cgen

#!/usr/bin/perl

use strict;
use v5.12;

use Getopt::Long;

my $i = 2;
my $fn = "fn";
my $pfix = "";
my $l = 0;
my $tab = " "x($i*4);

GetOptions("l" => \$l, "f=s" => \$fn, "i=i" => \$i, "p=s" => \$pfix) or die;

my $c = shift @ARGV;

if (!$l) {
    # record syntax applicative traversal
    my @vs = map { "$pfix$_" } @ARGV;
    say "${tab}f $c { .. } = h <\$> ", join ( " <*> ",map { "$fn $_" } @vs);
    say "$tab    where h ", join (" ", @vs), " = $c { .. }";
    exit 0;
}

my $a = shift @ARGV;

if ($a =~ /^[0-9]+$/) {
    $a = "m"x$a;
}

# direct args
my $nds = 0;
$nds++ while $a =~ s/^p//;

my $n = length $a;
my @ds = map { "d$_" } (1 .. $nds);
my @vs = map { "a$_" } (1 .. $n);

my @fns = map { substr($a,$_ - 1,1) eq 'm' ? "$fn a$_" : "pure a$_" }  (1 .. $n);
say "${tab}f ($c ", join(' ',@ds,@vs), ") = ",join(" ",$c,@ds), " <\$> ", join (" <*> ", @fns)