# Ada Language

This document describes the Ada bindings to the PLplot technical plotting software, how to obtain the necessary software components, and how to use them together.

## Overview

The Ada bindings for PLplot provide a way for Ada programmers to access the powerful PLplot technical plotting facilities directly from Ada programs while working completely in Ada; the Ada programmer never needs to know or worry that PLplot itself is written in another language.

There are a thin binding and two thick bindings provided. The thin binding presents the application programming interface (API) in a form very similar to the C API, although in 100% Ada. The thick bindings present the API in a form to which Ada programmers will be more accustomed and add some ease-of-use features. It is expected that the thick bindings will be preferred.

## The Bindings

The bindings are a re-expression and extension of the C-language API and as such are a kind of abstract layer between the user's code and the PLplot binary library. Additionally, there are a few capabilities not in the official API but nonetheless which are available to the C programmer which are included in the bindings and thus are directly available to the Ada programmer.

The thin binding is a layer between the thick bindings and the underlying C code. It is mainly a programming convenience for the developer of the bindings; this is a common implementation for foreign language bindings and for the most part, the user can ignore it.

There are two thick bindings provided for the convenience of the user. Either may be used and they both provide exactly the same functionality. The thick bindings are the user's main concern with programming for PLplot.

### Thin Binding

The thin binding, in the files `plplotthin.ads` and `plplotthin.adb`, is mostly a direct and obvious mapping of the C application programming interface (API) to Ada. Thus, for example, where a C program such as `plcol0` requires a single integer argument, there is a corresponding Ada program also called `plcol0` which also requires a single integer argument. (`plcol0` happens to set the drawing color using a number which is associated with a set of colors.) Various constants from the C API are also included here. Numeric types as defined in PLplot are associated with numeric types in Ada in the thin binding by use of Ada's type system. Thus, the thin binding refers to the PLplot-centric type `PLFLT` for floating-point types while the thick binding uses the usual Ada type `Long_Float`.

Many of the comments from the C source header file (similar in purpose to an Ada specification file) have been retained in the thin binding, even when they are no longer make sense. These might be pruned at some point to facilitate reading the Ada source.

Also included in the thin binding are some other declarations which help the Ada binding to mesh well with C by emulating certain data structures which are needed in some rather specialized usages as well as providing certain subprogram pointer types.

The Ada programmer working with either of the thick bindings will have to refer to the thin binding relatively rarely, if ever, and mainly to examine the subroutine pointer declarations and the several variant record types which are used mostly for contour and three-dimensional plots. However, some of these have been `subtype`-ed or `renames`-ed in the thick bindings so even less reference to the thin binding will be necessary. The goal is to put everything of interest to the user in the thick bindings and the user need not bother with the thin binding.

### The Thick Bindings

The thick bindings provide most of the information that the Ada programmer needs. Normally, only one of the two thick bindings would be used per user program but it should be possible to include both but that scenario would be unusual.

There are three main aspects of the thick bindings: providing an alternative access to the PLplot API, extending the PLplot functionality with some easy-to-use features, and overlaying Ada data structures and types.

In the first aspect, the thick bindings provide a fully Ada interface to the entire PLplot library. Packages are `with`-ed and `use`-d as normal Ada code. Ada arrays can be passed as usual, not requiring the array length or start or end indices to be passed separately. All necessary Ada types are made to match the underlying C types exactly.

The second aspect of the thick bindings is to provide some simplified ways to get a lot of plotting done with only one or two subroutine calls. For example, a single call to Simple_Plot can display from one to five "y's" as a function of a single "x" with default plot appearances chosen to suit many situations. Other simple plotters are available for three-dimensional and contour plots. Manipulating PLplot's colors is similarly made easy and some default color schemes are provided.

