharpPlus"
FSharpPlus.Parsing.trySscanf "%02d" "13"
FSharpPlus.Parsing.trySscanf "%5.2f" "313.2"
FSharpPlus.Parsing.trySscanf "% i" "13"

Expected behavior

Some 13
Some 313.2
Some 13

Actual behavior

None
None
None

Known workarounds

No

Related information

• Operating system: Windows
• Version: 1.1.7
• .NET Runtime, CoreCLR or Mono Version: F# Interactive version 11.4.2.0 for F# 5.0

[gusty]

Thanks for reporting it.
I am aware of this limitation. This is something that requires some work and proper testing.
Let's keep the issue open, in the meantime a PR is more than welcome.