J's "right to left evaluation" is a problem for students who know (and _should_ know) the
Algebraic Operating System of TI calculators. I wrote an introductory lab How J Works (for
university calculus students) whose closing panel is shown below. Cliff Reiter, could you share
your practical experience?
My take is that J is a valuable tool, and students should begin to learn how to
use it.
The ability to use labs is a bonus for the instructor.
You are going to have to deal with issues like 0.5 versus .5 , underscores versus hyphens, and
100x (extended precision) versus 100*x . Your students will encounter _ (infinity) and __
(minus infinity).
Another bonus for the instructor is, you can write utilities. My students had
for example
eit 2 3 ,: 1 4 NB. eigenvalue, eigenvector table
+-+--+
|5|1 |
+-+--+
|1|_3|
|1| 1|
+-+--+
and DF, an adverb for producing direction fields.
Here is the final panel of the How J Works lab. The first NO YES pair is a way to deal with
"right to left evaluation".
-- (26 of 27) Review ----------------------------------------
Review
i. n integers from 0 to n-1
a + h * i. n numbers from a to a+(n-1)h in steps of h
1 o. x sin x _1 o. x arcsin x ^ x e^x
2 o. x cos x _2 o. x arccos x ^. x ln x
3 o. x tan x _3 o. x arctan x %: x sqrt x
NO x-y x*y x^y a*x^y x%y f x
YES x+(-y) (x*y) (x^y) (a*x^y) (x%y) (f x)
pi =: 1p1 or pi =: 4 * _3 o. 1
row =: ,. &. |: usage x row (f x)
col =: ,. usage x col (f x)
f =: 3 : '1 + (y ^ 2)' use y for the x in f(x)
'title your name;grids on' plot 0 5;'(y^2)+1'
pd 'print 2000 2000'
NO _x YES _2 NO 3: YES 3 : NO .5 YES 0.5
)
Kip Murray
Math University of Houston, Retired
[email protected]
www.math.uh.edu/~km
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