


  mcxi(1)                   USER COMMANDS                   mcxi(1)


  NAME
      mcx  -  a  stack  language  interpreter  for  interaction  with  the mcl
      libraries.

  SYNOPSIS
      mcxi (enter interactive mode)

      mcxi <mcxi expression>

  DESCRIPTION
      mcxi can be used both from the command line and interactively, and  sup-
      ports  a  rich  set of operations such as transposition, scaling, column
      scaling, multiplication, Hadamard powers and products, et cetera. It has
      variables,  control  primitives, and stack manipulation primitives.  The
      general aim is to support basic number and matrix arithmetic, as well as
      graph, set, and clustering operations. The language will be kept simple,
      and should serve only as a means of making the mcl framework a  pleasant
      one  for working with graphs, matrices, clusterings, and sets.  The lan-
      guage is typed, and currently  has  the  types  integer,  real,  matrix,
      string,  and  block.  Blocks are used both in control statements such as
      ifelse and while, and for defining compound statements resembling proce-
      dures  or functions.  Some of mcxi's primitives are overloaded. The fol-
      lowing is a very simple example of implementing and using  mcl  in  this
      language.


       2.0 .i def                   # define inflation value.
       /small lm                    # load matrix in file 'small'.
       dim id add                   # add identity matrix.
       st .x def                    # make stochastic, bind to x.
       { xpn .i infl vm } .mcl def  # define one mcl iteration.
       20 .x .mcl repeat            # iterate 20 times
       imac                         # interpret matrix as clustering.
       vm                           # view matrix (clustering).

      Somewhat  misleadingly,  '#'  is  not  recognized as a comment symbol by
      mcxi, so don't use it (yet).

      mcxi has quite a lot of primitives, and they are not  all  explained  in
      here.   However,  mcxi  has  several help facilities. mcxi's munge modes
      (command line, interactive, and file) are discussed first,  followed  by
      some syntactic and semantic rules.  Several groups of related primitives
      are then discussed. These are the help primitives help, grep,  ops,  and
      others, the binding primitives def, free, and unlink, the control primi-
      tives ifelse, do, repeat, and while, and the stack  manipulation  primi-
      tives pop, exch, dup, mdup, copy, roll, clear.  And for the record, mcxi
      has lt, lq, eq, gq, and gt.  In the grandiloquently named INDEX section,
      you find a list of all current mcxi primitives.

      First,  there  is  no difference as far as mcxi is concerned whether you
      give it a bunch of operators and  operands  directly  from  the  command
      line,  or  whether  you  do  it in interactive mode. Interactive mode is
      line-based; each time you type a carriage return, mcxi starts interpret-
      ing the line you typed. Newlines can be escaped by preceding them with a



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  mcxi(1)                   USER COMMANDS                   mcxi(1)


      backslash; mcxi will delay interpretation  and  keep  building  up  your
      expression.   Command line mode is the same as entering interactive mode
      and entering a single line. For non-batch processing,  interactive  mode
      is  the  safest, because mcxi will simply refuse to carry out impossible
      operations, whereas in command line mode it will exit.

      In interactive mode, mcxi will by default list the stack after each line
      you  type.  This  is verbosity level 1. There are four verbosity levels,
      namely 0, 1, 2, and 3 (in increasingly verbose  order).  Set  the  level
      with  the  vb primitive. Verbosity control is still a bit crude, this is
      one of the areas in which mcxi will be improved.

      There is another mcxi munge mode which is  entered  when  reading  files
      with  the  lf  (load  file)  primitive. This mode is not line-based, the
      whole file is interpreted in one go - there is  little  difference  with
      line-based mode. Beware though, it is currently not possible (nor neces-
      sary) to escape newlines in files.

      Currently, mcxi  parses  lines  of  text  into  atoms  in  an  extremely
      straightforward  way: Whitespace is the only separator, and it is always
      a separator. This has as a consequence that the block delimiters { and }
      are  not allowed to appear next to a non-white character. Another conse-
      quence is that strings cannot contain white spaces.  Both  these  condi-
      tions may be relaxed in the future though.

      Strings  are  always  entered  with a leading slash, and anything with a
      leading slash is a string, so /this is a string. Currently,  the  double
      quote  has no special meaning, but it may acquire meaning in the future,
      especially as in /"maybe the mcxi future will be brighter".

      Variables names are always entered with a leading dot, and anything with
      a  leading dot is a variable name. Variables are implicitly typed by the
      object to which they are bound. There is no support  for  arrays  (yet).
      If  variables are used, as in .x .y add, only the names of the variables
      are popped, and the binding between the names  and  their  values  stays
      intact.

