$ brew install R outpu

~/Desktop% brew install -v R
==> Downloading http://cran.r-project.org/src/base/R-2/R-2.15.0.tar.gz
Already downloaded: /Library/Caches/Homebrew/r-2.15.0.tar.gz
/usr/bin/tar xf /Library/Caches/Homebrew/r-2.15.0.tar.gz
==> Using Homebrew-provided fortran compiler.
This may be changed by setting the FC environment variable.

==> ./configure --prefix=/usr/local/Cellar/r/2.15.0 --with-aqua --enable-R-framework --with-lapack
./configure --prefix=/usr/local/Cellar/r/2.15.0 --with-aqua --enable-R-framework --with-lapack
checking build system type... x86_64-apple-darwin11.4.0
checking host system type... x86_64-apple-darwin11.4.0
loading site script './config.site'
loading build-specific script './config.site'
checking for pwd... /bin/pwd
checking whether builddir is srcdir... yes
checking for working aclocal... found
checking for working autoconf... found
checking for working automake... found
checking for working autoheader... found
checking for gawk... no
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checking for awk... awk
checking whether ln -s works... yes
checking for bison... bison -y
checking for ar... ar
checking for a BSD-compatible install... /usr/bin/install -c
checking for sed... /usr/bin/sed
checking for which... /usr/bin/which
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checking for texi2dvi... /usr/bin/texi2dvi
checking for kpsewhich... /usr/texbin/kpsewhich
configure: WARNING: inconsolata.sty not found: PDF vignettes and package manuals will not be rendered optimally
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using default browser ... /usr/bin/open
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checking for gcc... /usr/bin/clang
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
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checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether /usr/bin/clang accepts -g... yes
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checking how to run the C preprocessor... /usr/bin/clang -E
checking for grep that handles long lines and -e... /usr/bin/grep
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checking whether /usr/bin/clang needs -traditional... no
checking how to run the C preprocessor... /usr/bin/clang -E
defining F77 to be /usr/local/bin/gfortran
checking whether we are using the GNU Fortran 77 compiler... no
checking whether /usr/local/bin/gfortran accepts -g... yes
checking whether we are using the GNU C++ compiler... yes
checking whether /usr/bin/clang++ accepts -g... yes
checking how to run the C++ preprocessor... /usr/bin/clang++ -E
checking whether __attribute__((visibility())) is supported... no
checking whether /usr/bin/clang accepts -fvisibility... yes
checking whether /usr/local/bin/gfortran accepts -fvisibility... no
checking for ANSI C header files... yes
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checking minix/config.h usability... no
checking minix/config.h presence... no
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checking whether it is safe to define __EXTENSIONS__... yes
checking whether we are using the GNU Objective C compiler... yes
checking whether /usr/bin/clang accepts -g... yes
checking for Objective C++ compiler... trying some possibilities
checking whether /usr/bin/clang++ can compile ObjC++... yes
/usr/bin/clang++
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checking for fgrep... /usr/bin/grep -F
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checking if the linker (/usr/bin/clang) is GNU ld... no
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checking the name lister (/usr/bin/nm) interface... BSD nm
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checking how to recognize dependent libraries... pass_all
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checking command to parse /usr/bin/nm output from /usr/bin/clang object... ok
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checking whether we are using the GNU Fortran 77 compiler... (cached) no
checking whether /usr/local/bin/gfortran accepts -g... (cached) yes
checking for objdir... .libs
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checking if /usr/bin/clang supports -c -o file.o... yes
checking if /usr/bin/clang supports -c -o file.o... (cached) yes
checking whether the /usr/bin/clang linker (/usr/bin/clang) supports shared libraries... yes
checking dynamic linker characteristics... darwin11.4.0 dyld
checking how to hardcode library paths into programs... immediate
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checking whether the /usr/bin/clang++ linker (/usr/bin/clang) supports shared libraries... yes
checking dynamic linker characteristics... darwin11.4.0 dyld
checking how to hardcode library paths into programs... immediate
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checking whether the /usr/local/bin/gfortran linker (/usr/bin/clang) supports shared libraries... no
checking dynamic linker characteristics... darwin11.4.0 dyld
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checking for rl_callback_read_char in -lreadline... yes
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checking for library containing opendir... none required
checking for sys/wait.h that is POSIX.1 compatible... yes
checking arpa/inet.h usability... yes
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checking netdb.h usability... yes
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checking whether setjmp.h is POSIX.1 compatible... yes
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checking return type of signal handlers... void
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checking for /usr/bin/clang option to accept ISO C99... none needed
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checking for inline... inline
checking size of int... 4
checking size of long... 8
checking size of long long... 8
checking size of double... 8
checking size of long double... 16
checking size of size_t... 8
checking whether we can compute C Make dependencies... yes, using /usr/bin/clang -MM
checking whether /usr/bin/clang supports -c -o FILE.lo... yes
checking for /usr/bin/clang option to support OpenMP... unsupported
checking how to get verbose linking output from /usr/local/bin/gfortran... configure: WARNING: compilation failed

checking for Fortran 77 libraries of /usr/local/bin/gfortran... 
checking how to get verbose linking output from /usr/bin/clang... -v
checking for C libraries of /usr/bin/clang...  -lcrt1.10.6.o -L/usr/local/Cellar/readline/6.2.2/lib -L/usr/X11/lib -lSystem /usr/bin/../lib/clang/3.1/lib/darwin/libclang_rt.osx.a
checking for dummy main to link with Fortran 77 libraries... none
checking for Fortran 77 name-mangling scheme... configure: error: in `/private/tmp/homebrew-r-2.15.0-Drsz/R-2.15.0':
configure: error: cannot compile a simple Fortran program
See `config.log' for more details
config.log was copied to /Users/vladi/Library/Logs/Homebrew
==> Exit Status: 1
https://github.com/mxcl/master/blob/master/Library/Formula/r.rb#L44
==> Build Environment
CPU: dual-core 64-bit penryn
MacOS: 10.7.4-x86_64
Xcode: 4.3.2
CC: /usr/bin/clang
CXX: /usr/bin/clang++ => /usr/bin/clang
LD: /usr/bin/clang
CFLAGS: -Os -w -pipe -march=native -Qunused-arguments
CXXFLAGS: -Os -w -pipe -march=native -Qunused-arguments
CPPFLAGS: -I/usr/local/Cellar/readline/6.2.2/include -I/usr/X11/include
LDFLAGS: -L/usr/local/Cellar/readline/6.2.2/lib -L/usr/X11/lib
MAKEFLAGS: -j2
Error: Failed executing: ./configure --prefix=/usr/local/Cellar/r/2.15.0 --with-aqua --enable-R-framework --with-lapack (r.rb:44)
These existing issues may help you:
    https://github.com/mxcl/homebrew/issues/9845
    https://github.com/mxcl/homebrew/issues/12623
Otherwise, please report the bug:
    https://github.com/mxcl/homebrew/wiki/reporting-bugs
We saved the configure log, please gist it if you report the issue:
    ~/Library/Logs/Homebrew/config.log