Test
Dynamic logic associates to every proposition an action called a test. When holds, the test acts as a NOP, changing nothing while allowing the action to move on. When is false, acts as BLOCK. Tests can be axiomatized as follows.
A8.
The corresponding theorem for is:
T8.
The construct if p then a else b is realized in dynamic logic as . This action expresses a guarded choice: if holds then is equivalent to, whereas is equivalent to BLOCK, and is equivalent to . Hence when is true the performer of the action can only take the left branch, and when is false the right.
The construct while p do a is realized as . This performs zero or more times and then performs . As long as remains true, the at the end blocks the performer from terminating the iteration prematurely, but as soon as it becomes false, further iterations of the body are blocked and the performer then has no choice but to exit via the test .
Read more about this topic: Dynamic Logic (modal Logic)
Famous quotes containing the word test:
“Our decision about energy will test the character of the American people and the ability of the President and the Congress to govern this nation. This difficult effort will be the “moral equivalent of war,” except that we will be uniting our efforts to build and not to destroy.”
—Jimmy Carter (James Earl Carter, Jr.)
“To answer a question so as to admit of no reply, is the test of a man.”
—Ralph Waldo Emerson (1803–1882)
“Unless the people can choose their leaders and rulers, and can revoke their choice at intervals long enough to test their measures by results, the government will be a tyranny exercised in the interests of whatever classes or castes or mobs or cliques have this choice.”
—George Bernard Shaw (1856–1950)