encounter error while it is installing opam with macport

[心如烛光]

Hi,everybody!
    I wanna install opam for my MacBook Pro (osx10.8.5 mountainlion) with macport. Unfortunately,I get error while it is installing.How could I fix it?Thank you for your help!
yours!
here is the message comes from terminal:
$ sudo port install opam
--->  Computing dependencies for opam
--->  Dependencies to be installed: aspcud gringo re2c scons
--->  Verifying checksums for re2c
Error: org.macports.checksum for port re2c returned: re2c-0.14.3.tar.gz does not exist in /opt/local/var/macports/distfiles/re2c
Error: Failed to install re2c
Please see the log file for port re2c for details:
    /opt/local/var/macports/logs/_opt_local_var_macports_sources_rsync.macports.org_release_tarballs_ports_devel_re2c/re2c/main.log
Error: The following dependencies were not installed: aspcud gringo re2c scons
To report a bug, follow the instructions in the guide:
    http://guide.macports.org/#project.tickets
Error: Processing of port opam failed
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