The third main aspect of the thick binding is to use Ada data structures and Ada's type system extensively to reduce the chances of inappropriate actions. For example, Ada arrays are used throughout (as opposed to C's pointer-plus-offset-while-carrying-along-the-size-separately approach). Quantities which have natural range limits are `subtype`-d to reflect those constraints. The hope is that program errors will result in more-familiar Ada compilation or run-time errors rather than error reports from the PLplot library or no reports at all. However, there remain a few instances where the typing could be improved and PLplot errors will still be reported from time to time.

Both the specification and body for the standard thick (and thin) binding contain the C subroutine name as a comment line immediately above the Ada procedure declaration; this should help in making the associations between "Ada" names and "PLplot" names. Also, the subroutine-specific comments from the C API have been retained verbatim.

### Standard Thick Binding Using Enhanced Names

The distinguishing feature of this thick binding (the "standard" binding) is to provide more descriptive names for PLplot subroutines, variables, constants, arguments, and other objects. Most Ada programmers will be more comfortable using these names. For example, in the C API as well as the thin Ada binding and the other thick Ada binding, the procedure `plcol0(1)` sets the drawing color to red. In the standard thick binding, the same thing is accomplished by writing `Set_Pen_Color(Red)`. The Ada program may just as well write `Set_Pen_Color(1)` since the binding merely sets a constant `Red` to be equal to the integer `1`. Many such numeric constants from the C API are given names in this thick binding. These renamed integers are discussed more fully in Section 7.2.

The disadvantage of this renaming is that it makes referring to the PLplot documentation somewhat awkward. There might be, at some time, a utility for easing this problem by providing an HTML file with links so that a "normal" PLplot name can be linked to the "Ada" name along with the appropriate entry in the Ada specification, as well as another HTML file with links from the "Ada" name directly to the PLplot web page that documents that name. It might also be possible to provide an alternate version of the documentation with the enhanced names used. (The developer of the bindings has a sed file prepared which makes most of the subroutine-name substitutions.) However, this thick binding retains the original C subprogram names as comments immediately above the function or procedure name in the code listing so it is relatively easy to locate the relevant item in the PLplot documentation.

One simple rule applies in reading the PLplot API documentation: the argument names are in the same order in Ada as in the PLplot documentation (the names are different) except that all array lengths are eliminated. The PLplot documentation, for each subroutine, shows a "redacted" version which should be correct for Ada as well as other languages which have proper arrays.

The standard bindings are in the Ada files `plplot.ads` and `plplot.adb`.

### Thick Binding Using Traditional Names

This thick binding provides exactly the same functionality as the standard thick binding but retains the original names as used in the C code and the PLplot documentation.

The traditional bindings are in the Ada files `plplot_traditional.ads` and `plplot_traditional.adb`.

## The Examples

An important part of the Ada bindings is the examples, some 33 of which demonstrate how to use many of the features of the PLplot package. These examples also serve as a test bed for the bindings in Ada and other languages by checking the Postscript files that are generated by each example against those generated by the C versions. These examples have been completely re-written in Ada (but retain a C flavor in the names that are given to objects). All of the Ada examples generate exactly the same Postscript as the C versions, Examples 14 and 17 excepted since those operate interactively and don't (normally) make Postscript. Two versions of each example are available, one calling the standard binding and the other the traditional binding. (In development, a sed script does almost all of the conversion automatically.)

## Obtaining the Software

There are three software components that you will need: an Ada compiler, the PLplot library, and the Ada bindings.

### Obtaining an Ada compiler

You will need an Ada compiler in order to use the Ada PLplot bindings. There are several compilers available. Here, we will focus on the free, open source compiler that is included with the GNU Compiler Collection, (gcc) which is at the center of much of the open source software movement. The gcc Ada compiler is known as GNAT, for GNU NYU Ada Translator, where NYU stands for New York University. (Although GNAT was originally developed at NYU, it has for many years been developed and supported commercially by AdaCore with academic and pro versions available.)

