If an automated @FortranFunc channel were created, tweeting a description of an intrinsic function per day, with an image containing demonstration code, maybe some people would subscribe. It could loop over the functions and statements such READ and WRITE and repeat every year or so. When people tired of it they would unsubscribe, but hopefully there would be new Fortran programmers who find the service useful. @FortranTip was inspired by @SciPyTip, which has 132K followers and tweets such as
np.nanmin() returns the minimum of an array ignoring nan values.
I do not think the intrinsic documents as constructed here would often be too long, but tips like modulo versus mod (I always have to look them up or try them when not using all positive values, as MOD truncates towards zero and the other does a FLOOR, and the formulas result in
(as you mentioned) getting the sign of A when the signs differ, and the other the sign of B for the same case … but I think your Fortran Tips is a good forum for that (it is usually MODULO I want when it matters, but I always have this doubt till I try it ).
Quick summaries, maybe with a link to the intrinsics documentation would be nice; but what might be more interesting because it would often be new might be stdlib routines and descriptions of resources like on your list of Fortran resources? hopefully the intrinsics documents will cover the descriptions of the intrinsics well enough that it will be mostly tips about them that will be of interest, and Fortran Tips is covering that already; so I like the idea but I think the missing piece is advertising resources that are out there, although your list, the Fortran Wiki, and the fpm repository and lists on fortran-lang.org and other pages cover that more and more.
In C, the intrinsics are functions such as printf (although technically they are part of the standard library). Fortran classifies as statements READ, WRITE, OPEN, INQUIRE, ALLOCATE etc. INQUIRE has specifiers, but one can think of it as a subroutine with intent(in) and intent(out) arguments.
I think the intrinsic descriptions project should eventually cover the statements of the language. The coverage may have to be incomplete, since book chapters have been written about READ and WRITE.
Yes, I agree; but the intrinsics themselves seemed lacking good coverage and are more straight-forward. The function-like statements (READ, WRITE, ALLOCATE, STOP, …) that can be suitably described in something like a man-page format were partially covered and being worked on in the predecessor (fpm-man) and hopefully will be introduced; but a lot of material needs covered in a book or tutorial format that I didn’t envision being covered in this collection. I am picturing this as being more like a dictionary is to a language rather than a book; particularly since these are often glossed over in books that do provide in-depth discussions of programming topics. Hopefully some minibooks on those topics will emerge too. But definitely agree, many statements can be thought of as procedures or functions and should ultimately at least be syntactically covered here. I lot of them were WIPs, but did have a few started, but not included here yet
1423 data (7fortran) - [FORTRAN] DATA statement
1428 use (7fortran) - [FORTRAN] gives a program unit access to public entities in a module.
1429 include (7fortran) - [FORTRAN] including source text
1433 iso_c_binding (7fortran) - [FORTRAN] standard intrinsic module which defines named constants, types, and procedures for C interoperability
1434 iso_fortran_env (7fortran) - [FORTRAN] standard intrinsic module provides public entities related to the Fortran environment
1436 where (7fortran) - [FORTRAN:ASSIGNMENT] masked array assignment
1437 associate (7fortran) - [FORTRAN:EXECUTION CONTROL] associate construct (LICENSE:PD)
1438 block (7fortran) - [FORTRAN:EXECUTION CONTROL] construct (LICENSE:PD)
1439 case (7fortran) - [FORTRAN:EXECUTION CONTROL] select a block based on the value of an expression (a case)
1440 continue (7fortran) - [FORTRAN:EXECUTION CONTROL] construct (LICENSE:PD)
1441 cycle (7fortran) - [FORTRAN:EXECUTION CONTROL] construct (LICENSE:PD)
1442 do (7fortran) - [FORTRAN:EXECUTION CONTROL] construct (LICENSE:PD)
1443 endselect (7fortran) - [FORTRAN:EXECUTION CONTROL] select a block based on the value of an expression (a case)
1444 exit (7fortran) - [FORTRAN:EXECUTION CONTROL] statement (LICENSE:PD)
1445 if (7fortran) - [FORTRAN:EXECUTION CONTROL] selects a block based on a sequence of logical expressions.
