git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@9525 f3b2605a-c512-4ea7-a41b-209d697bcdaa

doc/Section_commands.html

@@ -100,13 +100,34 @@ single leading "#" will comment out the entire command.
 </P>
 <P>(3) The line is searched repeatedly for $ characters, which indicate
 variables that are replaced with a text string.  See an exception in
-(6).  If the $ is followed by curly brackets, then the variable name
+(6).
-is the text inside the curly brackets.  If no curly brackets follow
+</P>
-the $, then the variable name is the single character immediately
+<P>If the $ is followed by curly brackets, then the variable name is the
-following the $.  Thus ${myTemp} and $x refer to variable names
+text inside the curly brackets.  If no curly brackets follow the $,
-"myTemp" and "x".  See the <A HREF = "variable.html">variable</A> command for
+then the variable name is the single character immediately following
-details of how strings are assigned to variables and how they are
+the $.  Thus ${myTemp} and $x refer to variable names "myTemp" and
-substituted for in input script commands.
+"x". 
+</P>
+<P>If the $ is followed by parenthesis, then the text inside the
+parenthesis is treated as an "immediate" variable and evaluated as an
+<A HREF = "variable.html">equal-style variable</A>.  This is a way to use numeric
+formulas in an input script without having to assign them to variable
+names.  For example, these 3 input script lines:
+</P>
+<PRE>variable X equal (xlo+xhi)/2+sqrt(v_area)
+region 1 block $X 2 INF INF EDGE EDGE
+variable X delete 
+</PRE>
+<P>can be replaced by 
+</P>
+<PRE>region 1 block $((xlo+xhi)/2+sqrt(v_area)) 2 INF INF EDGE EDGE 
+</PRE>
+<P>The latter produces an identical result, without having to define and
+discard a temporary variable X.
+</P>
+<P>See the <A HREF = "variable.html">variable</A> command for more details of how
+strings are assigned to variables and evaluated, and how they can be
+used in input script commands.
 </P>
 <P>(4) The line is broken into "words" separated by whitespace (tabs,
 spaces).  Note that words can thus contain letters, digits,
@@ -120,12 +141,13 @@ it can be enclosed in either double or single quotes.  E.g.
 </P>
 <PRE>print "Volume = $v"
 print 'Volume = $v' 
+if "$<I>steps</I> > 1000" then quit 
 </PRE>
 <P>The quotes are removed when the single argument is stored internally.
-See the <A HREF = "dump_modify.html">dump modify format</A> or <A HREF = "if.html">if</A> commands
+See the <A HREF = "dump_modify.html">dump modify format</A> or <A HREF = "print.html">print</A> or
-for examples.  A "#" or "$" character that is between quotes will not
+<A HREF = "if.html">if</A> commands for examples.  A "#" or "$" character that is
-be treated as a comment indicator in (2) or substituted for as a
+between quotes will not be treated as a comment indicator in (2) or
-variable in (3).
+substituted for as a variable in (3). 
 </P>
 <P>IMPORTANT NOTE: If the argument is itself a command that requires a
 quoted argument (e.g. using a <A HREF = "print.html">print</A> command as part of an

doc/Section_commands.txt

@@ -96,13 +96,34 @@ single leading "#" will comment out the entire command.
 
 (3) The line is searched repeatedly for $ characters, which indicate
 variables that are replaced with a text string.  See an exception in
-(6).  If the $ is followed by curly brackets, then the variable name
+(6).
-is the text inside the curly brackets.  If no curly brackets follow
+
-the $, then the variable name is the single character immediately
+If the $ is followed by curly brackets, then the variable name is the
-following the $.  Thus $\{myTemp\} and $x refer to variable names
+text inside the curly brackets.  If no curly brackets follow the $,
-"myTemp" and "x".  See the "variable"_variable.html command for
+then the variable name is the single character immediately following
-details of how strings are assigned to variables and how they are
+the $.  Thus $\{myTemp\} and $x refer to variable names "myTemp" and
-substituted for in input script commands.
+"x". 
+
+If the $ is followed by parenthesis, then the text inside the
+parenthesis is treated as an "immediate" variable and evaluated as an
+"equal-style variable"_variable.html.  This is a way to use numeric
+formulas in an input script without having to assign them to variable
+names.  For example, these 3 input script lines:
+
+variable X equal (xlo+xhi)/2+sqrt(v_area)
+region 1 block $X 2 INF INF EDGE EDGE
+variable X delete :pre
+
+can be replaced by 
+
+region 1 block $((xlo+xhi)/2+sqrt(v_area)) 2 INF INF EDGE EDGE :pre
+
+The latter produces an identical result, without having to define and
+discard a temporary variable X.
+
+See the "variable"_variable.html command for more details of how
+strings are assigned to variables and evaluated, and how they can be
+used in input script commands.
 
 (4) The line is broken into "words" separated by whitespace (tabs,
 spaces).  Note that words can thus contain letters, digits,
@@ -115,13 +136,14 @@ line are arguments.
 it can be enclosed in either double or single quotes.  E.g.
 
 print "Volume = $v"
-print 'Volume = $v' :pre
+print 'Volume = $v' 
+if "${steps} > 1000" then quit :pre
 
 The quotes are removed when the single argument is stored internally.
-See the "dump modify format"_dump_modify.html or "if"_if.html commands
+See the "dump modify format"_dump_modify.html or "print"_print.html or
-for examples.  A "#" or "$" character that is between quotes will not
+"if"_if.html commands for examples.  A "#" or "$" character that is
-be treated as a comment indicator in (2) or substituted for as a
+between quotes will not be treated as a comment indicator in (2) or
-variable in (3).
+substituted for as a variable in (3). 
 
