Metadata-Version: 1.0
Name: cnd
Version: 2011.3
Summary: A preprocessor that gives C multidimensional arrays
Home-page: http://mathema.tician.de/software/cnd
Author: Andreas Kloeckner
Author-email: inform@tiker.net
License: MIT
Description: CnD is a source-to-source translator that makes using n-dimensional arrays
        in C more pleasant.  It will turn this code::
        
            void sgemm(float *a, float *b, float *c, int n)
            {
              dimension "fortran" a[n; n];
              dimension "fortran" b[n; n];
              dimension c[n; n];
        
              for (int i = 1; i <= n; ++i)
                for (int j = 1; j <= n; ++j)
                {
                  float tmp = 0;
        
                  for (int k = 1; k <= n; ++k)
                    tmp += a[i;k]*b[k;j];
        
                  c[i-1;j-1] = tmp;
                }
            }
        
        into this::
        
            void sgemm(float *a, float *b, float *c, int n)
            {
              for (int i = 1; i <= n; ++i)
                for (int j = 1; j <= n; ++j)
              {
                float tmp = 0;
                for (int k = 1; k <= n; ++k)
                  tmp += a[((k - 1) * ((n - 1) + 1)) + (i - 1)] * b[((j - 1) * ((n - 1) + 1)) + (k - 1)];
        
                c[((i - 1) * n) + (j - 1)] = tmp;
              }
            }
        
        You may also take a look at a `more comprehensive example
        <https://github.com/inducer/cnd/blob/master/examples/basic.c>`_
        that shows a few extra bells and whistles.
        
        The only effect of a `dimension` declaration is to modify the interpretation of
        the `array(idx)` subscript operator. `dimension` declarations obey regular C
        scoping rules.  Note that in order to prevent hard-to-find bugs,
        multi-dimensional array references using square brackets are considered an
        error.
        
        I'd also like to note that CnD is a robust, parser-based translator, not a flaky
        text replacement tool.  It understands all of C99.
        
        Each axis specification in a `dimension` declaration has the following form::
        
            start:end:stride:leading_dimension
        
        `start` may be omitted. `end` and `stride` may also be omitted, but if entries
        after them are to be specified, their trailing colons must remain in place. For
        example, the axis specification `:5` simply specifies a stride of 5. The stride
        simply acts as a multiplier on the index.  No plausibility checking whatsoever
        is done on the dimension declaration.  You may shoot yourself in the foot any way
        you like.
        
        If the layout is given as `"c"` or not given at all, the following things are true:
        
        * The array is laid out in row-major order.
        * The `end` index is taken to be exclusive, if specified.
        * The `start` index defaults to 0.
        
        If the layout is given as `"fortran"`, the following things are true:
        
        * The array is laid out in column-major order.
        * The `end` index is taken to be inclusive, if specified.
        * The `start` index defaults to 1.
        
        (Most) of the knowledge contained in the `dimension` declaration may be reobtained
        programmatically by the follwing functions:
        
        * `rankof(a)`
        * `nitemsof(a)`
        * `lboundof(a, axis)`
        * `uboundof(a, axis)` (returns the user-specified upper bound)
        * `puboundof(a, axis)` (returns the index just past the end of axis)
        * `ldimof(a, axis)`
        * `strideof(a, axis)`
        
        In each case, `axis` must be a constant integer (not a constant expression, a
        plain integer).
        
        Installation / Usage
        --------------------
        
        You may obtain CnD by downloading the tarball from the `package index
        <http://pypi.python.org/pypi/cnd>`_, or from `github
        <http://github.com/inducer/cnd>`_::
        
            $ git clone git://github.com/inducer/cnd.git
            $ cd cnd
            $ git submodule init
            $ git submodule update
        
        To use CnD, simply add `distribution-dir/bin` to your `PATH`.
        
        To get started, simply run (from within the `cnd` root)::
        
            $ cd examples
            $ ../bin/cndcc gcc -std=c99 basic.c
            $ ./a.out
        
        If you would like more fine-grained control over the translation process, the
        `cnd` command exposes just the source-to-source translation.  Note that `cnd`
        expects preprocessed source. You may pass the option `-E` to have `cnd` run the
        preprocessor on your source for you. Run::
        
            $ cnd -h
        
        to get full help on the command line interface. You may set the `CND_CPP`
        environment variable to the preprocessor you wish to use.
        
        FAQ
        ---
        
        Semicolons (not commas) to separate indices? Are you kidding me?
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        
        No. Turns out our hand is forced in this matter by a curious interaction with
        the C preprocessor. Consider the following stiuation::
        
            #define MY_MACRO(a) /* something rather */
        
            MY_MACRO(array[i,j])
        
        The preprocessor sees the comma and rips our array access apart into two macro
        arguments, and then complains that `MY_MACRO` takes only one argument.  Not
        very smart, but such is life. Thus round parentheses are the only choice--and
        the `dimension` declaration (where there would be a choice) uses parentheses to
        match the array access syntax.
        
        (Credit for discovering this goes to Zydrunas Gimbutas.)
        
        After discovering the above fact, we went through a number of choices for the syntax.
        First, we tried::
        
            a(i,j)
        
        While this was fine technically (and Fortran-compatible), it felt decidedly out
        of place in a C program, to the point of making the code hard to decipher.
        
        We also considered::
        
            a[i][j]
        
        but this seemed wordy and deemphasized the fact that this was not 'classic' C-style
        array lookup.
        
        But Vim highlights semicolons as an error!
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        
        Good point. Add this line::
        
            let g:c_no_bracket_error = 1
        
        to your `.vimrc`.
        
        Version History
        ---------------
        
        2011.3
        ^^^^^^
        
        * Syntax change from `a(i,j)` to `a[i;j]`.
        * Parser support for many more GNU extensions, `tgmath.h`
          now works on OS X (10.7) and Linux.
        
        2011.2
        ^^^^^^
        
        * Syntax change from `a[i,j]` to `a(i,j)`.
        * Fixes for OS X and two bugs.
        * Generate #line directives.
        
        2011.1
        ^^^^^^
        
        Initial release.
        
        Future Features
        ^^^^^^^^^^^^^^^
        
        * Caching of lexer/parser tables (faster startup)
        * Bounds checking.
        
        Author
        ------
        
        Andreas Kloeckner <inform@tiker.net>, based on discussions with Zydrunas Gimbutas.
        
Platform: UNKNOWN
