Savetxt unit

[fiolj]

This PR aims to add optional arguments to savetxt, that behave similar to numpy's savetxt.

This is associated with Issue 263 and this discussion thread.

It add the possibility of supplying the unit of an open file instead of a filename (which could be used for output_unit for instance)

This implementation is quite simple. The main changes are:

1. Add optional header and footer (that could be commented out with a character, currently defaults to '#')
2. Changes delimiter to an arbitrary length string. I am not completely sure that is really useful. Initially I've added this because np.savetxt (Numpy's) allows character or arbitrary strings but np.loadtxt requires it to be a length 1 char.
3. Add the possibility to override default format for saving data

[codecov]

Codecov Report

❌ Patch coverage is 83.95062% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.80%. Comparing base (fb63d7e) to head (03cd77c).
⚠️ Report is 27 commits behind head on master.

Files with missing lines	Patch %	Lines
example/io/example_savetxt.f90	0.00%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1085      +/-   ##
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+ Coverage   68.00%   68.80%   +0.79%     
==========================================
  Files         404      407       +3     
  Lines       12935    13690     +755     
  Branches     1392     1543     +151     
==========================================
+ Hits         8797     9419     +622     
- Misses       4138     4271     +133     

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[jalvesz]

Thanks for this @fiolj. Would you mind reverting the changes not related to the implementation? (styling) There are too many and it renders difficult to read through the PR. You can check the style_guide for info https://github.com/fortran-lang/stdlib/blob/master/STYLE_GUIDE.md

One thing, white spaces in-between parentheses and an intrinsic function are not recommended ( open (...), allocate (...), etc )

[fiolj]

Thanks @jalvesz, I've fixed the formatting

[jvdp1]

Thank you @fiolj . Here are some suggestions

[fiolj]

Reviewing the arguments of savetxt I've rechecked and Numpy's has the following order:
np.savetxt(fname, X, fmt, delimiter, newline, header, footer, comments, encoding)

Currently, we have the order of fmt and delimiter inverted. Should we make it as Numpy or should we keep it?

[jvdp1]

LGTM. Thank you @fiolj

[fiolj]

In my opinion it has converged, I would be happy to make changes if necessary. Could we get a new review and try to complete the task and merge this PR?

[jvdp1]

Thank you @fiolj . Overall LGTM. There are still a few open comments/suggestions. Could you review them and implement/close them, please?

[jvdp1]

@fiolj Is this a valid suggestion?

[fiolj]

Thanks @jvdp1 for the review.
With regard to this comment, I do not understand well the question.

• I've simplified the error handling when something happens at reading the values (message formatted with format 1) by using a string variable fout.
• I've now also added a call to error_stop() when unit is not open (line 332).
• Also I've cleaned-up some comments

[fiolj]

I've updated the specs to clarify the behavior when the file already exists (as suggested in the discussion thread):

• When used with filename as a first argument it will overwrite the file
• When used with unit as first argument it will append data

[fiolj]

I've updated the specs to clarify the behavior when the file already exists (as suggested in the discussion thread):

* When used with `filename` as a first argument it will overwrite the file

* When used with `unit` as first argument it will append data

I've been thinking on the suggestion on the the discussion thread) about consistency of the arguments. The use of an additional argument append would give a consistent behavior.
The spec would change to something like:

---

Syntax

call savetxt(filename, array [, delimiter] [, fmt] [, header] [, footer] [, comments] [, append])

call savetxt(unit, array[, delimiter] [, fmt] [, header] [, footer] [, comments] [, append])

Arguments

...

append (optional): Shall be a logical flag. If .true. data will be appended at the end of the file or unit. If .false. file will be overwritten. Default: .false.

---

The only problem that I can see is that when used with an unit number, the function will always be modifying the position of the file (to the beginning or the end). In the previous version the user could in principle position it arbitrarily.

Thoughts, preferences?

[fiolj]

Hi, I've reverted some of the changes, to the previous version, removing the append option for filenames.
Also, added some checks to the file and unit (open, writable)
I think that there are not previous open comments or suggestions pending. If contributors agree, I'd like it to be merged

[jalvesz]

LGTM @fiolj! modulo some cosmetic suggestions I think this is ready to be merged.