1446 select (7fortran) - [FORTRAN:EXECUTION CONTROL] select a block based on the value of an expression (a case)
1447 select_type (7fortran) - [FORTRAN:EXECUTION_CONTROL] select_type
1449 inquire (7fortran) - [FORTRAN:FILE_INQUIRE] File inquiry statement
1450 backspace (7fortran) - [FORTRAN:FILE_POSITIONING] - backspace one record on specified I/O unit
1451 rewind (7fortran) - [FORTRAN:FILE_POSITIONING] rewind specified sequential access I/O unit
1452 format (7fortran) - [FORTRAN:INTRINSIC:I/O] Format statement
1453 common (7fortran) - [FORTRAN:INTRINSICS] specifies blocks of variables that can be accessed by any scoping unit in the program
1454 equivalence (7fortran) - [FORTRAN:INTRINSICS] used to specify the sharing of storage units by two or more objects in a storage unit
1455 flush (7fortran) - [FORTRAN:IO] flush I/O buffers of specified files
1456 open (7fortran) - [FORTRAN:IO] Initiates or modifies a connection between an external file and a specified unit.
1458 read (7fortran) - [FORTRAN:IO] read data
1459 wait (7fortran) - [FORTRAN:IO] statement performs a wait operation for specified pending asynchronous data transfer operations
1460 close (7fortran) - [FORTRAN:IO] terminate the connection of a specified unit to an external file.
1464 deallocate (7fortran) - [FORTRAN:STATEMENT] causes allocated variables and targets to be deallocated
1465 nullify (7fortran) - [FORTRAN:STATEMENT] causes pointers to be disassociated from a target
1466 return (7fortran) - [FORTRAN:STATEMENT] completes execution of the instance of the subprogram in which it appears
1467 stop (7fortran) - [FORTRAN:STATEMENT] initiates termination of execution
1468 implicit (7fortran) - [FORTRAN:STATEMENT] specify default type (if any) associated to a starting letter
1469 namelist (7fortran) - [FORTRAN:STATEMENT] specify a group of data to be referred to by a single name in data input/output
There is a minor problem with the description of exp(cx) when cx is of type complex. The expression uses cmplx(cos(im),sin(im)), which is always of default kind. The correct description should be something like cmplx(cos(im),sin(im),KIND(cx)). Of course, this is because the cmplx() instrinsic is screwed up due to backwards compatibility, and it does not work in the expected/obvious way.
The example is default kind, but I agree that because cmplx(), to be backwards compatible, always defaults to the default real kind (UGH) the kind should be specified. Ironically that is a “gotcha” topic on an old FAQ collection of mine and I recommend always specifying the KIND there, so I changed the example accordingly to match your suggestion. I need to find a free moment and I will check all the documentation for the same. the issues with REAL and CMPLX really beg creating new intrinsics; or maybe re-invigorating FLOAT and DBLE.
I suggest that they be included in a minimal way. For each compiler it would be nice to have a two-column list where the left column has the extension and the right column the standard near-equivalent. The extension would have a link to vendor documentation. For gfortran, two examples are
info node for gfortran gives Part II → Extensions → Extensions implemented in GNU Fortran
E.g. on Ubuntu 20.04, the package gfortran-10-doc shows the following items in that menu:
Old-style kind specifications::
Old-style variable initialization::
Extensions to namelist::
X format descriptor without count field::
Commas in FORMAT specifications::
Missing period in FORMAT specifications::
Default widths for F, G and I format descriptors::
It could be interesting to indicate in the Wikipedia pages of those functions that they are available in Fortran, with the standard version and a link toward the description of the intrinsic. For example, on the erf(x) page, we see at the bottom that it can be available in C in math.h:
Concerning erf(x) and erfc(x), I have done it in the French page.
).