Appearance
Constraints
Constraints say how elements relate: how far apart two points are, which line a point is on, which way a line runs. Each is a line of the program on its own, or follows on from the line before it in the same sentence:
line l parallel m -- make l, then: l is parallel to m
l through p -- said on its own
line l parallel m through pA constraint gives back the thing it was said about, which is what lets the next one in the sentence be about the same thing. How a line is read is on Reading a Line.
Position
Puts a point at given coordinates.
p at 3 5
point p at 3 5 -- make p and put it there
point p = (3, 5) -- the sameDistance
Fixes the distance between two points, and draws the segment between them.
distance between a and b is 5click to pan & zoom
Same point
Two points are the same point.
p = qFor now they are held at no distance apart — still two points, drawn on top of each other.
On a line
A point lies on a line. Its place along the line is open unless something else pins it down.
p on l
point p on l -- make p on lThe same thing said from the line's side:
l through p
line l through p q -- make the line through two pointsclick to pan & zoom
b can be 3 from a on either side of it along l, so both places are shown.
On a circle
A point lies on a circle. On one circle it can slide round; with a line or a second circle it is where they cross.
p on c
point p on cWhen three or more points are known to lie on the same circle, its centre and radius are worked out. See Circle.
Parallel
Two lines run the same way.
l parallel m
line l parallel m -- make l parallel to mAdd at for the distance between them. That has two answers, one on each side.
l parallel m at 3Perpendicular
Two lines meet at a right angle.
l perpendicular m
line l perpendicular mAdd at to name where they cross:
l perpendicular m at p -- p is on bothComing back
Angles, a point on a segment and a few other constraints went with Tilde's older syntax and are not here yet. They are listed on the roadmap.