Hi. I'm Ron Jeffries. I've been experimenting with J language with
advice from Tracy Harms, Raul Miller, Henry Rich, and Gilles
Kirouac. (Thanks to you all, and to anyone I've missed.)
Gilles, in particular, detected that I may have dived in too deep,
and suggested that I go back to J for C programmers and work through
that. I had started with it but didn't really find it tasty, but on
his advice I'm going again.
I noticed in an early example, the accounts one, this patch of C code:
while(3 == fscanf(fid,"%f%f%f",acctno,xactnday,xactnamt) {
for(acctx = 0;acct[acctx].ano != acctno;++acctx);
acct[nacct].weightbal +=
acct[nacct].currbal * (xactnday - acct[nacct].prevday);
acct[nacct].currbal += xactnamt;
acct[nacct].prevday = xactnday;
}
A similar patch appears at the end of the example.
I'm quite rusty on C but it appears to me that the for loop finds
the value of acctx such that we have the right account number acctno
... but that the subsequent code updates account number nacct,
which, as the incremented value of nacct after the input read loop,
is in fact an uninitialized account struct.
Am I missing something? If not, maybe the example in JfC needs
updating. If nothing else, this surely shows that J is not subject
to this kind of error, or at least not quite so easily.
I'm sure I'll be back with beginner J questions soon. Thanks!
Ron Jeffries
www.XProgramming.com
If not now, when? -- The Talmud
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