Your computer may already have GNAT installed, or you can download it from gcc.gnu.org. Another route to obtaining GNAT is from the AdaCore page, libre2.adacore.com. There are versions for many operating systems and processors including Apple's OS X or its open source version Darwin, Linux, and Windows. The gcc and AdaCore versions differ in their licenses. Download the version that you need and follow the installation instructions.

### Download and install PLplot

PLplot can be downloaded from the PLplot project page at sourceforge.net. Follow the installation instructions after downloading. The installation process requires that your computer has CMake installed. OS X users can try installing PLplot in its entirety from MacPorts. The advantage of using MacPorts is that all installation dependencies are automatically installed for you.

### The Ada bindings to PLplot

The third major software component is the bindings themselves; they are included with the PLplot software itself.

The bindings themselves are six Ada source files named (using GNAT filename extensions) `plplot.ads`, `plplot.adb`, `plplot_traditional.ads`, `plplot_traditional.adb`, `plplothin.ads`, and `plplotthin.adb`. There are two additional files, `plplot_auxiliary.ads` and `plplot_auxililary.adb` which will be discussed later, in Section 9.

## How to use the Ada bindings

### Ada 95 versus Ada 2005

The bindings will work for either Ada 95 or Ada 2005 but there is a slightly subtle point regarding the use and declaration of vectors and matrices. The package `PLplot_Auxiliary` declares the types

        type Real_Vector is array (Integer range <>) of Long_Float;
        type Real_Matrix is array (Integer range <>, Integer range <>) of Long_Float;

These declarations mimic exactly the declarations described in Annex G.3, Vector and Matrix Manipulation, of the Ada 2005 reference manual when the generic package therein described is specialized for `Long_Float`. The reason for this approach is to avoid requiring the user program to `with` `Ada.Numerics.Long_Real_Arrays` simply to gain access to these types and in the process require linking to the BLAS and LAPACK numerical libraries.

Ada 2005 introduced an annex G.3 which formally defines vector and matrix support to Ada, along with some common mathematical operations on those types. (This feature is a specific to vectors and matrices and extends the usual array apparatus.) The Ada PLplot user has a choice on how to deal with this. The default, as described in `PLplot_Auxiliary.ads`, has `Real_Vector` and `Real_Matrix` declared therein, separate from the Ada 2005 declarations. This allows the widest compatibility and does not require an Ada 2005 compiler. However, many users will want to gain the benefit of the built-in declarations of 2005. This is easily done: Read the short comments in `PLplot_Auxiliary.ads` on how to comment-out two lines and uncomment three lines. Either configuration will compile correctly, but depending on the Cmake configuration to expose a 2005 compiler in the later case. (Note that at some points in the documentation, Ada 2005 is referred to as Ada 2007, including some Cmake flags.)

This policy was changed in SVN version 11153. Before this, the type of compiler (Ada 95 or Ada 2005) had to be specified at the time that PLplot was built, and in the case of Ada 2005, the BLAS and LAPACK libraries had to be present and were subsequently linked.

### GNAT versus non-GNAT

The bindings were made using the GNAT compiler and there is a slight dependence on that compiler. Specifically, the `Unrestricted_Access` attribute of GNAT was used in making the function `Matrix_To_Pointers` in `plplotthin.adb` and in a few callbacks. `Matrix_To_Pointers` is called whenever an Ada matrix (2D array) is passed to a PLplot subroutine. For more about `Unrestricted_Access attribute`, see Implementation Defined Attributes in the GNAT Reference Manual. This dependency shouldn't be difficult to remove by either incorporating the GNAT code which implements it, by following the TO-DO comment near the function definition in `plplotthin.adb`, or by providing the proper aliasing.

Another GNAT dependency is used to parse command line arguments in a C-like way.

Pragma Warnings (Off, "some text") and Pragma Warnings (On, "some text") are used in the bindings to suppress warnings about a particular method used to interface with C code. These pragmas are also used in Ada Examples 21 to suppress a particular warning. Pragma Warnings is a GNAT extension. Non-GNAT usage could simply remove these pragmas with the resulting warnings ignored as they are benign.

