core: Add option::unwrap
This function uses some unsafe code to move the value out of an option.
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@ -84,6 +84,57 @@ fn may<T>(opt: t<T>, f: fn(T)) {
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alt opt { none {/* nothing */ } some(t) { f(t); } }
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alt opt { none {/* nothing */ } some(t) { f(t); } }
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}
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}
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/*
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Function: unwrap
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Moves a value out of an option type and returns it. Useful primarily
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for getting strings, vectors and unique pointers out of option types
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without copying them.
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*/
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fn unwrap<T>(-opt: t<T>) -> T unsafe {
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let addr = alt opt {
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some(x) { ptr::addr_of(x) }
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none { fail "option none" }
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};
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let liberated_value = unsafe::reinterpret_cast(*addr);
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unsafe::leak(opt);
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ret liberated_value;
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}
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#[test]
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fn test_unwrap_ptr() {
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let x = ~0;
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let addr_x = ptr::addr_of(*x);
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let opt = some(x);
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let y = unwrap(opt);
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let addr_y = ptr::addr_of(*y);
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assert addr_x == addr_y;
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}
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#[test]
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fn test_unwrap_str() {
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let x = "test";
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let addr_x = str::as_buf(x) {|buf| ptr::addr_of(buf) };
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let opt = some(x);
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let y = unwrap(opt);
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let addr_y = str::as_buf(y) {|buf| ptr::addr_of(buf) };
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assert addr_x == addr_y;
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}
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#[test]
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fn test_unwrap_resource() {
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resource r(i: @mutable int) {
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*i += 1;
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}
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let i = @mutable 0;
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{
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let x = r(i);
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let opt = some(x);
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let y = unwrap(opt);
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}
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assert *i == 1;
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}
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// Local Variables:
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// Local Variables:
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// mode: rust;
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// mode: rust;
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// fill-column: 78;
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// fill-column: 78;
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