# Questions tagged [combinatory-algebra]

The combinatory-algebra tag has no usage guidance.

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### Semi universal proper combinator

It is known that the two combinators S and K defined by Sxyz=xz(yz), Kxy=x, generate all other possible combinators. It is also known that no single proper combinator (combinator that can be defined ...

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### Proper full submodels of full models of type theory

Let $N$ be the standard full model of the simply typed lambda calculus with infinite base type $o$ and let $X$ be an infinite and coinfinite subset of $N(o)$. I want to know if there's a full ...

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### combinator SSS(SS)SS is not strongly normalizing. Why?

I highly speculate that combinator SSS(SS)SS is not strongly normalizing. What is the argument for the non strong normalization?

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### Difference between a 'calculus' and an 'algebra'

What is really the conceptual difference between a calculus and an algebra.
Eg. Is SKI combinator calculus really a calculus?
A friend claims that free variables are fundamental for a calculus, and ...