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digitalmars.D.learn - Array of Associative arrays

reply jicman <jicman_member pathlink.com> writes:
Greetings!

Please help me understand this one:

import std.stdio;
import std.string;
char[][char[]] ProcessUserLoginEntry(char[][char[]] ul,char[] line)
{
char[][] MyS0 = std.string.split(line," >>> Login: User ");
char[][] MyS1 = std.string.split(MyS0[1]," logged in");
char[]   user = MyS1[0];
MyS1          = std.string.split(MyS0[0]," STATUS ");
ul[user].length = ul[user].length + 1;
ul[user][ul[user].length - 1] = MyS1[1];
return ul;
}
void main()
{
char[] s = "20020729154320 STATUS Jul 29, 2002 3:43:20 PM >>>"; 
s       ~= " Login: User blah logged in ";
char[][char[]] aa;
aa = ProcessUserLoginEntry(aa, s);
}

when I compile it, I get,

jic 15:33:58-> build AssArrays.d 
AssArrays.d(10): cannot implicitly convert expression (MyS1[1]) of type char[]
to char

well, MyS1 is an array of char[][], so MyS1[1] should be char[].  Right?

Any help would be greatly appreciate it.  I mean, I know how to go about doing
this another way, but this is the easiest for me.

thanks,

josé
Jul 27 2005
parent reply Chris Sauls <ibisbasenji gmail.com> writes:
jicman wrote:

 import std.stdio;
 import std.string;
 char[][char[]] ProcessUserLoginEntry(char[][char[]] ul,char[] line)
 {
 char[][] MyS0 = std.string.split(line," >>> Login: User ");
 char[][] MyS1 = std.string.split(MyS0[1]," logged in");
 char[]   user = MyS1[0];
 MyS1          = std.string.split(MyS0[0]," STATUS ");
 ul[user].length = ul[user].length + 1;
 ul[user][ul[user].length - 1] = MyS1[1];
 return ul;
 }
 void main()
 {
 char[] s = "20020729154320 STATUS Jul 29, 2002 3:43:20 PM >>>"; 
 s       ~= " Login: User blah logged in ";
 char[][char[]] aa;
 aa = ProcessUserLoginEntry(aa, s);
 }
 
 when I compile it, I get,
 
 jic 15:33:58-> build AssArrays.d 
 AssArrays.d(10): cannot implicitly convert expression (MyS1[1]) of type char[]
 to char



Not surprising.  Look at these two lines:
# char[][char[]] ProcessUserLoginEntry(char[][char[]] ul,char[] line)
# ul[user][ul[user].length - 1] = MyS1[1];

In the first one you declare 'ul' to be type 'char[][char[]]' or, reading
right-to-left as 
per D convention: an associative array, keyed to arrays of char, of arrays of
char.  Or, a 
map of strings to strings.  Then MyS1 is of t ype 'char[][]' or: an array of
arrays of 
char.  Or, an array of strings.

The problem: the expression 'ul[user][ul[user].length - 1]' evaluates to a
char.  Look at 
it this way (assume ul[user] == "fred", and MyS1 contains ["foo", "bar"]):
## (ul[user])[((ul[user]).length) - 1] = MyS1[1];
## (ul[user])[("fred".length) - 1] = MyS1[1];
## "fred"[("fred".length) - 1] = MyS1[1];
## "fred"[4 - 1] = MyS1[1];
## "fred"[3] = MyS1[1];
## 'd' = "bar";

Maybe the type you were wanting was 'char[][][char[]]' meaning: an associative
array, 
keyed to arrays of char, of arrays, of arrays of char.  Or, a map of strings to
arrays of 
strings.  Either that or I'm misunderstanding something.

