Page 22-33
An example of a program using GROB
The following program produces the graph of the sine function including a
frame – drawn with the function BOX – and a GROB to label the graph.
Here is the listing of the program:
«
Begin
program
RAD
Set
angle
units
to
radians
131 R
B 64 R
B PDIM
Set PICT screen to 131
×
64 pixels
-6.28 6.28 XRNG –2. 2. YRNG
Set x- and y-ranges
FUNCTION
Select FUNCTION type for graphs
‘SIN(X)’ STEQ
Store the function sine into EQ
ERASE DRAX LABEL DRAW
Clear, draw axes, labels, graph
(-6.28,-2.) (6.28,2.) BOX
Draw a frame around the graph
PICT RCL
Place contents of PICT on stack
“SINE FUNCTION”
Place graph label string in stack
1
GROB
Convert string into a small GROB
(-6., 1.5) SWAP
Coordinates to place label GROB
GOR
Combine PICT with the label GROB
PICT STO
Save combined GROB into PICT
{ } PVIEW
Bring PICT to the stack
»
End
program
Save the program under the name GRPR (GROB PRogram). Press
@GRPR
to run
the program. The output will look like this:
A program with plotting and drawing functions
In this section we develop a program to produce, draw and label Mohr’s
circle for a given condition of two-dimensional stress. The left-hand side
figure below shows the given state of stress in two-dimensions, with
σ
xx
and
σ
yy
being normal stresses, and
τ
xy
=
τ
yx
being shear stresses. The right-hand
