m2_op_arith.hlp

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{smcl}
{* 18mar2005}{...}
{cmd:help m2 op_arith}
{hline}
{* index operators}{...}
{* index arithmetic operators}{...}
{* index product}{...}
{* index multiplication}{...}
{* index division}{...}
{* index addition}{...}
{* index subtraction}{...}
{* index power}{...}
{* index negation}{...}

{title:Title}

{p 4 4 2}
{hi:[M-2] op_arith -- Arithmetic operators}


{title:Syntax}

	{it:a} {cmd:+} {it:b}                      addition

	{it:a} {cmd:-} {it:b}                      subtraction

	{it:a} {cmd:*} {it:b}                      multiplication

	{it:a} {cmd:/} {it:b}                      division

	{it:a} {cmd:^} {it:b}                      power


	{cmd:-}{it:a}                         negation


{p 4 4 2}
where {it:a} and {it:b} may be numeric scalars, vectors, or matrices.


{title:Description}

{p 4 4 2}
The above operators perform basic arithmetic.


{title:Remarks}

{p 4 4 2}
Also see {bf:{help m2_op_colon:[M-2] op_colon}}
for the {cmd::+}, {cmd::-}, {cmd::*}, and {cmd::/} operators.  
Colon operators have relaxed conformability restrictions.

{p 4 4 2}
The {cmd:*} and {cmd::*} multiplication operators can also perform string
duplication -- 3*"a" = "aaa" -- see {bf:{help mf_strdup:[M-5] strdup()}}.


{title:Conformability}

	{it:a} {cmd:+} {it:b}, {it:a} {cmd:-} {it:b}:
		{it:a}:  {it:r x c}
		{it:b}:  {it:r x c}
	   {it:result}:  {it:r x c}

	{it:a} {cmd:*} {it:b}:
		{it:a}:  {it:k x n}      {it:k x n}      1 {it:x} 1
		{it:b}:  {it:n x m}      1 {it:x} 1      {it:n x m}
	   {it:result}:  {it:k x m}      {it:k x n}      {it:n x m}

	{it:a} {cmd:/} {it:b}:
		{it:a}:  {it:r x c}
		{it:b}:  1 {it:x} 1
	   {it:result}:  {it:r x c}

	{it:a} {cmd:^} {it:b}:
		{it:a}:  1 {it:x} 1
		{it:b}:  1 {it:x} 1
	   {it:result}:  1 {it:x} 1

	{cmd:-}{it:a}:
		{it:a}:  {it:r x c}
	   {it:result}:  {it:r x c}


{title:Diagnostics}

{p 4 4 2}
All operators return missing when arguments are missing.

{p 4 4 2}
{it:a}{cmd:*}{it:c} with {it:a}: {it:k} {it:x} 0 and {it:b}: 0 {it:x} {it:m}
returns a {it:k} {it:x} {it:m} matrix of zeros.

{p 4 4 2}
{it:a}{cmd:/}{it:b} returns missing when {it:b}==0 or when {it:a}{cmd:/}{it:b}
would result in overflow.

{p 4 4 2}
{it:a}{cmd:^}{it:b} returns a real when both {it:a} and {it:b} are real; 
thus {cmd:(-4)^.5} evaluates to missing, whereas 
{cmd:(-4+0i)^.5} evaluates to {cmd:2i}.

{p 4 4 2}
{it:a}{cmd:^}{it:b} returns missing on overflow.


{title:Also see}

{p 4 13 2}
Manual:  {hi:[M-2] op_arith}

{p 4 13 2}
Online:  help for 
{bf:{help m2_exp:[M-2] exp}};
{bf:{help m2_intro:[M-2] intro}}
{p_end}