Execute HQ9+: Difference between revisions

Line 825:

This is F77 style except for the END SUBROUTINE HQ9, since F90+ allows the END statement to name its subroutine, and more seriously, the SELECT CASE construction that avoids interminable IF ... THEN ... ELSE IF ... sequences or even, a computed GO TO. The obvious data structure is the CHARACTER type, introduced with F77.

The only difficulty lies in the phasing of the various components of the recital, and especially, producing correct grammar for the singular case. One could simply produce *"1 bottles of beer", or perhaps "1 bottle(s) of beer" but having been hounded for decades by compilers quibbling over syntax trivia, a certain sensitivity has arisen. For this case, the requirement is to append a "s" or not to "bottle" and the task is quite vexing because Fortran does not allow within expressions syntax such as <lang Fortran>"bottle" // IF B.NE.1 THEN "s" FI // " of beer"</lang> so alternative schemes must be devised.

The only difficulty lies in the phasing of the various components of the recital (note the lines ending with commas or periods), and especially, producing correct grammar for the singular case. One could simply produce the likes of *"1 bottles of beer", or perhaps "1 bottle(s) of beer" but having been hounded for decades by compilers quibbling over syntax trivia, a certain sensitivity has arisen. For this case, the requirement is to append a "s" or not to "bottle" and the task is quite vexing because Fortran does not allow within expressions syntax such as <lang Fortran>"bottle" // IF (B.NE.1) THEN "s" FI // " of beer"</lang> so alternative schemes must be devised. There are many possibilities. The output line could be written piecemeal using the "non-advancing" options introduced in F90 with the "s" being written or not, or, the output line could be developed piecemeal in a CHARACTER variable in a similar way then written in one go. Alternatively, a character variable SUFFIX could be employed, which contains either "s" or " " with its usage being <code>..."bottle"//SUFFIX(1:LSTNB(SUFFIX))//...</code> where function LSTNB fingers the last non-blank character (if function TRIM or LEN_TRIM are unavailable), or, with F2003 there is a facility whereby SUFFIX can be declared with a varying length so as to be either "s" or "". Still another ploy would be to replace the "s" by a "null" character (character code zero) that will be passed over by the device showing the output. Or maybe not...

However, because the tail end of the recital does not conform to the structure of the earlier verses, it seemed easier to combine the singular case with the coda, especially since "No bottles" is to be produced instead of "0 bottles". It would be easy enough to devise a function CARDINAL(N) that would return "Ninety-nine", ... "One", "No" but the required code would swamp the rest of the project.

So, there is a careful factorisation of the text phrases into FORMAT and WRITE statements. Note that "free-format" output (as with <code>WRITE (6,*)</code> starts in the second column, whereas formatted output starts in the first column.