stdlib_io: add `print_array` function to print arrays to output units #981

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zoziha wants to merge 4 commits into fortran-lang:master

from zoziha:print_array-1

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stdlib_io: add `print_array` function to print arrays to output units #981

zoziha wants to merge 4 commits into fortran-lang:master from zoziha:print_array-1

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@zoziha zoziha commented Apr 20, 2025

Description

Add print_array subroutine, which is used to print two-dimensional arrays of integer and floating-point types. These two types are more commonly used in Fortran. It supports arguments such as delimiter, output unit, output format, and whether to print briefly.

In the non-brief output mode, the print_array function can produce an output result style similar to that of savetxt in stdlib_io. The print_array function is mainly convenient for users to output to the screen (standard output) and is likely to be mostly used for code debugging.

Prior Art:

disp in Matlab;
The default print of Python and Julia;
brief_print in Armadillo.

This PR will replace #520, and is related to #40, but is not sufficient to close #40.

Remaining to be discussed

Is it necessary to support delimiters of any length, not just those with a length of 1? In addition to the print_array, it also includes the savetxt routine in stdlib_io.
Currently, print_array is designed to assist users in program debugging and does not provide file write error reports like savetxt does.

zoziha added 2 commits

April 20, 2025 19:23

@zoziha


 feat(stdlib_io): add print_array subroutine to print 2D arrays to out...

a201a12

...put units

@zoziha


 fix(test): fix for ifx

036e759

@zoziha zoziha requested a review from Copilot

April 20, 2025 12:37

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Pull Request Overview

This pull request adds a new subroutine specification, print_array, to the stdlib_io module for printing 2D arrays to an output unit.

Introduces detailed documentation covering the subroutine’s syntax, argument descriptions, and an example.
Specifies default behaviors for output unit, delimiter, format, and brief mode.

Files not reviewed (7)

example/io/CMakeLists.txt: Language not supported
example/io/example_print_array.f90: Language not supported
src/CMakeLists.txt: Language not supported
src/stdlib_io.fypp: Language not supported
src/stdlib_io_print_array.fypp: Language not supported
test/io/CMakeLists.txt: Language not supported
test/io/test_print_array.f90: Language not supported

This was referenced Apr 20, 2025

[stdlib_io] add disp(display variable values formatted). #520

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stdlib_system: add get_terminal_size subroutine #983

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Apr 23, 2025

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Thank you @zoziha . Here are some minor comments.

doc/specs/stdlib_io.md Outdated Show resolved Hide resolved

doc/specs/stdlib_io.md Outdated

`delimiter`: Shall be a character string of length 1 containing the delimiter between array elements. It is an `intent(in)` argument. The default is a `" "` (space).

`brief`: Shall be a logical flag. If `.true.`, the array is printed in a brief format. The default is `.true.`.

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what is a "brief" format? Could you maybe provide a short definition?

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@zoziha zoziha Apr 25, 2025

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Okay. Details of the "brief" format were added, and an example was deliberately provided to illustrate the usage of the "brief" format.

doc/specs/stdlib_io.md

{!example/io/example_get_file.f90!}

```

## `print_array` - Print an array to an output unit

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Minor comment: the name could be discussed with the community. Personally, I would prefer disp.

src/stdlib_io_print_array.fypp Outdated Show resolved Hide resolved

@zoziha


 stdlib_io: update print_array and its docs

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@zoziha zoziha force-pushed the print_array-1 branch from db028c5 to 7c7b8b8 Compare

April 25, 2025 08:44

@zoziha


 docs(stdlib_io): Add an example to show the brief mode of print_array

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@Mahmood-Sinan

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Mahmood-Sinan commented Oct 13, 2025

Hi,
I noticed that complex arrays are printed as separate real and imaginary parts, rather than (a,b) or a + bi.

complex, dimension(2, 2) :: a = reshape([cmplx(1,2), cmplx(3,4), cmplx(5,6), cmplx(7,8)], [2,2])
print *, a
print "(a)", "=== print_array 1 ==="
call print_array(a, unit=6, fmt='(f7.1)', delimiter='|', brief=.false.)

The above code displayed

 (1.00000000,2.00000000) (3.00000000,4.00000000) (5.00000000,6.00000000) (7.00000000,8.00000000)
=== print_array 1 ===
 1.0| 2.0| 5.0| 6.0
 3.0| 4.0| 7.0| 8.0

For readability, it might be nicer to display them as in brackets or in a+bi form. One idea could be to add an optional complex_format flag (or similar) that controls whether complex numbers are printed as (a,b) or a + bi.

Mahmood-Sinan

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Oct 20, 2025

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Thank you @zoziha. One suggestion:
Can each entry of complex type array be printed as (a,b) form instead of using a delimiter between the real and imaginary parts. For example, for an array
complex, dimension(2, 2) :: a = reshape([cmplx(1,2), cmplx(3,4), cmplx(5,6), cmplx(7,8)], [2,2])
can the output be displayed as:

(1.0,2.0) | (5.0,6.0)
(3.0,4.0) | (7.0,8.0)

instead of

 1.0| 2.0| 5.0| 6.0
 3.0| 4.0| 7.0| 8.0

where delimiter is |.

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@zoziha zoziha commented Apr 20, 2025

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Mahmood-Sinan commented Oct 13, 2025

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stdlib_io: add `print_array` function to print arrays to output units #981

stdlib_io: add `print_array` function to print arrays to output units #981

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