 IMPORTANT NOTE: If the argument is itself a command that requires a
 quoted argument (e.g. using a "print"_print.html command as part of an

doc/read_data.html

@@ -74,8 +74,8 @@ header line(s) and section(s) that it reads from the data file.
 spacing between words and numbers) is not important except that header
 and section keywords (e.g. atoms, xlo xhi, Masses, Bond Coeffs) must
 be capitalized as shown and can't have extra white space between their
-words - e.g. two spaces or a tab between "Bond" and "Coeffs" is not
+words - e.g. two spaces or a tab between the 2 words in "xlo xhi" or
-valid.
+the 2 words in "Bond Coeffs", is not valid.
 </P>
 <HR>
 

doc/read_data.txt

@@ -68,8 +68,8 @@ The formatting of individual lines in the data file (indentation,
 spacing between words and numbers) is not important except that header
 and section keywords (e.g. atoms, xlo xhi, Masses, Bond Coeffs) must
 be capitalized as shown and can't have extra white space between their
-words - e.g. two spaces or a tab between "Bond" and "Coeffs" is not
+words - e.g. two spaces or a tab between the 2 words in "xlo xhi" or
-valid.
+the 2 words in "Bond Coeffs", is not valid.
 
 :line
 

doc/variable.html

@@ -119,8 +119,8 @@ evaluation of the string.  Note that the same string can generate
 different values when it is evaluated at different times during a
 simulation.
 </P>
-<P>IMPORTANT NOTE: When the input script line that defines a variable of
+<P>IMPORTANT NOTE: When the input script line is encountered that defines
-style <I>equal</I> or <I>atom</I> that contain a formula is encountered, the
+a variable of style <I>equal</I> or <I>atom</I> that contains a formula, the
 formula is NOT immediately evaluated and the result stored.  See the
 discussion below about "Immediate Evaluation of Variables" if you want
 to do this.
@@ -724,10 +724,17 @@ produce only a global scalar or a per-atom vector, never both.
 </P>
 <P>There is a difference between referencing a variable with a leading $
 sign (e.g. $x or ${abc}) versus with a leading "v_" (e.g. v_x or
-v_abc).  The former can be used in any command, including a variable
+v_abc).  The former can be used in any input script command, including
-command, to force the immediate evaluation of the referenced variable
+a variable command.  The input script parser evaluates the reference
-and the substitution of its value into the command.  The latter is a
+variable immediately and substitutes its value into the command.  As
-required kind of argument to some commands (e.g. the <A HREF = "fix_ave_spatial.html">fix
+explained in <A HREF = "Section_commands.html#3_2">Section commands 3.2</A> for
+"Parsing rules", you can also use un-named "immediate" variables for
+this purpose.  An variable reference such as
+$((xlo+xhi)/2+sqrt(v_area)) evaluates the string between the
+parenthesis as an equal-style variable.
+</P>
+<P>Referencing a variable with a leading "v_" is an optional or required
+kind of argument for some commands (e.g. the <A HREF = "fix_ave_spatial.html">fix
 ave/spatial</A> or <A HREF = "dump.html">dump custom</A> or
 <A HREF = "thermo_style.html">thermo_style</A> commands) if you wish it to evaluate
 a variable periodically during a run.  It can also be used in a

doc/variable.txt

@@ -113,8 +113,8 @@ evaluation of the string.  Note that the same string can generate
 different values when it is evaluated at different times during a
 simulation.
 
-IMPORTANT NOTE: When the input script line that defines a variable of
+IMPORTANT NOTE: When the input script line is encountered that defines
-style {equal} or {atom} that contain a formula is encountered, the
+a variable of style {equal} or {atom} that contains a formula, the
 formula is NOT immediately evaluated and the result stored.  See the
 discussion below about "Immediate Evaluation of Variables" if you want
 to do this.
@@ -718,10 +718,17 @@ v_name\[I\]: atom I's value in per-atom vector :tb(s=:)
 
 There is a difference between referencing a variable with a leading $
 sign (e.g. $x or $\{abc\}) versus with a leading "v_" (e.g. v_x or
-v_abc).  The former can be used in any command, including a variable
+v_abc).  The former can be used in any input script command, including
-command, to force the immediate evaluation of the referenced variable
+a variable command.  The input script parser evaluates the reference
-and the substitution of its value into the command.  The latter is a
+variable immediately and substitutes its value into the command.  As
-required kind of argument to some commands (e.g. the "fix
+explained in "Section commands 3.2"_Section_commands.html#3_2 for
+"Parsing rules", you can also use un-named "immediate" variables for
+this purpose.  An variable reference such as
+$((xlo+xhi)/2+sqrt(v_area)) evaluates the string between the
+parenthesis as an equal-style variable.
+
+Referencing a variable with a leading "v_" is an optional or required
+kind of argument for some commands (e.g. the "fix
 ave/spatial"_fix_ave_spatial.html or "dump custom"_dump.html or
 "thermo_style"_thermo_style.html commands) if you wish it to evaluate
 a variable periodically during a run.  It can also be used in a