Most of the GNAT dependencies can be found by searching the source code for "`GNAT`", "`Unrestricted_Access` and `Pragma Warnings`."

The GNAT dependence, though slight, will no doubt frustrate users of other Ada compilers. We welcome comments from those users, especially comments with specific suggestions on how to remove any GNAT-specific usages.

### Sample command line project

It is instructive to present a simple example that can be compiled and run from the command line. Although this example is specific to one installation, it should be fairly straightforward to adapt it to another installation. Toward that end, it is helpful to understand the PLplot lingo of "build directory" and "installation directory."

Here is a simple program that will generate a plot of part of a parabola.

     with
        PLplot_Auxiliary,
        PLplot;
     use
        PLplot_Auxiliary,
        PLplot;
     procedure Simple_Example is
        x, y : Real_Vector(-10 .. 10);
     begin
        for i in x'range loop
           x(i) := Long_Float(i);
           y(i) := x(i)**2;
        end loop;
        Initialize_PLplot; -- Call this only once.
        Simple_Plot(x, y); -- Make the plot.
        End_PLplot;        -- Call this only once.
     end Simple_Example;

Next is a bash script that will compile, bind, and link it. It is installation-specific in that paths to the GNAT compiler, PLplot libraries, and BLAS (Basic Linear Algebra System) and LAPACK (Linear Algebra Package) are hard-coded. You will have to adjust the paths to fit your installation. Some Linux installations which have GNAT 4.3 or later (Ada 2005) pre-installed might have already set the paths to the BLAS and LAPACK libraries.

(Note that the G.3 Annex of Ada 2005, in the GNAT version, depends heavily on BLAS and LAPACK. These packages are tried-and-true packages that are available from several places in either C or Fortran versions. The present example is specific to OS X which has both C and Fortran versions pre-installed.)

     #!/bin/bash
     /usr/local/ada-4.3/bin/gnatmake simple_example.adb \
     -aI/usr/local/plplot_build_dir/bindings/ada \
     -aL/usr/local/plplot_build_dir/bindings/ada/CMakeFiles/plplotadad.dir \
     -largs \
     /usr/local/plplot/lib/libplplotd.dylib \
     /Developer/SDKs/MacOSX10.4u.sdk/usr/lib/libblas.dylib \
     /Developer/SDKs/MacOSX10.4u.sdk/usr/lib/liblapack.dylib

The resulting binary program can be run by typing `./simple_example`

## Unique Features of the Ada bindings

The Ada bindings have been augmented with a number of features which are intended to simplify the use of PLplot. They include high-level features for simplified plotting (such as easy foreground-background control, a collection of "simple plotters," and easy color map manipulations), integer options which have been given meaningful names, and a few other focused additions. Many users will find that they can do most of their work using the "simple plotters".

### High-level features for simplified plotting

#### Foreground-background control

##### Draw_On_Black, Draw_On_White

The default for PLplot is to draw its graphics on a black background. A white background can be used instead with `Draw_On_White` or reset to the original mode with `Draw_On_Black`. Each of these manipulates color map 0 by swapping black and white so that e.g.with `Draw_On_White`, formerly white lines on a black background automatically become black lines on a white background.

#### Simple Plotters

Several high-level but flexible plotters are available and more might be added in the future. It is expected that many users will find that these high-level routines are adequate for most of their day-to-day plotting.

##### Multiplot_Pairs

Plot up to five x-y pairs with easy labelling, coloring, line width and styles, justification, and zooming.

##### Simple_Plot

Plot up to five y's against a single x with easy labelling and automatic line colors and styles.

##### Simple_Plot_Log_X

Same as `Simple_Plot` but with logarithmic x-axis.

##### Simple_Plot_Log_Y

Same as `Simple_Plot` but with logarithmic y-axis.

