HFCYL                                                              Menu: PRISM
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Creates a semi-circular prism (half cylinder) or a semi-circular polygon.

        1. * (CHAR) plane of base  semi-circle (x-xy,y-yz,  z-zx) <x>
        2. * (NUM) option: (0-top half /3-right half /6-bottom half /9-left
                   half) <0>
        3. * (POINT) diameter starting point
        4. * (NUM) diameter (greater than 0)
     for option `x':
        5. * (NUM) height of prism
     for option `y' or `z':
        5. * (NUM) length of prism
     for all options:
        6. * (Y/N) positive prism? <y>

Description:
This command creates a semi-circular (2D) polygon or a semi-circular prism
based on that polygon. Specify the base plane (one of the axial planes; x  xy
plane [the default], y  yz plane or z  xz plane). Choose one of the options
for the semi-circle orientation: 0  top half, 3  left half, 6  bottom half, or
9   right half (the default is 0)
Define the starting point and diameter. Give a height (for option `x') or the
width (for options `y' or `z'). You may enter `0' for a 2D polygon. Specify
whether the solid is to be positive (option `y', the default) or negative
(option `n').
You are prompted to create additional half-cylinders until another command is
selected.

        Example: \hfcyl x 0 3 3 0 4 1 y

Result: A half-cylinder is created with its diameter starting point at 3 3 0,
a diameter of 4 units (meters or feet), and a height of 1 unit.
