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author | Björn Gustavsson <[email protected]> | 2010-03-12 09:39:23 +0100 |
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committer | Björn Gustavsson <[email protected]> | 2010-06-02 11:51:25 +0200 |
commit | 7ac0808979534a94617c3391503c961d1ef72755 (patch) | |
tree | f929be0d00318569bef8d37ecf316512b17a1b19 /make/fakefop | |
parent | 1858cb81391d2bce29b4b7620574ca60128cebf7 (diff) | |
download | otp-7ac0808979534a94617c3391503c961d1ef72755.tar.gz otp-7ac0808979534a94617c3391503c961d1ef72755.tar.bz2 otp-7ac0808979534a94617c3391503c961d1ef72755.zip |
Evaluate element/2 at compile-time using type information
The erl_expand_records compiler pass translates the
following code:
h(X) when X#r1.a =:= 1 -> ok.
to (essentially):
h({r1,V1,V2}=X) when element(2, X) =:= 1 -> ok.
Since the guard can only be executed when the pattern matching
has succeeded, we know that the second element in the tuple X
must have been bound to V2. Thus we can eliminate the call
to element/2 like this:
h({r1,V1,V2}=X) when V1 =:= 1 -> ok.
Diffstat (limited to 'make/fakefop')
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