// t_format_varfld_1.d                                      12oct18waw

// for pm#1223893

// compile:
//  dmd t_format_varfld_1.d

// invoke:
//  t_format_varfld_1  n  1 [ 0 1 ... ]
// where:
//  n               group size of output string.
//  1 [ 0 1 ... ]   bits to be grouped.  can be any integer; only
//                  least significant bit will be printed.

immutable USAGE = "
invoke:
 t_format_varfld_1  n  1 [ 0 1 ... ]
where:
 n               required: group size of output string.
 1 [ 0 1 ... ]   one or more bits to be grouped.  can be any integer;
                 only least significant bit will be processed.
";

int main (string [] args) {

    import std.stdio     : writeln, writefln;
    import std.conv      : to;
    import std.array     : array, popFront, front;
    import std.algorithm : map;

    args.popFront;  // discard program name

    if (! args.length) {
        writeln("no group size given", USAGE);
        return(1);
        }
    const N = args.front.to!size_t;

    args.popFront;  // discard group size

    if (! args.length) {
        writeln("no bits/ints given", USAGE);
        return(1);
        }
    auto bits = args.map!"a.to!uint".array;

    auto str = str_groups(N, bits);
    writefln("%s -> '%s'", bits, str);

    return(0);

    }  // end main()


auto str_groups (T = typeof(N), B = typeof(bits[])) (in T n, B [] b) {

    import std.format    : format;
    import std.range     : chunks;
    import std.algorithm : map;

    return b                    // for input array...
        .map !"a &= 1"          // 1. only process lsb of each charact
+er
        .chunks(n)              // 2. partition array into sub-arrays
        .format !"%(%(%b%) %)"  // 3. format each sub-array into strin
+g
        ;                       // 4. return formatted string of strin
+gs

    }
[download]

C:\@Work\DMD2\posts\Anonymous Monk\1223893>t_format_varfld_1  3  1 0 1
+ 1 0 0 1 0 1 0 1 0
[1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0] -> '101 100 101 010'

C:\@Work\DMD2\posts\Anonymous Monk\1223893>t_format_varfld_1  4  1 0 1
+ 1 0 0 1 0 1 0 1 0
[1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0] -> '1011 0010 1010'

C:\@Work\DMD2\posts\Anonymous Monk\1223893>t_format_varfld_1  5  1 0 1
+ 1 0 0 1 0 1 0 1 0
[1, 0, 1, 1, 0, 0, 1, 0, 1, 0, 1, 0] -> '10110 01010 10'
[download]