[FEATURE] cigar.assign_string from char pointers.

include/seqan3/alphabet/cigar/cigar.hpp

@@ -182,6 +182,35 @@ class cigar : public alphabet_tuple_base<cigar, uint32_t, exposition_only::cigar
 
         return *this;
     }
+
+    /*!\brief Assign from a contigous char array.
+     * \details
+     *
+     * In order to avoid unnecessary copies, you can initialise a seqan3::cigar from two char pointers that point to a
+     * contigous char array that stores the cigar string.
+     *
+     * \include test/snippet/alphabet/cigar/cigar_assign_string.cpp
+     *
+     * \experimentalapi{Experimental since version 3.2.}
+     */
+    cigar & assign_string(char const * start, char const * end) noexcept
+    {
+        uint32_t num{};
+        auto [ ptr, errc ] = std::from_chars(start, end, num);
+
+        if ((errc != std::errc{}) || (!char_is_valid_for<operation>(*ptr)))
+        {
+            get<0>(*this) = 0;
+            assign_char_to('P', get<1>(*this));
+        }
+        else
+        {
+            get<0>(*this) = num;
+            assign_char_to(*ptr, get<1>(*this));
+        }
+
+        return *this;
+    }
     //!\}
 
     /*!\name Get functions

test/snippet/alphabet/cigar/cigar_assign_string.cpp

@@ -0,0 +1,16 @@
+#include <seqan3/alphabet/cigar/cigar.hpp>
+#include <seqan3/core/debug_stream.hpp>
+
+int main()
+{
+    std::string cigar_str{"4S134M"};
+
+    seqan3::cigar letter1{};
+    seqan3::cigar letter2{};
+
+    letter1.assign_string(cigar_str.data(), cigar_str.data() + 2);
+    letter2.assign_string(cigar_str.data() + 3, cigar_str.data() + cigar_str.size());
+
+    seqan3::debug_stream << letter1 << '\n';  // prints 134M
+    seqan3::debug_stream << letter2 << '\n';  // prints 134M
+}