#### One-a-Day: FRAG

The FRAG primitive creates a filled shape out of the current turtle position and her last two positions. For example:

FD 100 RT 90 FD 100 FRAG

will create a triangle.

While turtleSpaces has a variety of shape primitives, sometimes you need to create an arbitrary shape, and FRAG aids you in this.

Take this example, which draws a star:

```TO star
repeat 4 [
forward 100
right 170
forward 86
frag
left 70
forward 86
right 170
forward 100
frag
right 180
]
```

We can change the number of sides the star has by changing the number of repeats and fiddling with the values a bit:

```TO star2
repeat 5 [
fd 100 rt 170
fd 86 frag
lt 88 fd 86
rt 170 fd 100
frag rt 180
]
END
```

First, let’s change our star procedures so they can take a :size parameter, like so:

```TO star1 :size
repeat 4 [
fd 100 * :size
rt 170
fd 86 * :size
frag
lt 70
fd 86 * :size
rt 170
fd 100 * :size
frag
rt 180
]
END
```

In this case, :size is a ratio, that is, 0.5 will make a star half the size, and 2 will make a star twice the size of the default.

You can change the color of the star using the SETFILLCOLOR primitive, or set a random fill color with RANDFC.

The following procedures create a sky full of stars:

```TO star1 :size
repeat 4 [
fd 100 * :size
rt 170
fd 86 * :size
frag
lt 70
fd 86 * :size
rt 170
fd 100 * :size
frag
rt 180
]
END

TO star2 :size
repeat 5 [fd 100 * :size rt 170 fd 86 * :size frag lt 88 fd 86 * :size rt 170 fd 100 * :size frag rt 180]
END

TO star3 :size
repeat 6 [fd 100 * :size rt 170 fd 86 * :size frag lt 100 fd 86 * :size rt 170 fd 100 * :size frag rt 180]
END

TO star4 :size
repeat 7 [fd 100 * :size rt 170 fd 86 * :size frag lt 108.625 fd 86 * :size rt 170 fd 100 * :size frag rt 180]
END

TO star5 :size
repeat 8 [fd 100 * :size rt 170 fd 86 * :size frag lt 115 fd 86 * :size rt 170 fd 100 * :size frag rt 180]
END

TO stars
reset cam:setposition [0 0 0]
cam:fixate [0 0 0]
cam:setviewpoint [0 0 0]
cam:newworker [forever [up 0.1 lt 0.1 rr 0.1 wait 1]]
repeat 200 [
pu home randori fd 400 + random 1000 up 90
lt random 60 pd randpc randfc randfs randps
make "size (10 + random 90) / 100
run {pick [star1 star2 star3 star4 star5] :size}
]

END

```

Type STARS and press Enter to see the stars!

FRAG’s sister, SHARD creates a three-dimensional FRAG with depth beneath it. This depth is supplied as a parameter, in turtle-units, eg. SHARD 5. Try replacing FRAG with SHARD 5 in one of your star procedures and see what happens! (You’ll need to drag the camera around to see the sides of the star)