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sav08:hoare_logic [2009/02/25 14:35] vkuncak |
sav08:hoare_logic [2009/02/25 14:46] vkuncak |
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| Hoare logic is a way of inserting annotations into code to make proofs about program behavior simpler. | Hoare logic is a way of inserting annotations into code to make proofs about program behavior simpler. | ||
| + | |||
| ===== Example Proof ===== | ===== Example Proof ===== | ||
| - | <code> | + | <code java> |
| - | {0 <= y} | + | //{0 <= y} |
| i = y; | i = y; | ||
| - | {0 <= y & i = y} | + | //{0 <= y & i = y} |
| r = 0; | r = 0; | ||
| - | {0 <= y & i = y & r = 0} | + | //{0 <= y & i = y & r = 0} |
| - | while {r = (y-i)*x & 0 <= i} | + | while //{r = (y-i)*x & 0 <= i} |
| (i > 0) ( | (i > 0) ( | ||
| - | {r = (y-i)*x & 0 < i} | + | //{r = (y-i)*x & 0 < i} |
| r = r + x; | r = r + x; | ||
| - | {r = (y-i+1)*x & 0 < i} | + | //{r = (y-i+1)*x & 0 < i} |
| i = i - 1 | i = i - 1 | ||
| - | {r = (y-i)*x & 0 <= i} | + | //{r = (y-i)*x & 0 <= i} |
| ) | ) | ||
| - | {r = x * y} | + | //{r = x * y} |
| </code> | </code> | ||