fix definition of single-letter options

	{

		// pipeline options

		cli |= lyra::opt(detect_features)

				["-f", "--detect-features"]

				["-f"]["--detect-features"]

				("Before mesh generation, detect sharp features and boundaries "

				 "of the internal bounding polyhedron (and the potential "

				 "internal polyhedron) and inserts them as features of the "

		// optimizer options

		cli |= lyra::opt(odt)

				["-o", "--odt"]

				["-o"]["--odt"]

				("Activate the optimal Delaunay triangulation smoother - a mesh "

				 "optimizer based on the minimization of a global energy "

				 "function." + fmt_default(perturb));

		cli |= lyra::opt(lloyd)

				["-l", "--lloyd"]

				["-l"]["--lloyd"]

				("Activate the Lloyd smoother - a mesh optimizer based on the "

				 "minimization of a global energy function."

				 + fmt_default(perturb));

		cli |= lyra::opt(perturb)

				["-p", "--perturb"]

				["-p"]["--perturb"]

				("Activate the perturber - a mesh optimizer that improves the "

				 "quality of a Delaunay mesh by changing the positions of some "

				 "vertices of the mesh." + fmt_default(perturb));

		cli |= lyra::opt(exude)

				["-e", "--exude"]

				["-e"]["--exude"]

				("Activate the exuder to exude slivers. The sliver exudation "

				 "process consists in optimizing the weights of vertices of the "

				 "weighted Delaunay triangulation in such a way that slivers "