Matrix Elements VB-800 Manuel d'utilisateur télécharger pdf (Page 19)

A1.5 Adding a user-friendly interface with Visual C

print(vscore);

}

.......................................................................................

A mistake in the callback function is handled in the same way as other Ox errors.

For example, when changing vP[1] to vP[3] in dRosenbrock:

Runtime error: ’[3] in matrix[1][2]’ index out of range

Runtime error occurred in dRosenbrock(16), call trace:

C:\ox\dev\windows\callback\callback.ox (16): dRosenbrock

Runtime error: in callback function

Runtime error occurred in main(29), call trace:

C:\ox\dev\windows\callback\callback.ox (29): main

A1.5 Adding a user-friendly interface with Visual C

Ox is limited in terms of user interaction, only providing console style input using the

scan function. It is possible, however, to use much more powerful external tools to

add dialogs and menus. In that way, a much better interface could be written than ever

possible directly in Ox. Indeed, there are no plans to make interface components an

intrinsic part of Ox: this would always lag behind the latest developments.

Various approaches could be considered to add a user interface:

(1) Write a separate program which creates an input ﬁle.

(2) Write a separate program which generates an Ox source ﬁle.

(3) Write a DLL which exports dialogs to be used in Ox source code.

(4) Call Ox source code from an interactive program.

The ﬁrst two approaches are the most simple, and can be used if the code is ‘uni-

directional’ (i.e. input is collected, then the program is run). Approach (2) is taken

by PcNaive: it collects user input on Monte Carlo design, generates an Ox program

from this, and calls OxRun to run the generated code. It can also retrieve settings from

previously generated source code, to produce a sophisticated interactive package.

The remaining two approaches are more appropriate if the program must be truly

interactive, or when further interaction is based on the result of computations. Examples

in the next two sections use method (4). An application called RanApp is developed.

This offers a set of actions and a dialog to change settings. Each action results in an Ox

function being called. It is RanApp which is in control of the Ox run-time system; in

method (3) that would be the other way round.

The examples below use Visual C

and Visual Basic (§A1.6). Java could also be

considered. A key requirement is that the tool can make calls to C functions residing in

the Ox DLL.

The knowledge from the previous sections already sufﬁces to write an interface us-

ing FOxCallBack. There is, however, a second form of simpliﬁed callbacks which calls

a function by its text name. This method does not allow for arguments, and bypasses

the main function. The RanApp example in this section uses the simpliﬁed method,

and adds additional functions to be called from Ox to get dialog driven input.

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Matrix Elements VB-800 Manuel d'utilisateur Page 19

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