The functions described here perform various operations on the Calc stack and trail. They are to be used in interactive Calc commands.

__Function:__ **calc-push-list** *vals n*

Push the Calc objects in list `vals` onto the stack at stack level
`n`. If `n` is omitted it defaults to 1, so that the elements
are pushed at the top of the stack. If `n` is greater than 1, the
elements will be inserted into the stack so that the last element will
end up at level `n`, the next-to-last at level `n`+1, etc.
The elements of `vals` are assumed to be valid Calc objects, and
are not evaluated, rounded, or renormalized in any way. If `vals`
is an empty list, nothing happens.

The stack elements are pushed without any sub-formula selections.
You can give an optional third argument to this function, which must
be a list the same size as `vals` of selections. Each selection
must be `eq`

to some sub-formula of the corresponding formula
in `vals`, or `nil`

if that formula should have no selection.

__Function:__ **calc-top-list** *n m*

Return a list of the `n` objects starting at level `m` of the
stack. If `m` is omitted it defaults to 1, so that the elements are
taken from the top of the stack. If `n` is omitted, it also
defaults to 1, so that the top stack element (in the form of a
one-element list) is returned. If `m` is greater than 1, the
`m`th stack element will be at the end of the list, the `m`+1st
element will be next-to-last, etc. If `n` or `m` are out of
range, the command is aborted with a suitable error message. If `n`
is zero, the function returns an empty list. The stack elements are not
evaluated, rounded, or renormalized.

If any stack elements contain selections, and selections have not
been disabled by the `j e` (`calc-enable-selections`

) command,
this function returns the selected portions rather than the entire
stack elements. It can be given a third "selection-mode" argument
which selects other behaviors. If it is the symbol `t`

, then
a selection in any of the requested stack elements produces an
"illegal operation on selections" error. If it is the symbol `full`

,
the whole stack entry is always returned regardless of selections.
If it is the symbol `sel`

, the selected portion is always returned,
or `nil`

if there is no selection. (This mode ignores the `j e`
command.) If the symbol is `entry`

, the complete stack entry in
list form is returned; the first element of this list will be the whole
formula, and the third element will be the selection (or `nil`

).

__Function:__ **calc-pop-stack** *n m*

Remove the specified elements from the stack. The parameters `n`
and `m` are defined the same as for `calc-top-list`

. The return
value of `calc-pop-stack`

is uninteresting.

If there are any selected sub-formulas among the popped elements, and
`j e` has not been used to disable selections, this produces an
error without changing the stack. If you supply an optional third
argument of `t`

, the stack elements are popped even if they
contain selections.

__Function:__ **calc-record-list** *vals tag*

This function records one or more results in the trail. The `vals`
are a list of strings or Calc objects. The `tag` is the four-character
tag string to identify the values. If `tag` is omitted, a blank tag
will be used.

__Function:__ **calc-normalize** *n*

This function takes a Calc object and "normalizes" it. At the very least this involves re-rounding floating-point values according to the current precision and other similar jobs. Also, unless the user has selected no-simplify mode (see section Simplification Modes), this involves actually evaluating a formula object by executing the function calls it contains, and possibly also doing algebraic simplification, etc.

__Function:__ **calc-top-list-n** *n m*

This function is identical to `calc-top-list`

, except that it calls
`calc-normalize`

on the values that it takes from the stack. They
are also passed through `check-complete`

, so that incomplete
objects will be rejected with an error message. All computational
commands should use this in preference to `calc-top-list`

; the only
standard Calc commands that operate on the stack without normalizing
are stack management commands like `calc-enter`

and `calc-roll-up`

.
This function accepts the same optional selection-mode argument as
`calc-top-list`

.

__Function:__ **calc-top-n** *m*

This function is a convenient form of `calc-top-list-n`

in which only
a single element of the stack is taken and returned, rather than a list
of elements. This also accepts an optional selection-mode argument.

__Function:__ **calc-enter-result** *n tag vals*

This function is a convenient interface to most of the above functions.
The `vals` argument should be either a single Calc object, or a list
of Calc objects; the object or objects are normalized, and the top `n`
stack entries are replaced by the normalized objects. If `tag` is
non-`nil`

, the normalized objects are also recorded in the trail.
A typical stack-based computational command would take the form,

(calc-enter-resultntag(cons 'calcFunc-func(calc-top-list-nn)))

If any of the `n` stack elements replaced contain sub-formula
selections, and selections have not been disabled by `j e`,
this function takes one of two courses of action. If `n` is
equal to the number of elements in `vals`, then each element of
`vals` is spliced into the corresponding selection; this is what
happens when you use the `TAB` key, or when you use a unary
arithmetic operation like `sqrt`

. If `vals` has only one
element but `n` is greater than one, there must be only one
selection among the top `n` stack elements; the element from
`vals` is spliced into that selection. This is what happens when
you use a binary arithmetic operation like `+`. Any other
combination of `n` and `vals` is an error when selections
are present.

__Function:__ **calc-unary-op** *tag func arg*

This function implements a unary operator that allows a numeric prefix
argument to apply the operator over many stack entries. If the prefix
argument `arg` is `nil`

, this uses `calc-enter-result`

as outlined above. Otherwise, it maps the function over several stack
elements; see section Numeric Prefix Arguments. For example,

(defun calc-zeta (arg) (interactive "P") (calc-unary-op "zeta" 'calcFunc-zeta arg))

__Function:__ **calc-binary-op** *tag func arg ident unary*

This function implements a binary operator, analogously to
`calc-unary-op`

. The optional `ident` and `unary`
arguments specify the behavior when the prefix argument is zero or
one, respectively. If the prefix is zero, the value `ident`
is pushed onto the stack, if specified, otherwise an error message
is displayed. If the prefix is one, the unary function `unary`
is applied to the top stack element, or, if `unary` is not
specified, nothing happens. When the argument is two or more,
the binary function `func` is reduced across the top `arg`
stack elements; when the argument is negative, the function is
mapped between the next-to-top *- arg* stack elements and the
top element.

__Function:__ **calc-stack-size**

Return the number of elements on the stack as an integer. This count does not include elements that have been temporarily hidden by stack truncation; see section Truncating the Stack.

__Function:__ **calc-cursor-stack-index** *n*

Move the point to the `n`th stack entry. If `n` is zero, this
will be the ``.'` line. If `n` is from 1 to the current stack size,
this will be the beginning of the first line of that stack entry's display.
If line numbers are enabled, this will move to the first character of the
line number, not the stack entry itself.

__Function:__ **calc-substack-height** *n*

Return the number of lines between the beginning of the `n`th stack
entry and the bottom of the buffer. If `n` is zero, this
will be one (assuming no stack truncation). If all stack entries are
one line long (i.e., no matrices are displayed), the return value will
be equal `n`+1 as long as `n` is in range. (Note that in Big
mode, the return value includes the blank lines that separate stack
entries.)

__Function:__ **calc-refresh**

Erase the `*Calculator*`

buffer and reformat its contents from memory.
This must be called after changing any parameter, such as the current
display radix, which might change the appearance of existing stack
entries. (During a keyboard macro invoked by the `X` key, refreshing
is suppressed, but a flag is set so that the entire stack will be refreshed
rather than just the top few elements when the macro finishes.)

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