Hi everyone,
Probably my last question for the week :) -- can I get help in writing a
function, perhaps with some explanation for the approach?
I would like a function that checks a file's existence; if the file is
does not exist, I want to write out a message to the console and (in my
non-J/APL lingo) throw an error to stop all execution (i.e. "barf"). If
the file does exist, I would like to read in the contents and "return"
all the data.
My rationale is that the script I am maintaining has a bunch of fread
calls which throw domain errors if the file does exist, but I have no
clue what file is trying to be read since "domain error" refers to the
fact that the script is trying to concatenate a -1 return of fread with
a path.
Also, the "big" script has several scripts in a single file, including
the one that reads in all the data, but the J debugger gives the line
number *within a function* so I don't know which line that is within the
script (though I could maybe do a little bit of math ....)
Here is my feeble attempt at my desired function:
readfile =: 3 : 0
if. fexist y do.
out .= fread y
else.
('readfile: ', y, ' does not exist')
this_is_supposed_to_bomb .=
end.
out
)
But here is the result:
1!:43 '' NB. thanks for the pointer to vocab -> foreigns
c:\j504
readfile 'version_bin.txt' NB. I know this file exists
readfile 'version_bin.txt'
|control error: readfile
| readfile'version_bin.txt'
|[-0]
I hope I am not trying everybody's patience too extremely. I do swear I
try to figure these things out from the documentation, but as I said
earlier I am trying to get up to speed more quickly than allows me to
really deal with J/APL in depth. I can only hope that your collective
answers to my cookbook-ish questions will provide a resource for others
later.
Thanks!
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