samer@0: % perm - arrow to permute inputs
samer@0: %
samer@0: % perm :: 
samer@0: %    N:natural ~'number of inputs',
samer@0: %    P:[[M]->[N]] ~'permutation of inputs'
samer@27: % -> arrow(_@typelist(N), _@typelist(M), empty).
samer@0: %
samer@0: % This function creates an arrow whos outputs can
samer@0: % be copies of any of the inputs in any order. 
samer@0: % For example,
samer@0: %    perm(5,[3,2,5])
samer@0: % is an arrow with 5 inputs and 3 outputs. Output
samer@0: % 1 is input 3, output 2 is input 2, and output 3 is
samer@0: % input 5.
samer@0: 
samer@0: function a=perm(nin,p)
samer@0: 	nout=length(p);
samer@0: 	a=arr(@permfn,'nargin',nin,'nargout',length(p));
samer@0: 
samer@0: 	function varargout=permfn(varargin)
samer@0: 		[varargout{1:nout}]=varargin{p};
samer@0: 	end
samer@0: end