174 Section 12: Calculating with Matrices
Pressing ´mV dimensions the matrix specified in R
I
according to the dimensions in the X- and Y-registers.
Pressing lmV recalls to the X- and Y-registers the
dimensions of the matrix specified in R
I
.
Pressing GV or tV has the same result as pressing
G or t followed by the letter of the matrix specified in R
I
.
(This is not actually a matrix operation only the letter in the
matrix descriptor is used.)
Conditional Tests on Matrix Descriptors
Four conditional tests ~, T 0 (x 0), T 5 (x = y), and T
6 (xy) can be performed with matrix descriptors in the X- and Y-
registers, Conditional tests can be used to control program execution, as
described in section 8.
If a matrix descriptor is in the X-register, the result of ~ will be false
and the result of T 0 will be true (regardless of the element values in
the matrix.)
If matrix descriptors are in the X- and Y-registers when T 5 or T 6
conditional test is performed, x and y are equal if the same descriptor is in
the X- and Y-registers, and not equal otherwise. The comparison is made
between the descriptors themselves, not between the elements of the
specified matrices.
Other conditional tests can't be used with matrix descriptors.
Stack Operation for Matrix Calculations
During matrix calculations, the contents of the stack registers shift much
like they do during numeric calculations.
For some matrix calculations, the result is stored in the result matrix. The
arguments one or two descriptors or numbers in the X-register or the X-
and Y-registers are combined by the operation, and the descriptor of the
result matrix is placed in the X-register. (The argument from the X-register
is placed in the LAST X register.)
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