##### Simple_Plot_Log_XY

Same as `Simple_Plot` but with logarithmic x- and y-axes.

##### Simple_Plot_Pairs

Plot up to five x-y pairs with easy labelling and automatic line colors and styles.

##### Single_Plot

Plot a single x-y pair with flexible labels, axis styles, colors, line width and style, justification, and zooming.

##### Simple_Contour

Make a contour plot with labels

##### Simple_Mesh_3D

Easy 3D mesh plot with labels, zooming, and perspective controls

##### Simple_Surface_3D

Easy 3D surface plot with labels, zooming, and perspective controls

#### Simple color map manipulations

PLplot provides extensive manipulation and control of two separate color maps, color map 0 and color map 1. The Ada binding makes basic manipulations easier and also adds facilities for making snapshots of color map 0 so that any state of the map can easily be restored later. An initial snapshot is taken when the package is initialized so that the default color settings can always be restored after having been changed.

Another set of features lets the user reset the 16 individual colors in color map 0 after a color definition has been changed. It is important to note that while `Set_Pen_Color(Red)` (`plcol0` in the traditional binding) normally does what it says, `Red` simply has the value `1`. If the user changes the color map so that `1` corresponds to another color, then `Set_Pen_Color(Red)` will draw in that color instead of red. To always assure that red is drawn even if the color map has been changed for integer `1`, use `Set_Pen_Color(Reset_Red)` instead. These 16 "reset" functions return the appropriate default integer for the specified color but also reset that slot in the color table so that a subsequent call such as `Set_Pen_Color(Red)` will also cause drawing in red.

Color map 1 also gets a easy-to-use makeover for Ada users. There are several pre-built color themes that are useful for quickly making surface and mesh plots, `Color_Themes_For_Map_1_Type`. These color themes can be quickly applied with `Quick_Set_Color_Map_1`.

Miscellaneous other Ada features include a pre-built mask function for `Shade_Regions` that does no masking; perhaps the most useful purpose is to provide a template for writing mask functions that do mask. And there is a handy function for calculating the contour levels for making contour plots.

- Color table snapshots

  `Make_Snapshot_Of_Color_Map_0`

  `Restore_Snapshot_Of_Color_Map_0`

  `Restore_Default_Snapshot_Of_Color_Map_0`

- Color resetting functions for the 16 colors of color map 0

  `Reset_Black, Reset_Red, ..., Reset_White`

- Easy manipulation of color map 1

  Pre-built color themes for color map 1: `Color_Themes_For_Map_1_Type`

  Quick application of pre-built color themes: `Quick_Set_Color_Map_1`

- Other features

  A pre-built mask function for `Shade_Regions` that does no masking: `Mask_Function_No_Mask`

  An easy way to calculate an array of contour levels for contour plots: `Calculate_Contour_Levels`

### Integer Options Given Ada Names

The C version of PLplot uses a number of integers to mean specific things. Unfortunately, the meaning is lost when it it consigned to being a mere integer with no name. The Ada binding partially rectifies this situation by giving names to these integer constants. The integer can still be used if desired. (A more complete and safer rectification would use enumerated types.)

Below is a listing of at least the contexts in which these "re-namings" have been applied. In some cases the entire range of values is listed, but if there are more than about four such values for each context, only a sampling is given.

Instances

- Colors: Plot_Color_Type

  `0` is Black, `1` is Red, etc

- Justification for plots: `Justification_Type`

  `User_Justified`

  `Not_Justified`

  `Justified`

  `Justified_Square_Box`

- Axis styles: `Axis_Style_Type`

  `Linear_Major_Grid`

  `Linear_Minor_Grid`

  etc.

