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Chaoji Li > Algorithm-Step-0.02 > MyStep

# NAME

MyStep - Trace execution steps of an algorithm

# SYNOPSIS

```        use Algorithm::Step;
use integer;

algorithm "P", "Print table of 500 primes";
my @PRIME = ();

step 1, "Start table, PRIME[1] <- 2, PRIME[2] <- 3";
\$PRIME[1] = 2;
\$n = 3;
\$j = 1;
\$PRIME[++\$j] = \$n;

while (\$j < 500) {

step 2, "Advance n by 2";
\$n += 2;

step 3, "k <- 1";
\$k = 1;

do {

step 4, "Increase k";
++\$k;

step 5, "Divide n by PRIME[k]";
\$q = \$n / \$PRIME[\$k];
\$r = \$n % \$PRIME[\$k];

step 6, "Remainder zero?";
next if \$r == 0;

step 7, "PRIME[k] large?";
} while (\$q > \$PRIME[\$k]);

step 8, "n is prime";
\$PRIME[++\$j] = \$n;
}

step 9, "Print result";
print "FIRST FIVE HUNDRED PRIMES\n";

\$m = 1;
do {
for (0,50,100,150,200,250,300,350,400) {
print \$PRIME[\$_+\$m], "\t";
}
print \$PRIME[450+\$m], "\n";
\$m++;
} while (\$m <= 50);

end_algorithm "P";```

# DESCRIPTION

This is for observing the behavior of algorithms on some algorithm textbooks, such as `The Art of Computer Programming', `Introduction to Algorithms'. I write it only for fun. I have been thinking of how to embed documents in program in a helpful way.

The usage is well demonstrated by the example above.

algorithm

Begins an algorithm. It takes two arguments. The first one is the name of this algorithm, the second one is the short description.

end_algorithm

Ends an algorithm.

step

Increase count on this step by 1. It can be nested. A step can be divided into sub steps, like:

```        step 1, "desc";
step 1,1, "desc";
step 1,2, "desc";
step 2, "desc";```
statistics

Print the execution information. If no argument is give, print to stdout. If a filename is given, print to that file.

`        statistics("prime.stat");`

The output looks like:

```  STATISTICS

Algorithm P: Print table of 500 primes
STEP 1. Start table, PRIME[1] <- 2, PRIME[2] <- 3 .... [1]
STEP 2. Advance n by 2 ............................... [1784]
STEP 3. k <- 1 ....................................... [1784]
STEP 4. Increase k ................................... [9538]
STEP 5. Divide n by PRIME[k] ......................... [9538]
STEP 6. Remainder zero? .............................. [9538]
STEP 7. PRIME[k] large? .............................. [8252]
STEP 8. n is prime ................................... [498]
STEP 9. Print result ................................. [1]```

# TODO

Generate from comments. If a file `prime.pl' looks like:

```        ...

# algorithm P: Print first five hundred primes

# step 5: Divide n by PRIME[k]

# end algorithm P

...```

Parse the comments, insert codes, and generate a new `step_prime.pl';

# BUGS

Surely there are many. This is still pre-alpha.