Added debugging output to equivalence
Renamed a forgotten interface file for Debruijn.
Eliminate arrow_term from parser.
Merge branch 'brazil-standalone' of https://github.com/andrejbauer/tt into brazil-standalone
Added Syntax.occurs and Syntax.occurs_ty
Added Syntax.extract_pis
Added string_of_ty and string_of_term functions
Added more debugging (tracing) output
Deleted erroneous -> in the definition of plus
Improved type error formatting
Generalized the Syntax.transform helper function
Added a simple simplifier function to Syntax
Top-level simplifies types and definitions
Added occurrence counter; more aggressive simplify
Better indentation when printing contexts
Correctly shift the type in assume
Allow underscore in a product type
Fancy printing of products and lambdas
Occur checks
Have just one copy of occurs checks