Chebyshev coefficients: Difference between revisions

<lang perl6>sub chebft ( Code $func, Real $\a, Real $\b, Int $\n ) {

my $\bma = 0.5½ *× ( $b - $a );

my $\bpa = 0.5½ *× ( $b + $a );

my @pi_npi-n = ( (^$n).list »+» 0.5½ ) »*×» ( pi π/ $n );

my @f = ( @pi_n».cos »*×» $bma »+» $bpa )».&$func;

my @sums = (^n).map: { [+] @f »*׫ ( @pi_npi-n »*×» $_ )».cos }, ^$n;

return @sums »*×» ( 2 / $n );

say .fmtchebft('%+13.7e') for chebft &cos, 0, 1, 10)».fmt: '%+13.7e';</lang>

<pre>+1.6471695e+00

-1.0021994e-11</pre>