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GNU Emacs Calc 2.02 Manual

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.)