43 lines
1.7 KiB
C
43 lines
1.7 KiB
C
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#include <stdio.h>
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#define Result_t(T, E) \
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struct Result_##T##_##E { \
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bool is_ok; \
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union { \
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T value; \
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E error; \
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}; \
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}
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#define Ok(T, E) \
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(struct Result_##T##_##E) { \
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.is_ok = true, .value = (T)_OK_IMPL
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#define _OK_IMPL(...) \
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__VA_ARGS__ \
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}
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#define Err(T, E) \
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(struct Result_##T##_##E) { \
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.is_ok = false, .error = (E)_ERR_IMPL
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#define _ERR_IMPL(...) \
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__VA_ARGS__ \
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}
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typedef const char *ErrorMessage_t;
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Result_t(int, ErrorMessage_t) my_func(int i) {
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if (i == 42)
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return Ok(int, ErrorMessage_t)(100);
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else
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return Err(int, ErrorMessage_t)("Cannot do the thing");
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}
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int main(void) {
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Result_t(int, ErrorMessage_t) x = my_func(42);
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if (x.is_ok) {
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printf("%d\n", x.value);
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} else {
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printf("%s\n", x.error);
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}
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}
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