-- Chris Sauls
Jul 27 2005
next sibling parent reply jicman <jicman_member pathlink.com> writes:
Yep.  You didn't misunderstand something.

thanks.

josé

Chris Sauls says...

jicman wrote:

 import std.stdio;
 import std.string;
 char[][char[]] ProcessUserLoginEntry(char[][char[]] ul,char[] line)
 {
 char[][] MyS0 = std.string.split(line," >>> Login: User ");
 char[][] MyS1 = std.string.split(MyS0[1]," logged in");
 char[]   user = MyS1[0];
 MyS1          = std.string.split(MyS0[0]," STATUS ");
 ul[user].length = ul[user].length + 1;
 ul[user][ul[user].length - 1] = MyS1[1];
 return ul;
 }
 void main()
 {
 char[] s = "20020729154320 STATUS Jul 29, 2002 3:43:20 PM >>>"; 
 s       ~= " Login: User blah logged in ";
 char[][char[]] aa;
 aa = ProcessUserLoginEntry(aa, s);
 }
 
 when I compile it, I get,
 
 jic 15:33:58-> build AssArrays.d 
 AssArrays.d(10): cannot implicitly convert expression (MyS1[1]) of type char[]
 to char



Not surprising.  Look at these two lines:
# char[][char[]] ProcessUserLoginEntry(char[][char[]] ul,char[] line)
# ul[user][ul[user].length - 1] = MyS1[1];

In the first one you declare 'ul' to be type 'char[][char[]]' or, reading
right-to-left as 
per D convention: an associative array, keyed to arrays of char, of arrays of
char.  Or, a 
map of strings to strings.  Then MyS1 is of t ype 'char[][]' or: an array of
arrays of 
char.  Or, an array of strings.

The problem: the expression 'ul[user][ul[user].length - 1]' evaluates to a
char.  Look at 
it this way (assume ul[user] == "fred", and MyS1 contains ["foo", "bar"]):
## (ul[user])[((ul[user]).length) - 1] = MyS1[1];
## (ul[user])[("fred".length) - 1] = MyS1[1];
## "fred"[("fred".length) - 1] = MyS1[1];
## "fred"[4 - 1] = MyS1[1];
## "fred"[3] = MyS1[1];
## 'd' = "bar";

Maybe the type you were wanting was 'char[][][char[]]' meaning: an associative
array, 
keyed to arrays of char, of arrays, of arrays of char.  Or, a map of strings to
arrays of 
strings.  Either that or I'm misunderstanding something.

-- Chris Sauls
Jul 27 2005
parent reply Chris Sauls <ibisbasenji gmail.com> writes:
jicman wrote:

 Yep.  You didn't misunderstand something.



Okay good... I just happened to have an inspired moment or I don't think I
would've seen 
it either.  Hooray for stepping through expressions.


 thanks.



Anytime.

-- Chris Sauls
Jul 27 2005
parent jicman <jicman_member pathlink.com> writes:
Chris Sauls says...

jicman wrote:

 Yep.  You didn't misunderstand something.



Okay good... I just happened to have an inspired moment or I don't think I
would've seen 
it either.  Hooray for stepping through expressions.



Thank God for inspired moments. :-)


 thanks.



Anytime.

-- Chris Sauls
Jul 27 2005
prev sibling parent reply novice2 <novice2_member pathlink.com> writes:
Maybe the type you were wanting was 'char[][][char[]]' meaning: an associative
array, 
keyed to arrays of char, of arrays, of arrays of char.  Or, a map of strings to
arrays of 
strings.  Either that or I'm misunderstanding something.



this is example, why some D programmers like this:

alias char[] string;
string[][string] a;  /*easy to understand*/
Jul 28 2005
parent Chris Sauls <ibisbasenji gmail.com> writes:
novice2 wrote:

Maybe the type you were wanting was 'char[][][char[]]' meaning: an associative
array, 
keyed to arrays of char, of arrays, of arrays of char.  Or, a map of strings to
arrays of 
strings.  Either that or I'm misunderstanding something.



 
 alias char[] string;
 string[][string] a;  /*easy to understand*/



I've done this in some programs myself.  I'm personally fond of:
# alias char[]  str8  ;
# alias wchar[] str16 ;
# alias dchar[] str32 ;

-- Chris Sauls
Jul 29 2005