      There  are  some  operators  that do in-place modification of the object
      that they act on, such as infl (inflation).  Currently,  these  are  all
      operators  acting  on  matrices. When presented with a variable, they do
      change the object associated with the variable.  In the  built-in  docu-
      mentation strings (accessible with help and grep), such in-place modifi-
      cation is denoted with a prime as in <m> -> <m'>.

      dup can be used to duplicate objects. In case of variables, this will be
      a copy of the variable name. If one occurrence is used to free the asso-
      ciated object by some operator, all  other  instances  of  the  variable
      become  stale.   mcxi  will  notice  this and you will see such elements
      marked as stale handles in the stack listing. copy can be used  to  copy
      the object associated with a variable.

      mcxi is/interprets a stack language. In order to add 1 and 2 you need to
      write 1 2 add. When add is evaluated, it removes the previous two  items
      from  the stack and replaces it with their sum, in this case the integer



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  mcxi(1)                   USER COMMANDS                   mcxi(1)


      3.  mcxi's types are denoted as <int>, <real>, <mx>, <str>, <block>, and
      so are objects that can be of that type. An object that is of underspec-
      ified type (such as taken by overloaded  operators)  is  denoted  <obj>.
      Where  a variable name must occur, <var> is written.  In mcxi parlance a
      'variable' is the same as 'handle'.  Remember that a variable named x is
      written .x, and that a string "foo" is entered as /foo in mcxi.

  OPERATORS
      help
        help  with  no arguments prints a descriptory line for each primitive.
        Can only be used at bottom of stack.  Alias: h.

      /str help
        help with argument /str prints a descriptive line  for  the  primitive
        named  str.  The  string must be identical to the primitive's name, or
        help will not show anything. Alias: h.

      /str grep
        Prints each descriptive line in which the string  str  occurs  (liter-
        ally).   So /matrix grep should produce a lot of matrix related primi-
        tives (although it may miss generic primitives such as add  and  mul).
        At bottom of stack, prints all descriptive lines.  Alias: g.

      ops
        Lists all primitives and aliases concisely in a paragraph.

      list
        Lists the contents of the operand stack.

      info
        Lists the top element of the operand stack.

      <int> tell
        Lists  the top <int> elements of the operand stack.  The trio of list,
        info, and tell is perhaps overdoing it slightly, but anyway  there  it
        is.

      vars
        Lists all variables currently bound.

      <obj> <var> def
        Bind <obj> to <var>. Redefinition is allowed.

      <var> free
        Break the binding between <var> and the object it currently binds, and
        remove object.

      unlink
        Break the binding between <var> and the object it currently binds, and
        push object on the stack.

      <int> <block1> <block2> ifelse
        If <int> is nonzero execute <block1>, otherwise execute <block2>.  The
        equate operators lt, lq, eq, gq, and gt can be used to leave an  <int>



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  mcxi(1)                   USER COMMANDS                   mcxi(1)


        on the stack.

      <block> do
        Execute <block> (one time).

      <int> <block> repeat
        Execute <block> <int> times.

      <block1> <block2> while
        This  primitive repeatedly executes the condition <block1>, which must
        push an integer each time it is executed. Each time, the pushed  inte-
        ger  is  popped. If it was non-zero, <block2> is executed, <block1> is
        executed, and the cycle continues. If it was zero, while is done.

      pop
        Pops one element off of the stack.

      exch
        Exchanges the top two elements of the stack.

      dup
        Duplicates the top element and pushes the duplicate onto the stack. In
        case  of  a  variable,  the  name  is duplicated and not the object it
        points to. In case of anonymous matrices  and  strings  (and  whatever
        other  (composite)  objects  may  emerge), a deep copy is made that is
        completely independent of the original object.

      <int> mdup
        Duplicates the top <int> elements. See the dup  entry  above  for  the
        semantics  of  duplication.  I wrote mdup because I thought some other
        operator needed it, which turned out to be false.  In the meantime,  I
        became  very  much  attached to mdup, so mail me if you think you have
        any useful use for it.

      copy
        Copies the top element and pushes the copy onto the stack.  In case of
        a variable, copies the object associated with the variable rather than
        the variable's name (as dup would do).

      <int1> <int2> roll
        Shift <int1> objects cyclically <int2> times to the right if <int2> is
        positive, to the left otherwise.

      clear
        Empty the stack. All objects bound to variables are unaffected.

  INDEX
      This  is  a  list of all mcxi's primitives, including aliases.  Do 'mcxi
      /<op> help' to see a short descriptive string, where <op> is one of  the
      primitives below (remember, strings need a leading slash).

      add addto cdim ch clear copy def dgt dim div do dup eq exch free gq grep
      gt hdm hdp help id ifelse imac infl info jj lf list lm lq  lt  max  mdup
      min mod mul ops pop pow quit rdim repeat roll st tell tp tut unlink vars



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  mcxi(1)                   USER COMMANDS                   mcxi(1)


      vb vm while wm xpn bye=quit d=def  f=free  h=help  i=info  l=list  p=pop
      g=grep u=unlink x=exch.

  AUTHOR
      Stijn van Dongen.

  SEE ALSO
      mclfamily(7)  for an overview of all the documentation and the utilities
      in the mcl family.
















































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