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Calculational Reasoning Revisited  An Isabelle/Isar experience
 THEOREM PROVING IN HIGHER ORDER LOGICS: TPHOLS 2001
, 2001
"... We discuss the general concept of calculational reasoning within Isabelle/Isar, which provides a framework for highlevel natural deduction proofs that may be written in a humanreadable fashion. Setting out from a few basic logical concepts of the underlying metalogical framework of Isabelle, such ..."
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We discuss the general concept of calculational reasoning within Isabelle/Isar, which provides a framework for highlevel natural deduction proofs that may be written in a humanreadable fashion. Setting out from a few basic logical concepts of the underlying metalogical framework of Isabelle, such as higherorder unification and resolution, calculational commands are added to the basic Isar proof language in a flexible and nonintrusive manner. Thus calculational proof style may be combined with the remaining natural deduction proof language in a liberal manner, resulting in many useful proof patterns. A casestudy on formalizing Computational Tree Logic (CTL) in simplytyped settheory demonstrates common calculational idioms in practice.
Mizar Light for HOL Light
 Theorem Proving in Higher Order Logics: TPHOLs 2001, LNCS 2152
, 2001
"... There are two dierent approaches to formalizing proofs in a computer: the procedural approach (which is the one of the HOL system) and the declarative approach (which is the one of the Mizar system). ..."
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Cited by 11 (3 self)
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There are two dierent approaches to formalizing proofs in a computer: the procedural approach (which is the one of the HOL system) and the declarative approach (which is the one of the Mizar system).
A Comparison of the Mathematical Proof Languages Mizar and Isar
 Journal of Automated Reasoning
, 2002
"... The mathematical proof checker Mizar by Andrzej Trybulec uses a proof input language that is much more readable than the input languages of most other proof assistants. This system also di#ers in many other respects from most current systems. John Harrison has shown that one can have a Mizar mode on ..."
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Cited by 10 (3 self)
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The mathematical proof checker Mizar by Andrzej Trybulec uses a proof input language that is much more readable than the input languages of most other proof assistants. This system also di#ers in many other respects from most current systems. John Harrison has shown that one can have a Mizar mode on top of a tactical prover, allowing one to combine a mathematical proof language with other styles of proof checking. Currently the only fully developed Mizar mode in this style is the Isar proof language for the Isabelle theorem prover. In fact the Isar language has become the o#cial input language to the Isabelle system, even though many users still use its lowlevel tactical part only.
A Comparison of Mizar and Isar
 J. Automated Reasoning
, 2002
"... Abstract. The mathematical proof checker Mizar by Andrzej Trybulec uses a proof input language that is much more readable than the input languages of most other proof assistants. This system also differs in many other respects from most current systems. John Harrison has shown that one can have a Mi ..."
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Cited by 8 (0 self)
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Abstract. The mathematical proof checker Mizar by Andrzej Trybulec uses a proof input language that is much more readable than the input languages of most other proof assistants. This system also differs in many other respects from most current systems. John Harrison has shown that one can have a Mizar mode on top of a tactical prover, allowing one to combine a mathematical proof language with other styles of proof checking. Currently the only fully developed Mizar mode in this style is the Isar proof language for the Isabelle theorem prover. In fact the Isar language has become the official input language to the Isabelle system, even though many users still use its lowlevel tactical part only. In this paper we compare Mizar and Isar. A small example, Euclid’s proof of the existence of infinitely many primes, is shown in both systems. We also include slightly higherlevel views of formal proof sketches. Moreover a list of differences between Mizar and Isar is presented, highlighting the strengths of both systems from the perspective of endusers. Finally, we point out some key differences of the
A DEFENCE OF MATHEMATICAL PLURALISM
, 2004
"... We approach the philosophy of mathematics via a discussion of the differences between classical mathematics and constructive mathematics, arguing that each is a valid activity within its own context. ..."
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Cited by 3 (0 self)
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We approach the philosophy of mathematics via a discussion of the differences between classical mathematics and constructive mathematics, arguing that each is a valid activity within its own context.
A Formal Proof Of The Riesz Representation Theorem
"... This paper presents a formal proof of the Riesz representation theorem in the PVS theorem prover. The Riemann Stieltjes integral was defined in PVS, and the theorem relies on this integral. In order to prove the Riesz representation theorem, it was necessary to prove that continuous functions on a c ..."
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This paper presents a formal proof of the Riesz representation theorem in the PVS theorem prover. The Riemann Stieltjes integral was defined in PVS, and the theorem relies on this integral. In order to prove the Riesz representation theorem, it was necessary to prove that continuous functions on a closed interval are Riemann Stieltjes integrable with respect to any function of bounded variation. This result follows from the equivalence of the Riemann Stieltjes and Darboux Stieltjes integrals, which would have been a lengthy result to prove in PVS, so a simpler lemma was proved that captures the underlying concept of this integral equivalence. In order to prove the Riesz theorem, the Hahn Banach theorem was proved in the case where the normed linear spaces are the continuous and bounded functions on a closed interval. The proof of the Riesz theorem follows the proof in Haaser and Sullivan’s book Real Analysis. The formal proof of this result in PVS revealed an error in textbook’s proof. Indeed, the proof of the Riesz representation theorem is constructive, and the function constructed in the textbook does not satisfy a key property. This error illustrates the ability of formal verification to find logical errors. A specific counterexample is given to the proof in the textbook. Finally, a corrected proof of the Riesz representation theorem is presented.
Lattices and Orders in Isabelle/HOL
, 2008
"... We consider abstract structures of orders and lattices. Many fundamental concepts of lattice theory are developed, including dual structures, properties of bounds versus algebraic laws, lattice operations versus settheoretic ones etc. We also give example instantiations of lattices and orders, such ..."
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We consider abstract structures of orders and lattices. Many fundamental concepts of lattice theory are developed, including dual structures, properties of bounds versus algebraic laws, lattice operations versus settheoretic ones etc. We also give example instantiations of lattices and orders, such as direct products and function spaces. Wellknown properties are demonstrated, like the KnasterTarski Theorem for complete lattices. This formal theory development may serve as an example of applying Isabelle/HOL to the domain of mathematical reasoning about “axiomatic” structures. Apart from the simplytyped classical settheory of HOL, we employ Isabelle’s system of axiomatic type classes for expressing structures and functors in a lightweight manner. Proofs are expressed in the Isar language for readable formal proof, while aiming