Generator/Exponential: Difference between revisions

libco is a tiny library that adds ''cooperative multithreading'', also known as ''coroutines'', to the C language. Its <tt>co_switch(x)</tt> function pauses the current cothread and resumes the other cothread <tt>x</tt>.

This example provides <tt>next64()</tt> and <tt>yield64()</tt>, to generate 64-bit integers. <tt>next64()</tt> switches to a generator. Then the generator passes some 64-bit integer to <tt>yield64()</tt>, which switches to the first cothread, where <tt>next64()</tt> returns this 64-bit integer.

while (c < s)

c = next64(&f.cubes);

=={{header|Perl}}==

These generators are anonymous subroutines, which are closures.

<lang perl># gen_pow($m) creates and returns an anonymous subroutine that will

# generate and return the powers 0**m, 1**m, 2**m, ...

sub gen_pow {

my $m = shift;

my $e = 0;

return sub { return $e++ ** $m; };

}

# gen_filter($g1, $g2) generates everything returned from $g1 that

# is not also returned from $g2. Both $g1 and $g2 must be references

# to subroutines that generate numbers in increasing order. gen_filter

# creates and returns an anonymous subroutine.

sub gen_filter {

my($g1, $g2) = @_;

my $v1;

my $v2 = $g2->();

return sub {

for (;;) {

$v1 = $g1->();

$v2 = $g2->() while $v1 > $v2;

return $v1 unless $v1 == $v2;

}

};

}

# Create generators.

my $squares = gen_pow(2);

my $cubes = gen_pow(3);

my $squares_without_cubes = gen_filter($squares, $cubes);

# Drop 20 values.

$squares_without_cubes->() for (1..20);

# Print 10 values.

my @answer;

push @answer, $squares_without_cubes->() for (1..10);

print "[", join(", ", @answer), "]\n";</lang>

Output: <pre>[529, 576, 625, 676, 784, 841, 900, 961, 1024, 1089]</pre>

(c = cubes.next) until c >= s

(c = cubes.next) until c >= s