Vintage Fortran

VIntage Fortran (VIF) is my experimental compiler for much vintage Fortran source code. VIF does not emulate the Fortran machine model as do other compilers using C as an intermediate language. VIF cannot compile little-used archaic statements that have no straightforward C equivalent. This is a trade-off between completeness and object code efficiency. Furthermore, VIF has reserved words and spaces in statements are significant, unlike old Fortran. Despite these restrictions, VIF compiles most vintage code. I like to think that at the time, programmers were already keen on coding in a legible and portable way, avoiding Fortran's idiosyncrasies.

In case you need to compile code with statements that have no C equivalent, specifically ENTRY, alternate RETURN, or some EQUIVALENCE statements, you will want to use production-quality FOSS solutions like f2c or GNU fortran. Here you can download the current VIF source distribution.

A goal for VIF was to make available high precision data types REAL*32 and COMPLEX*64, considering that most multi-precision applications require twenty up to sixty digits. VIF is probably the only vintage Fortran implementation offering these types.

A caveat when compiling vintage code is that in the old days, different machines had different representations of types, which are not always compatible with the IEEE standard common today. For instance, a REAL value occupied a 64-bit word in CRAY-1 FORTRAN, a 36-bit word in PDP-10 FORTRAN and a 32-bit word in IBM FORTRAN. Portable programs from the time refer to routines like D1MACH to inquire for limits of a type representation. For example, next trivial code snippet x1mach.f prints machine parameters for REAL*32 analogous to the D1MACH function:

      real*32 x1mach
      do k = 1, 5
      print *, k, x1mach(k)
      end do
      end

VIF can immediately execute a program upon successful compilation, like WATFOR or WATFIV, or a JCL CLG-type procedure under MVS or z/OS. We can execute above snippet with VIF like so, specifying -g:

$ vif -g x1mach.f
** main       ** end of compilation 1
** linker     ** object size 372280 bytes
** statistics ** 1 subprogram, no errors, no warnings
** execution  **
1  3.3621031431120935062626778173217526025980793448464712401088272298088533e-4932
2  1.1897314953572317650857593266280071307634446870965102374726748212332616e+4932
3  1.1319598848533390459386399113609739725853163997673922736978268612419382e-0072
4  2.2639197697066780918772798227219479451706327995347845473956537224838764e-0072
5  3.0102999566398119521373889472449302676818988146210854131042746112710819e-0001

Below is a list with the cross-referenced source files of the current version. VIF builds a library with (selected) FOSS subprograms from BLAS, LINPACK, SLATEC etcetera. These FOSS vintage library subprograms are not indexed here.

VIF C source files

	File	Synopsis	Lines
1	assign.c	Compile assignment statements.	180
2	autosave.c	Compile storage classes, SAVE statement.	181
3	banner.c	Banner for listing files.	169
4	call.c	Compile subprogram calls.	167
5	code.c	Routines to emit C object code.	468
6	common.c	Compiler COMMON statements.	146
7	data.c	Compile DATA statements.	336
8	decls.c	Compile declarations.	309
9	diag.c	Diagnostic routines.	100
10	dimension.c	Compile DIMENSION statements.	119
11	emit.c	Emit C object code.	205
12	equivalence.c	Compile EQUIVALENCE statements.	233
13	expr.c	Compile Fortran expressions.	603
14	factor.c	Compile Fortran expression factors.	315
15	fold.c	Constant folder.	558
16	format.c	Compile FORMAT statements.	438
17	fpp.c	Fortran preprocessor.	155
18	goto.c	Compile GOTO statements.	137
19	implicit.c	Implicit declaration routines.	185
20	intrinsic.c	Compile intrinsic functions.	630
21	macro.c	Compile function statements.	179
22	modules.c	Compile BLOCK DATA, FUNCTION, PROGRAM and SUBROUTINE.	602
23	parameter.c	Compile PARAMETER statement.	75
24	renum.c	Vintage Fortran statement renumbering tool.	574
25	rts.c	Runtime support.	295
26	rts-io.c	Runtime support for Fortran IO.	989
27	rts-jit.c	Just-in-time compilation of FORMAT strings.	390
28	rts-lapack.c	Runtime support for LAPACK subprograms.	805
29	rts-math.c	Runtime support for math operations.	468
30	rts-real16.c	Runtime support for REAL16 and COMPLEX32.	132
31	rts-real32.c	Runtime support for REAL32 and COMPLEX64.	2436
32	rts-slatec.c	Runtime support for SLATEC subprograms.	384
33	rts-wapr.c	Runtime support implementing the W-function.	359
34	scan.c	Fortran scanner.	693
35	slice.c	Compile array slices.	203
36	statements.c	Compile statements.	652
37	table.c	Symbol table routines.	310
38	transput.c	Compile Fortran IO.	954
39	type.c	Type routines.	342
40	vif.c	VIF driver.	662

VIF Fortran source files

	File	Synopsis	Lines
1	fortran-ii.f	FORTRAN II library functions for VIF.	44
2	fortran-iv.f	FORTRAN IV intrinsic library functions for VIF.	450
3	ml.f	Machine Learning subprograms for VIF.	210