- Font styles: `Font_Style_Type`

  `Normal_Font`

  `Roman_Font`

  `Italic_Font`

  `Script_Font`

- Character sets: `Character_Set_Type`

  `Standard_Character_Set`

  `Extended_Character_Set`

- Plot orientation: `Orientation_Type`

  `Landscape`

  `Portrait`

- Modes for parsing command line arguments: `Parse_Mode_Type`

  E.g. `PL_PARSE_PARTIAL`

- Descriptions of map outlines (continents, states, etc.): `Map_Type`

  `Continents`

  `USA_and_States`

  `Continents_and_Countries`

  `USA_States_and_Continents`

- Various style and view options for 3D and surface plots

  E.g. `Lines_Parallel_To_X`

- Kind of gridding algorithm for interpolating 2D data to a grid: `Gridding_Algorithm_Type`

  E.g. `Grid_Bivariate_Cubic_Spline_Approximation`

- Flags for histogram style

  E.g. `Histogram_Default`

- Flags for histogram binning

  E.g. `Bin_Default`

- Names for color space models

  Hue, Lightness, Saturation: `HLS`

  Red, Green, Blue: `RGB`

### One-offs

To provide convenient string handling in a fashion that is familiar to Ada programmers, function versions which return a `String` type are provided of `Get_Device_Name`, `Get_Version_Number`, and `Get_Output_File_Name` (`plgdev`, `plgver`, and `plgfnam` in the traditional binding). These functions replace the procedure-style subprograms that are described in the C API documentation.

Overloaded `Set_Line_Style` (`plstyl` in the traditional binding) with a version that takes a single argument, `Default_Continuous_Line`. This replaces the awkward situation of calling the normal versions of these procedures with unused arguments simply to set the line style to the default, continuous, line.

The contour plotter `Contour_Plot_Irregular_Data` (`plfcont` in the traditional binding) is provided for making contour plots from irregularly spaced data. This feature is not documented in the PLplot API documentation.

The custom label function `Set_Custom_Label` (`plslabelfunc` in the traditional binding) can be called with null arguments to revert to using the default labelling scheme. Alternately, an Ada-only procedure with no arguments, `Use_Default_Labels`, is provided. See Ada example 19 (`x19a.adb` or `xthick19a.adb`) for a usage example.

The custom coordinate transform setter, `Set_Custom_Coordinate_Transform`, (`plstransform` in the traditional binding) can be called with null arguments to clear any previous custom coordinate transforms that the user has set, thus reverting to the default coordinate transform. Alternately, an Ada-only procedure with no arguments, `Clear_Custom_Coordinate_Transform`, is provided. See Ada example 19 (`x19a.adb` or `xthick19a.adb`) for a usage example.

The procedure `Set_Arrow_Style_For_Vector_Plots` (`plsvect` in the traditional binding) normally is called to define the shape of an arrow in vector plots. However, calling it with null pointer arguments (`System.Null_Address`) in place of the `Real_Vector` arrays and `False` for the `Fill_Arrow` argument causes the arrow shape to be reset to the default shape; this is implemented in Ada as an overloaded procedure in order to be consistent with the C API but is rather awkward. So there are two additional procedures that are added for the convenience of Ada programmers: Reset_Vector_Arrow_Style and plsvect, both without arguments, both available in both bindings, and the latter an overload of the normal arrow-setting procedure.

## Parts That Retain a C Flavor

There remains at least one area in the Ada bindings which is still affected by the C underpinnings. This might be cleaned up in future versions. There might be other residual C influence as well.

### Map-drawing

`plmapform` as called by `Draw_Latitude_Longitude` (`plmap`) and `Draw_Latitude_Longitude` (`plmeridians`)

This is the only place in the PLplot bindings where a C subprogram calls an Ada subprogram while passing an array. If the array is unconstrained, there is no guarantee that it will work because C has no way of telling Ada what offset to use for the beginning of the array. But passing a constrained array is acceptable with the downside that the array size must be fixed within the bindings as being large enough to handle any situation; currently, it is sized as `0 .. 2000`. See Example 19 for how this is handled in by the user program. The constrained array is called `Map_Form_Constrained_Array`.

