1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd">
<HTML
><HEAD
><TITLE
>Glue code</TITLE
><META
NAME="GENERATOR"
CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK
REL="HOME"
TITLE="The findlib User's Guide"
HREF="index.html"><LINK
REL="UP"
TITLE="Complex packages"
HREF="c278.html"><LINK
REL="PREVIOUS"
TITLE="Subpackages"
HREF="x338.html"><LINK
REL="NEXT"
TITLE="Plugins"
HREF="x352.html"></HEAD
><BODY
CLASS="SECT1"
BGCOLOR="#FFFFFF"
TEXT="#000000"
LINK="#0000FF"
VLINK="#840084"
ALINK="#0000FF"
><DIV
CLASS="NAVHEADER"
><TABLE
SUMMARY="Header navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TH
COLSPAN="3"
ALIGN="center"
>The findlib User's Guide</TH
></TR
><TR
><TD
WIDTH="10%"
ALIGN="left"
VALIGN="bottom"
><A
HREF="x338.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="80%"
ALIGN="center"
VALIGN="bottom"
>Chapter 5. Complex packages</TD
><TD
WIDTH="10%"
ALIGN="right"
VALIGN="bottom"
><A
HREF="x352.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="AEN345"
>Glue code</A
></H1
><P
>Imagine we have two packages p and q that are normally
independent, i.e. one can link p without q, and q without p. However,
when both p and q are used in the same program, it is expected that
they cooperate with each other. Of course, this situation can be
modeled with the help of subpackages (a real-world example of this are
p=lablgtk and q=lablgl).</P
><P
>The idea is as follows: p has a subpackage p.for_q that contains
code with special features for q, and q has a subpackage q.use_p that
depends on p, p.for_q, and q, and that contains the code using the
special features of p. Expressed in META files, p would define
<PRE
CLASS="PROGRAMLISTING"
># META file for p:
requires = "..."
archive = "..."
package "for_q" (
requires = "p"
archive = "..."
)</PRE
>
and q would define
<PRE
CLASS="PROGRAMLISTING"
># META file for q:
requires = "..."
archive = "..."
package "use_p" (
requires = "q,p.for_q"
archive = "..."
)</PRE
>
Of course, the program using both libraries must explicitly enable
the subpackages by mentioning "q.use_p" on the ocamlfind command line,
otherwise the glue code would be omitted.</P
><P
>Unfortunately, it is not possible to use the package predicates
pkg_p and pkg_q to add archives depending on whether the other
package is also selected. The problem is that the order cannot
be specified, i.e. whether p must be linked first or q.</P
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="x338.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="x352.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>Subpackages</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="c278.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>Plugins</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
|
