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
      supports 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
      language 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
      procedures or functions.  Some of mcxi's primitives are overloaded. The
      following 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
      primitives ifelse, do, repeat, and while, and the stack manipulation
      primitives 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
      interpreting the line you typed. Newlines can be escaped by preceding
      them with a 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
      necessary) 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
      consequence is that strings cannot contain white spaces. Both these
      conditions 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
      documentation strings (accessible with help and grep), such in-place
      modification 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
      associated 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
      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
      underspecified 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
        (literally).  So /matrix grep should produce a lot of matrix related
        primitives (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>
        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
        integer 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
      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.



  mcxi 1.008, 09-308                4 Nov 2009                           mcxi(1)
