{smcl}
{bf:Mata course:  Interpretive commands}
{hline}


{title:Syntax}

{p 4 8 2}
    They are used from the Mata colon (:) prompt.

{p 4 8 2}
    They start with the word {cmd:mata}.

{p 4 8 2}
    They are documented in {bf:{help m3_intro:[M-3]}}.

{p 4 8 2}
    They describe and manipulate the environment you are in {bf:RIGHT NOW}.

{p 4 8 2}
    Mata programs are compiled.  They run {bf:LATER}.

{p 4 8 2}
    Mata programs never use Mata interpretive commands.


{title:mata describe and mata clear}

	{com}. mata
	{txt}{hline 49} mata (type {cmd:end} to exit) {hline}
	{com}: mata describe

      	      {txt}# bytes   type                        name and extent
	{hline 71}
	{res}           76   {txt}transmorphic matrix         {res}add{txt}()
	{res}          200   {txt}real matrix                 {res}id{txt}()
	{res}           32   {txt}real matrix                 {res}A{txt}[2,2]
	{res}           32   {txt}real matrix                 {res}B{txt}[2,2]
	{res}           72   {txt}real matrix                 {res}I3{txt}[3,3]
	{res}           48   {txt}real matrix                 {res}M{txt}[3,2]
	{res}           48   {txt}real matrix                 {res}S{txt}[3,2]
	{res}           72   {txt}real matrix                 {res}X{txt}[3,3]
	{res}           72   {txt}real matrix                 {res}Xi{txt}[3,3]
	{res}           64   {txt}complex matrix              {res}Z{txt}[2,2]
	{res}           16   {txt}real colvector              {res}a{txt}[2]
	{res}           16   {txt}complex scalar              {res}acomplex
	            8   {txt}real scalar                 {res}areal
	           16   {txt}real colvector              {res}b{txt}[2]
	{res}           32   {txt}real colvector              {res}c{txt}[4]
	{res}            8   {txt}real scalar                 {res}findout
	           16   {txt}real rowvector              {res}x{txt}[2]
	{res}           16   {txt}real rowvector              {res}y{txt}[2]
	{res}           32   {txt}real rowvector              {res}z{txt}[4]
	{hline 71}{txt}

	{com}: mata clear

	{com}: mata describe

	      {txt}# bytes   type                        name and extent
	{hline 71}
	{hline 71}{txt}


{p 4 4 2}
Mata's {cmd:mata clear} command clears Mata.

{p 4 4 2}
Stata's {cmd:clear} command also clears Mata, and lots more.


{title:mata query and mata set}

	{com}: mata query 
	{txt}{hline}
	    Mata settings
{col 17}{help mata_set:set matastrict}{col 37}{res}off
{txt}{col 17}{help mata_set:set matalnum}{col 37}{res}off
{txt}{col 17}{help mata_set:set mataoptimize}{col 37}{res}on
{txt}{col 17}{help mata_set:set matafavor}{col 37}{res}space{txt}{col 48}may be {res:space} or {res:speed}
{col 17}{help mata_set:set matacache}{col 37}{res}400{txt}{col 48}kilobytes
{col 17}{help mata_set:set matalibs}{col 37}{res}lmatabase;lmataado
{txt}{col 17}{help mata_set:set matamofirst}{col 37}{res}off


	{com}: mata set matafavor speed

	{com}: mata query 
	{txt}{hline}
	    Mata settings
{col 17}{help mata_set:set matastrict}{col 37}{res}off
{txt}{col 17}{help mata_set:set matalnum}{col 37}{res}off
{txt}{col 17}{help mata_set:set mataoptimize}{col 37}{res}on
{txt}{col 17}{help mata_set:set matafavor}{col 37}{res}speed{txt}{col 48}may be {res:space} or {res:speed}
{col 17}{help mata_set:set matacache}{col 37}{res}400{txt}{col 48}kilobytes
{col 17}{help mata_set:set matalibs}{col 37}{res}lmatabase;lmataado
{txt}{col 17}{help mata_set:set matamofirst}{col 37}{res}off


{title:mata which}

	{com}: mata which I()
	  {txt}I():  built-in

	{com}: mata which solvelower()
	  {txt}solvelower():  lmatabase

	{com}: mata which recorr()
	{err}function recorr() not found
	{txt}{search r(111):r(111);}


{p 4 4 2}
Implications:

{p 8 11 2}
-- You {bf:CANNOT} look at the source for {cmd:I()}

{p 8 11 2}
-- You {bf:CAN} look at the source for {cmd:solvelower()}

{p 8 11 2}
-- No function named {cmd:recorr()} exists

{p 8 11 2}
-- You {bf:CANNOT} create a function named {cmd:I()}

{p 8 11 2}
-- You {bf:CAN} create a function named {cmd:solvelower()} (surprise!){break}
   (You do not want to unless You are fixing a bug)

{p 8 11 2}
-- You {bf:CAN} create a function named {cmd:recorr()}


{title:mata mosave and mata mlib}

{p 8 12 2}
-- You can use {cmd:mata mosave} to create {cmd:.mo} files.

{p 8 12 2}
-- You can use {cmd:mata mlib} to create {cmd:.mlib} files.

{p 8 12 2}
-- They contain compiled source code (object code).

{p 8 12 2}
-- {cmd:.mo} files contain object code for one (1) function.

{p 8 12 2}
-- {cmd:.mlib} files contain object codes for lots of functions (up to 500).

{p 4 4 2}
All of that is getting ahead of ourselves.

{p 4 4 2}
Even sophisticated programmers may never need these features.


{title:Other interpretive commands}

{p 4 4 2}
Rarely used.


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{bf:{view talk.smcl:Top}}