@pindex calc-break-selections
The @kbd{j b} (@code{calc-break-selections}) command controls a mode
in which the ``deep structure'' of these associative formulas shows
-through. Calc actually stores the above formulas as @samp{((a + b) - c) + d}
-and @samp{x * (y * z)}. (Note that for certain obscure reasons, Calc
-treats multiplication as right-associative.) Once you have enabled
-@kbd{j b} mode, selecting with the cursor on the @samp{-} sign would
-only select the @samp{a + b - c} portion, which makes sense when the
-deep structure of the sum is considered. There is no way to select
-the @samp{b - c + d} portion; although this might initially look
-like just as legitimate a sub-formula as @samp{a + b - c}, the deep
-structure shows that it isn't. The @kbd{d U} command can be used
-to view the deep structure of any formula (@pxref{Normal Language Modes}).
+through. Calc actually stores the above formulas as
+@samp{((a + b) - c) + d} and @samp{x * (y * z)}. (Note that for certain
+obscure reasons, by default Calc treats multiplication as
+right-associative.) Once you have enabled @kbd{j b} mode, selecting
+with the cursor on the @samp{-} sign would only select the @samp{a + b -
+c} portion, which makes sense when the deep structure of the sum is
+considered. There is no way to select the @samp{b - c + d} portion;
+although this might initially look like just as legitimate a sub-formula
+as @samp{a + b - c}, the deep structure shows that it isn't. The @kbd{d
+U} command can be used to view the deep structure of any formula
+(@pxref{Normal Language Modes}).
When @kbd{j b} mode has not been enabled, the deep structure is
generally hidden by the selection commands---what you see is what
arguments in Calc's internal form. Sums and products of three or
more terms are arranged by the associative law of algebra into
a left-associative form for sums, @expr{((a + b) + c) + d}, and
-a right-associative form for products, @expr{a * (b * (c * d))}.
-Formulas like @expr{(a + b) + (c + d)} are rearranged to
-left-associative form, though this rarely matters since Calc's
-algebra commands are designed to hide the inner structure of
-sums and products as much as possible. Sums and products in
-their proper associative form will be written without parentheses
-in the examples below.
+(by default) a right-associative form for products,
+@expr{a * (b * (c * d))}. Formulas like @expr{(a + b) + (c + d)} are
+rearranged to left-associative form, though this rarely matters since
+Calc's algebra commands are designed to hide the inner structure of sums
+and products as much as possible. Sums and products in their proper
+associative form will be written without parentheses in the examples
+below.
Sums and products are @emph{not} rearranged according to the
commutative law (@expr{a + b} to @expr{b + a}) except in a few
@defvar calc-multiplication-has-precedence
The variable @code{calc-multiplication-has-precedence} determines
-whether multiplication has precedence over division in algebraic formulas
-in normal language modes. If @code{calc-multiplication-has-precedence}
-is non-@code{nil}, then multiplication has precedence, and so for
-example @samp{a/b*c} will be interpreted as @samp{a/(b*c)}. If
-@code{calc-multiplication-has-precedence} is @code{nil}, then
-multiplication has the same precedence as division, and so for example
+whether multiplication has precedence over division in algebraic
+formulas in normal language modes. If
+@code{calc-multiplication-has-precedence} is non-@code{nil}, then
+multiplication has precedence (and, for certain obscure reasons, is
+right associative), and so for example @samp{a/b*c} will be interpreted
+as @samp{a/(b*c)}. If @code{calc-multiplication-has-precedence} is
+@code{nil}, then multiplication has the same precedence as division
+(and, like division, is left associative), and so for example
@samp{a/b*c} will be interpreted as @samp{(a/b)*c}. The default value
of @code{calc-multiplication-has-precedence} is @code{t}.
@end defvar
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