We incorporate strong negation in the theory of computable functionals TCF, a common extension of Plotkin's PCF and G\"{o}del's system $\mathbf{T}$, by defining simultaneously strong negation $A^{\mathbf{N}}$ of a formula $A$ and strong negation $P^{\mathbf{N}}$ of a predicate $P$ in TCF. As a special case of the latter, we get strong negation of an inductive and a coinductive predicate of TCF. We prove appropriate versions of the Ex falso quodlibet and of double negation elimination for strong negation in TCF. We introduce the so-called tight formulas of TCF i.e., formulas implied from the weak negation of their strong negation, and the relative tight formulas. We present various case-studies and examples, which reveal the naturality of our definition of strong negation in TCF and justify the use of TCF as a formal system for a large part of Bishop-style constructive mathematics.
翻译:我们在可计算泛函理论TCF(Plotkin的PCF与Gödel系统$\mathbf{T}$的常见扩展)中引入强否定,通过同时定义TCF中公式$A$的强否定$A^{\mathbf{N}}$与谓词$P$的强否定$P^{\mathbf{N}}$来实现。作为后者的特例,我们得到了TCF中归纳谓词与余归纳谓词的强否定。我们证明了TCF中强否定对应的Ex falso quodlibet原理及双重否定消去原理的适当形式。我们引入了TCF中的紧致公式(即从其强否定的弱否定可推出的公式)以及相对紧致公式。通过多个案例研究与示例,我们揭示了TCF中强否定定义的自然性,并论证了TCF可作为Bishop风格构造性数学大部分内容的形式系统。