Examining the Gp:getPointInput Function
When you ran the gp:getPointInput function, control was automatically passed from Visual LISP to AutoCAD. You responded
to three prompts, after which control was passed back from AutoCAD to Visual LISP,
and a T symbol displayed in the Console window.
Within the program, here is what happens:
- Visual LISP waits for you to pick the first point.
- When you pick the first point, the program stores the value of your selection (a
list containing three coordinate valuesâ€”an X, Y, and Z value) into the StartPt variable.
- The first if function examines the result to determine whether a valid value was entered or no
value was entered. When you pick a start point, control is passed to the next getpoint function.
- When you pick an endpoint, the point value is stored in the Endpt variable.
- The result of this statement is examined by the next if statement, and control is passed to the getdist function.
- The getdist function acts in a similar fashion when you pick a point on the screen or enter a
numeric value. The result of the getdist function is stored in the HalfWidth variable.
- Program flow reaches the T nested deeply within the function. No other functions follow this, so the function
ends, and the value T is returned. This is the T you see at the Console window.
You need some way to return values from one function to another. One way to do this
is to create a list of the values retrieved from gp:getPointInput, as highlighted in the following code:
(defun gp:getPointInput ( / StartPt EndPt HalfWidth ) (if (setq StartPt (getpoint " Start point of path: ")) (if (setq EndPt (getpoint StartPt " Endpoint of path: ")) (if (setq HalfWidth (getdist EndPt " half-width of path: ")) (list StartPt EndPt HalfWidth) ) ) ) )
Copy this version of gp:getPointInput into the Console window and press Enter. Here’s an opportunity to try another feature
of the Console window.
To use the Console window history feature to run gp:getPointInput
- Press Tab.
This invokes the Console history command, cycling through any commands previously
entered in the Console window. If you go too far, press Shift+Tab to cycle in the
- When you see (gp:getPointInput) at the Console prompt, press Enter to execute the function once again.
- Respond to the prompts as before.
The function returns a list containing two nested lists and a real (floating point)
value. The return values look like the following:
((4.46207 4.62318 0.0) (7.66688 4.62318 0.0) 0.509124)
These values correspond to the StartPt, EndPt, and HalfWidth variables.
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