Posted on Mon 08 June 2020

### why perl is the best language

Perl is the best language if it’s the language that you remember well enough.

My father loves math puzzles. He told me about one he was working on, and I did a quick estimate of how complex the answer space was and told him that it would be faster to have a computer try out every answer than to be clever about solving it.

Of course he wanted me to prove that, so I had to brush off Perl or Python. For some reason, Perl felt better.

The puzzle: assign the numbers 1 through 9 to letters without repetition or omission in order to solve the following equations:

1. AB x C = DE
2. DE + FG = HI
``````
for (my \$A=1; \$A <= 9; \$A++) {
for (my \$B=1; \$B <= 9; \$B++) {
next if \$A == \$B;
for (my \$C=1; \$C <= 9; \$C++) {
next if \$B == \$C;
next if \$A == \$C;
for (my \$D=1; \$D <= 9; \$D++) {
next if \$C == \$D;
next if \$B == \$D;
next if \$A == \$D;
for (my \$E=1; \$E <= 9; \$E++) {
next if \$D == \$E;
next if \$C == \$E;
next if \$B == \$E;
next if \$A == \$E;
for (my \$F=1; \$F <= 9; \$F++) {
next if \$E == \$F;
next if \$D == \$F;
next if \$C == \$F;
next if \$B == \$F;
next if \$A == \$F;
for (my \$G=1; \$G <= 9; \$G++) {
next if \$F == \$G;
next if \$E == \$G;
next if \$D == \$G;
next if \$C == \$G;
next if \$B == \$G;
next if \$A == \$G;
for (my \$H=1; \$H <= 9; \$H++) {
next if \$G == \$H;
next if \$F == \$H;
next if \$E == \$H;
next if \$D == \$H;
next if \$C == \$H;
next if \$B == \$H;
next if \$A == \$H;
for (my \$I=1; \$I <= 9; \$I++) {
next if \$H == \$I;
next if \$G == \$I;
next if \$F == \$I;
next if \$E == \$I;
next if \$D == \$I;
next if \$C == \$I;
next if \$B == \$I;
next if \$A == \$I;
if (((10 * \$A + \$B )  * \$C)  == (( 10* \$D)  + \$E)) {
if ((10 * \$D + \$E) + (10 * \$F ) + \$G == (( 10 * \$H ) + \$I )) {
print \$A.\$B."x".\$C."=".\$D.\$E."  ".\$D.\$E."+".\$F.\$G."=".\$H.\$I."\n";
}
}
}}}}}}}}};``````