stdtoGAP.txt

Perl script to convert from std format to GAP format

For information about the data base of lattices, see:
<a href="index.html"><B>Index File</B></a> and
<a href="abbrev.html"><B>Abbreviations</B></a>.

We suggest that you:
o download this file
o copy it to a new file called stdtoGAP.perl,
o delete everything up to and including the line "cut 1 here",
o delete the line "cut 2 here" and everything after it,
o then make the file executable.
o To use it, type (for example) stdtoGAP.perl E8.std >out
then read "out" into GAP.

------- cut 1 here -------
#!/usr/bin/perl
# stdtoGAP.perl   Perl script to make GAP readable
# version of gram matrix from standard library file
# Last modified Feb 03 1997

if ( $#ARGV != 0 ) { die "Useage: stdtoGAP.perl file.std >out      " }

# check file name ends in .std
if ( ! $ARGV[0] =~ /\.std$/) { die "filename doesn't end with .std!     "}

# check if file exists
if ( ! -f $ARGV[0] )  { die "$ARGV[0] does not exist!    " }

# open lattice file ($1)
open(LATTICE,$ARGV[0]);

# states:  0 = neutral, 1 means have just read "^%GRAM", 
# 2 means reading Gram matrix
$state = "0";

# set up empty list to hold Gram matrix
@gramlist = ();

# read all input lines
while (<LATTICE>) {
	chop;  # delete newline at end
	$_ =~ s/^  *//;   # delete leading blanks
	@line = split;   # break up into a list

	if ( $#line < 0 ) {next }   # skip if empty line

	if ($line[0] =~ /^%/) { $state = "0" }  #reset state to 0 if find %

	if ($line[0] =~ /^%GRAM$/) {    # look for line beginning %GRAM
		$state = "1";           # sets state to 1, getting ready
					# for reading dimensions on next line
		next;              }

	if ($state =~ "1") { $d1 = $line[0];    # state = 1,
						# so read dimensions of array
                             $d2 = $line[1];
			     $state = "2";      # and set state to 2
			     next;
                           }  

	if ($state =~ "2" && $line[0] !~ /^%/) {    # reading Gram matrix
		$t1 = $#line;    # get no of entries on the current line
# add then to gram matrix
		push( @gramlist, @line)        }
    
                  }

# print in GAP format, calling the gram matrix "m"

# print LHS
print("m := [\\\n");

### case 1, Gram matrix given in square form:

if ( $d1 == $d2 )   # square Gram matrix

{                   # start bracket 1
$at = 0;
# print row i (but not the last one)
for ($i = 0; $i < $d1 - 1; $i = $i + 1) {
# print element j (but not the last one)
print("[\\\n");
	for ($j = 0; $j < $d1 - 1; $j = $j + 1)   {
		print($gramlist[$at],",\\\n");
		$at = $at + 1;                    };
# print last elt in row
		print($gramlist[$at],"],\\\n");
		$at = $at + 1;                   
					}
# print last row
$i = $d1 - 1;
print("[\\\n");
# print element j (but not the last one)
	for ($j = 0; $j < $d1 - 1; $j = $j + 1)   {
		print($gramlist[$at],",\\\n");
		$at = $at + 1;                    };
# print last elt in row
		print($gramlist[$at],"]]):\n");
}                   # end bracket 1

else

### case 2 , Gram matrix given in triangular form

{                   # start bracket 2
# print row i 
for ($i = 0; $i < $d1 ; $i = $i + 1) {
print("[\\\n");
# print column j

# print elements j = 0 .. i
	for ($j = 0; $j <= $i ; $j = $j + 1)   {
		$at = $i * ($i + 1)/2 + $j;
		print($gramlist[$at],"\\\n"); 
# follow it by a comma unless at end of line
		if ($j < $d1 - 1 ) {print(",\\\n"); } else { print("]\\\n");}
					       };

# print elements j = i+1 .. $d1-1
	for ($j = $i + 1; $j < $d1 ; $j = $j + 1)   {
		$at = $j * ($j + 1)/2 + $i;
		print($gramlist[$at],"\\\n");    
# follow it by a comma unless at end of line
		if ($j < $d1 - 1 ) {print(",\\\n"); } else { print("]\\\n");}
						    };
# print closing comma
	if ( $i < $d1 - 1 ) { print(",\\\n"); } else { print("]):\n"); }

				    };

}                    # end bracket 2


---------- cut 2 here -------