The recursion hierarchy for PCF is strict
The recursion hierarchy for PCF is strict
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PCF 的递归层次结构很严格
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
J. Longley
中科院分区：
文献类型：
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作者：
J. Longley
Let PCFk denote the sublanguage of Plotkin’s PCF in which xed point operators Y are admitted only for types of level k. We show that the languages PCFk form a strict hierarchy, in the sense that for each k, there are closed programs of PCFk+1 that are not observationally equivalent to any programs of PCFk. This answers a question posed by Berger in 1999. Our proof makes substantial use of the theory of nested
