Sure; a simple definition is at https://tromp.github.io/cl/Binary_lambda_calculus.html#Halting_probability https://tromp.github.io/cl/Binary_lambda_calculus.htm

Sure; a simple definition is at https://tromp.github.io/cl/Binary_lambda_calculus.html#Halting_probability https://tromp.github.io/cl/Binary_lambda_calculus.html#Halti...