1. Tip march 10
To designate valid values that you might change instead of
coding each value directly to the if statements like
if c = '8' then--use for up
elsif c = '2' then--use for down
elsif c = '4' then--use for left
elsif c = '6' then --use for right
end if
set a sequence with valid values and search them
integer found
sequence s
s = "8246"
found = find(c, s)
--this will also speed the checking by making sure it
--was valid/found first.
if found then
--found tells where c was found.
if found = 1 then--use for up
elsif found = 2 then--use for down
elsif found = 3 then--use for left
elsif found = 4 then --use for right
end if
end if
--Lucius Lamar Hilley III
-- E-mail at luciuslhilleyiii at juno.com
-- I support transfering of files less than 64K.
-- I can Decode both UU and Base64 format.
2. Re: Tip march 10
Lucius Lamar Hilley III writes:
> To designate valid values that you might change instead of
> coding each value directly to the if statements like
>
> if c = '8' then--use for up
> elsif c = '2' then--use for down
> elsif c = '4' then--use for left
> elsif c = '6' then --use for right
> end if
>
> SNIP
>
> found = find(c, s)
> --this will also speed the checking by making sure it
> --was valid/found first.
> if found then
> --found tells where c was found.
> if found = 1 then--use for up
> elsif found = 2 then--use for down
> elsif found = 3 then--use for left
> elsif found = 4 then --use for right
> end if
> end if
Um... you're kidding, right? It seems to me that replacing the hard coded
values (which at least have intrinsic meaning) with arbitrary index values
(which are therefore meaningless) is far less maintainable, and much more
prone to error.
You've simply replaced one type of hard-coded information (key codes) with
another (index position). If you added an item into that list of key codes
(other than at the tail), all your code *breaks*.
Wouldn't a more you want to use symbolic constants, such as:
validKeys = { UP, DOWN, LEFT, RIGHT }
if find( key, validKeys ) then
if key = UP then--use for up
elsif key = DOWN then--use for down
elsif key = LEFT then--use for left
elsif key = RIGHT then --use for right
end if
If the range is large, and there are a lot of items, you can do what Robert
does in the syntax coloring code: set up a sequence the size of the range,
and fill it with values. For example:
repeat validKeys( 0, 256 ) -- all values are initially false
validKeys[UP] = 1 -- up is valid
validKeys[DOWN] = 1 -- down is valid
validKeys[LEFT] = 1 -- left is valid
validKeys[RIGHT] = 1 -- right is valid
He also does a real neat trick, setting a full range:
validKeys['a'..'z'] = 1 -- 'a' through 'z' are valid
You can then use the value you are testing as an index into the sequence:
if validKeys[key] then
...
This technique becomes even more useful if you have values other than true
or false (for example, the syntax coloring code returns the class of the
character). Back when I was a FORTH coder, we used to build arrays and poke
them with jump addresses instead of using CASE statements. Given a value,
you would use it as an index, grab the address from the table, and jump. Of
course, you pray you never get an index that exceeds the table bounds...
Just a suggestion.
-- David Cuny
