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### Re: Map coordinates?

by roboticus (Chancellor)
 on Sep 02, 2019 at 18:21 UTC Need Help??

When you get some incomprehensible code, I'd suggest first running it through perltidy to get a better feel for what it looks like. You can then put in a few print statements to see what the values are initialized to. When I did so, I got this:

```\$ perltidy pm_11105453.pl
\$ vi pm_11105453.pl
<<< I then used vi to add some print statements to the result >>>
\$ cat pm_11105453.pl.tdy
@t    = map { \$_ * ( \$_ + ( \$_ - 1 ) ) % 4 } ( 2, 3, 4 );

print "T=(", join(", ", @t), ")\n";     # What do we have in @t?

\$i    = chr(0x34);
\$five = chr(55);

print "I=\$i, FIVE=\$five\n";             # What's in \$i and \$five?

print "\$i\$five "
. ( @t + @t )
. ( \$i / 2 ) . "."
. @t
. chr(0x35)
. ( @t * 3 + 1 ) . "\n";
@x = map { ( srand(1) * \$_ ) % 9 } ( 28, 34, 57 );

print "X=(", join(", ", @x), ")\n";     # What do we have in @x?

print @x
. ( @x * 2 )
. ( @x * 2 * 2 / 2 ) . " "
. chr(48)
. ( @x * 3 ) . "."
. ( @x + 1 )
. chr(0x30)
. ( ( @x % 4 ) - 3 ) . "\n";

\$ perl pm_11105453.pl.tdy
T=(2, 3, 0)
I=4, FIVE=7
47 52.257
X=(1, 7, 3)
122 09.400

After we run the code, we can see that it sets @t to (2, 3, 0) and @x to (1, 7, 3). If you had real code (instead of this obfuscated nonsense), you could analyze the functions map is applying to the incoming lists for initializing the @t and @x variables. I'd just edit the code and set @t and @x with the final values.

After cleaning up the variable initializations, I'd then start looking for ways to simplify the various bits of code.

For example, \$i and \$five are nearly unused--\$five is used only once in a print statement, \$i is used once in an expression and once in a print statement. So I'd delete those two variables and replace their uses with the corresponding values (4 for \$i and 7 for \$five). Variable deletion isn't always something I suggest, but sometimes it's the right tool.

Next, I'd take advantage of any obvious algebraic simplifications, such as ( 4 / 2 ) with 2 and ( @x * 2 * 2 / 2 ) with ( @x * 2 ) and also replace constant function calls (such as the ones to chr()) with the results.

Note: You can do a quick command-line experiment to find out the values from constant function calls, like this:

```\$ perl -e 'print chr(0x35)'
5
\$ perl -e 'print chr(0x30)'
0
\$ perl -e 'print chr(48)'
0

After doing this, and removing the now unnecessary print statements, I got:

```@t = (2, 3, 0);
@x = (1, 7, 3);

print "47 "
. ( @t + @t )
. 2 . "."
. @t
. '5'
. ( @t * 3 + 1 ) . "\n";

print @x
. ( @x * 2 )
. ( @x * 2 ) . " "
. '0'
. ( @x * 3 ) . "."
. ( @x + 1 )
. '0'
. ( ( @x % 4 ) - 3 ) . "\n";

From here, you could even replace all the references to @t and @x with their values, simplify further and boil the code down to:

```print "47 52.257\n";
print "122 09.400\n";

...roboticus

When your only tool is a hammer, all problems look like your thumb.

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