## Known Variances

### Documentation

In numerous places in the documentation, a feature is listed or described as "C only." Many of these features are actually available in Ada. For example, in `Contour_Plot` (`plcont` in the traditional binding), the transformation from array indices to world coordinates is mentioned as "C only" but is actually available in Ada.

### API

The C documentation for `plscmap1l`, (`Set_Color_Map_1_Piecewise` in the thick binding) and `plscmap1la` (`Set_Color_Map_1_Piecewise_And_Alpha` in the thick binding) states that if the last argument is a null pointer, the behavior is as though a proper-length array of all `False` values was passed. In Ada, these procedures are overloaded to allow a last argument that can be either an array of Boolean or a value of the enumerated type `type Alt_Hue_Path_Type is (Alt_Hue_Path_None, Alt_Hue_Path_All)`.

## Compilation notes

### Ada 95 Versus Ada 2005

As discussed in Section 6.1, the bindings are made to work with Ada 95 and Ada 2005, but special steps need to be taken in order to access the numerical capabilities of Ada 2005 to the extent that vectors and arrays of the type defined in the Ada Reference Manual Annex G.3 are required to be passed to PLplot routines.

### GNAT Dependence

There is a slight but significant dependence on the GNAT version of Ada. This is discussed more fully in Section 6.2

### PLplot_Auxiliary

The bindings include files `PLplot_Auxiliary.ads` and `PLplot_Auxiliary.adb`. These files are currently used to provide a few convenience subprograms that are used in the examples. However, they are also associated with the above-mentioned facility to easily accommodate accessing the G.3 Annex vector-matrix manipulation facilities. If not for the desire for this easy "switching" ability, the `PLplot_Auxiliary` package could be removed from the `with` parts of the other binding files. Even so, it could be still removed with minor modifications to the `with` portions of the other binding files. But due to the other functions provided therein, they would still need to be referenced by most of the Ada examples.

## Notes for Apple Macintosh OS X users

The following comments apply to users of Apple Macintosh computers which run OS X. OS X users may use Apple's free integrated development environment (IDE) or may prefer other methods such as using a favorite editor and building from the command line.

OS X users should be aware that an excellent graphical terminal program is available and is highly recommended. It is called AquaTerm and is a full Cocoa program with window control. Performing a cut operation places a PDF of the front window on the clipboard, a convenience when working with other graphics or word processing programs.

### Using Apple's Xcode IDE

The Macintosh Ada community has made a plug-in for Apple's free Xcode integrated development environment (IDE) that makes programming Ada in Xcode possible. The plug-in is included with the compiler that is available at www.macada.org. Since Xcode is based on gcc, it is possible to work in the various gcc languages as well as to incorporate binaries such as the PLplot library.

In order to make an Xcode project, drag-and-drop source files and the PLplot library file to the Groups & Files pane of an Ada project. There are a few idiosyncrasies that you may encounter so make sure to contact the very friendly Macintosh Ada mailing list at www.macada.org or study the FAQ at that same site if you have any difficulties.

[This plug-in still works for some older versions of Xcode but not for newer versions, as of 2013.]

### AquaTerm

AquaTerm is a display option available on Macintosh computers using OS X and is supported by PLplot. It is a native Cocoa graphics "terminal" that is highly recommended. All output is antialiased and is easily cut-and-pasted in OS X's native PDF format. Get it here. It can also be installed from either the Fink or MacPorts projects.

### X11

Apple supplies the X11 windowing system that is popular on some other Unix and Linux operations systems. Formerly it was available as part of the Developer Tools but as of OS X 10.8 it is a separate installation. All PLplot programs made with the Ada bindings will run on X11. In fact, some types of interactivity such as Example 17 will not run on Apple's Terminal.app and should be run on X11 (or some other output device such as TCL/TK).

### GNAT for OS X

A web site for OS X users is at www.macada.org. Although rather dated, the mailing list is still active. Assistance can be found at other places on the web including the usenet comp.lang.ada.