mf_valofexternal.hlp

是一个经济学管理应用软件 很难找的 但是经济学学生又必须用到

{smcl}
{* 23mar2005}{...}
{cmd:help mata valofexternal()}
{hline}
{* index valofexternal()}{...}
{* index externals}{...}
{* index global variable}{...}

{title:Title}

{p 4 4 2}
{bf:[M-5] valofexternal() -- Obtain value of external global}


{title:Syntax}

{p 8 12 2}
{it:transmorphic matrix}
{cmd:valofexternal(}{it:string scalar name}{cmd:)}


{title:Description}

{p 4 4 2}
{cmd:valofexternal(}{it:name}{cmd:)} returns the contents of the
external global matrix, vector, or scalar whose name is specified by
{it:name}; it returns J(0,0,.) if the external global is not found.

{p 4 4 2}
Also see {it:Linking to external globals} in 
{bf:{help m2_declarations:[M-2] declarations}}.


{title:Remarks}

{p 4 4 2}
Also see {bf:{help mf_findexternal:[M-5] findexternal()}}.  Rather than
returning a pointer to the external global, as does {cmd:findexternal()},
{cmd:valofexternal()} returns the contents of the external global.  This
is useful when the external global contains a scalar:

	{cmd:tol = valofexternal("tolerance")}
	{cmd:if (tol==J(0,0,.)) tol = 1e-6}

{p 4 4 2}
Using {cmd:findexternal()}, one alternative would be

	{cmd}if ((p = findexternal("tolerance"))==NULL) tol = 1e-6
	else tol = *p{txt}

{p 4 4 2}
For efficiency reasons, use of {cmd:valofexternal()} should be avoided 
with nonscalar objects; see {bf:{help mf_findexternal:[M-5] findexternal()}}.


{title:Conformability}

    {cmd:valofexternal(}{it:name}{cmd:)}:
	     {it:name}:  1 {it:x} 1
	   {it:result}:  {it:r x c}  or  0 {it:x} 0 if not found


{title:Diagnostics}

{p 4 4 2}
{cmd:valofexternal()} aborts with error if {it:name} contains an invalid name.

{p 4 4 2}
{cmd:valofexternal(}{it:name}{cmd:)} returns J(0,0,.) if {it:name} does not 
exist.


{title:Also see}

{p 4 13 2}
Manual:  {hi:[M-5] valofexternal()}

{p 4 13 2}
Online:  help for 
{bf:{help mf_findexternal:[M-5] findexternal()}};
{bf:{help m4_programming:[M-4] programming}}
{p_end}