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GNU Emacs Calc 2.02 Manual

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3.7.4 RPN Tutorial Exercise 4

Either ( 2 , 3 ) or ( 2 SPC 3 ) would have worked, but using both the comma and the space at once yields:

 
1:  ( ...      2:  ( ...      1:  (2, ...    2:  (2, ...    2:  (2, ...
    .          1:  2              .          1:  (2, ...    1:  (2, 3)
                   .                             .              .

    (              2              ,             SPC            3 )

Joe probably tried to type TAB DEL to swap the extra incomplete object to the top of the stack and delete it. But a feature of Calc is that DEL on an incomplete object deletes just one component out of that object, so he had to press DEL twice to finish the job.

 
2:  (2, ...    2:  (2, 3)     2:  (2, 3)     1:  (2, 3)
1:  (2, 3)     1:  (2, ...    1:  ( ...          .
    .              .              .

                  TAB            DEL            DEL

(As it turns out, deleting the second-to-top stack entry happens often enough that Calc provides a special key, M-DEL, to do just that. M-DEL is just like TAB DEL, except that it doesn't exhibit the "feature" that tripped poor Joe.)


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