Chapters: 1: Introduction 2: Simple example 3: Invocation 4: Finer Control 5: X-Y Plots 6: Contour Plots 7: Image Plots 8: Examples 9: Gri Commands 10: Programming 11: Environment 12: Emacs Mode 13: History 14: Installation 15: Gri Bugs 16: Test Suite 17: Gri in Press 18: Acknowledgments 19: License Indices: Concepts Commands Variables | ## 9.2: Command syntax The syntax description is enclosed within angled single quotes, optional items are enclosed in square brackets, multiword items are enclosed in curly braces, and vertical bars separate different legitimate choices. For example, the documentation item for the command for drawing contours
    `draw contour \
        [.value. |  \
          {.min. .max. .inc. [.inc_unlabelled.]}] \
        [unlabelled]'
indicates that following are legal:
    draw contour                   # gri selects levels
    draw contour unlabelled        # " but unlabelled
    draw contour 10                # single contour line
    draw contour 10 unlabelled     # " but unlabelled
    draw contour 0 100 10          # contours at z=0,1,
    draw contour 0 10 1 unlabelled # " but unlabelled
    # contours at 0, 0.1, ... labelled at 0, 1
    draw contour 0 10 1 0.1
Note that items enclosed in braces must appear in their entirety; for example,
    draw contour 0 10              # WRONG; missing .inc.
which might look similar ``draw contour .min. .max. .inc.`' to you, looks like garbage to Gri. Gri will recognize it as an attempt at the ``draw contour`' command (because the first 2 words match the syntax) but it will then get confused, spit out an error message, and quit.