[flang] DECIMAL edit specifiers do not handle the value separator correctly in list-directed I/O.

[DanielCChen]

Consider the following code:

      implicit none

      real :: rlarr(5) = (/1.11,22.2,333.33,44.4,0.0/)
      character(170) :: buffer_comma(3)
      character(170) :: buffer_point(3)

      namelist /nml_r/ rlarr

      write(buffer_comma,nml_r,decimal='comma')
      write(6,*) buffer_comma

      write(buffer_point,nml_r,decimal='point')
      write(6,*) buffer_point
      end

Flang prints

  &NML_R RLARR= 1,11 22,2 333,33 44,4 0,/

  &NML_R RLARR= 1.11 22.2 333.33 44.4 0./

While the test case is expecting

  &NML_R RLARR= 1,11; 22,2; 333,33; 44,4; 0,/

  &NML_R RLARR= 1.11, 22.2, 333.33, 44.4, 0./

The standard says [24-007: 13.6]

If the decimal edit mode is COMMA during list-directed input/output, the character used as a value separator is a semicolon in place of a comma.

It seems the value separator is missing from both decimal edit modes.

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` implicit none

  real :: rlarr(5) = (/1.11,22.2,333.33,44.4,0.0/)
  character(170) :: buffer_comma(3)
  character(170) :: buffer_point(3)

  namelist /nml_r/ rlarr

  write(buffer_comma,nml_r,decimal='comma')
  write(6,*) buffer_comma

  write(buffer_point,nml_r,decimal='point')
  write(6,*) buffer_point
  end

Flang prints 

&NML_R RLARR= 1,11 22,2 333,33 44,4 0,/

&NML_R RLARR= 1.11 22.2 333.33 44.4 0./

While the test case is expecting

&NML_R RLARR= 1,11; 22,2; 333,33; 44,4; 0,/

&NML_R RLARR= 1.11, 22.2, 333.33, 44.4, 0./

The standard says [24-007: 13.6]

If the decimal edit mode is COMMA during list-directed input/output, the character used as a value separator is a semicolon in place of a comma.

It seems the `value separator` is missing from both decimal edit modes.
</details>

[eugeneepshteyn]

13.11.4.1 states: "...the values are separated by one or more blanks or by a comma, or a semicolon if the decimal edit mode is
COMMA...". I understand this to mean that blank is a valid separator, even in the COMMA mode. (If separator happens to be a comma, then it should change to semicolon in COMMA mode.) Essentially, semicolon is an escape character for a comma, in case comma is used.

The flang output in POINT mode is &NML_R RLARR= 1.11 22.2 333.33 44.4 0./, the commas are not used. The output in COMMA mode is &NML_R RLARR= 1,11 22,2 333,33 44,4 0,/. Since comma separators are not used, there's nothing to escape, so there's no need for semicolon.

The test case uses commas to separate the values, so in COMMA mode escaping is necessary.

[klausler]

For namelist output, I just use single spaces as separators. For namelist input, the DECIMAL= control is relevant, and determines whether a comma is interpreted as a separator or part of a real number.