+assert_version (required, 'gcc', '2.8', 'GNU C compiler', 'gcc')
+assert_version (required, 'g++', '3.0.5', 'GNU C++ compiler', 'g++')
+assert_version (required, 'python', '2.1', 'Python (www.python.org)', 'python')
+assert_version (required, 'guile-config', '1.6', 'GUILE development',
+ 'libguile-dev or guile-devel')
+# Do not use bison 1.50 and 1.75.
+assert_version (required, 'bison', '1.25', 'Bison -- parser generator',
+ 'bison')
+assert_version (required, 'flex', '0.0', 'Flex -- lexer generator', 'flex')
+
+
+optional = []
+assert_version (optional, 'makeinfo', '4.7', 'Makeinfo tool', 'texinfo')
+assert_version (optional, 'guile', '1.6', 'GUILE scheme',
+ 'libguile-dev or guile-devel')
+assert_version (optional, 'mftrace', '1.0.27', 'Metafont tracing Type1',
+ 'mftrace')
+assert_version (optional, 'perl', '4.0',
+ 'Perl practical efficient readonly language', 'perl')