# multigrid.pf
# aym3ric-at-goto10-dot-org
# a 2 dimensions grid list generator, useful to generate a list of
# coordinates for a whole section of the display
#
# ATM, multigrid takes as input 3 numbers
# - the length (X)
# - the height (Y)
# - the number of elements to generate for each side
#
# example:
# to create a 1 by 1 grid made of 16 nodes
#
# 1 1 4 multigrid
#
# TODO: make a n-dimensions version


# "interpol.pf" load

: multigrid
        dup >r
        3 pack dup unpack
        # we compute the top horizontal block
        >r
        >float 2. / >r
        >float 2. / -1. * r> swap 2 pack
        dup unpack abs 2 pack
        r> 1 - 3 pack reverse 1 pack interpol
        # we compute the interval
        >r
        unpack
        dup >r
        >float >r >float r> 1. - / nip
        0. 2 pack dup r> 1 - 3 pack reverse 1 pack interpol
        r>
        # we compute all the horizontal blocks
        swap >r dup >r >list r> r>
        r> 1 - dup >r for dup >r - dup >list swap r> next
        drop drop
        r> for concat next
        ;