first SRGA failure

rosalind/sgra-grondilu.pl

@@ -0,0 +1,47 @@
+use v6;
+use List::Utils;
+
+my %mass-table = slurp('monoisotopic-mass-table.txt').words;
+my @L = sort lines;
+# <1 132.04049>;
+# <3524.8542 3623.5245 3710.9335 3841.974 3929.00603 3970.0326 4026.05879 4057.0646 4083.08025>;
+my %invert-mass-table = %mass-table.invert.hash;
+# for %mass-table.invert { %invert-mass-table{.key}.push: .value }
+my @masses = sort +*, %mass-table.values;
+my %precision = @L Z=> map { $^x / $x.subst(/\./, '') }, @L;
+
+sub spectrum-graph(@L) {
+    my %edges;
+    for ^@L -> $i {
+	my $u = @L[$i];
+        for @L[$i+1..*-1] -> $v {
+            note my $precision = max %precision{$u, $v};
+	    my $diff = $v - $u;
+	    my $bound = upper-bound(@masses, $diff);
+	    my $mass = $bound == 0 ?? @masses[0] !!
+	    $bound == @masses.elems ?? @masses[*-1] !!
+	    min :by({abs($diff-$_)}), @masses[$bound-1, $bound];
+	    if abs($diff - $mass) < $precision {
+		#note "$i $precision $diff $mass";
+		%edges{$u}.push: {
+		    next-mass => $v,
+		    amino-acid => %invert-mass-table{$mass}
+		};
+	    }
+        }
+    }
+    return %edges;
+}
+
+my %graph = spectrum-graph(@L);
+sub find-protein($initial-mass) {
+    return '' unless %graph{$initial-mass} :exists;
+    gather for %graph{$initial-mass}[] -> $node {
+	take $node<amino-acid> «~« find-protein($node<next-mass>);
+    }
+}
+
+my @protein = map &find-protein, @L;
+say max :by(*.chars), @protein;
+
+# vim: ft=perl6