GitLab

	Abstractions are required to have at least one parameter now
	Add tests for evaluation
	Small fix in compilation of let expression (still not work though)

	branches in a match now, only variables, pairs and constants

	compile externals now, remains to make the link between parser and
	lambda.

	local and external lambda files

	GRAMMAR updated

	GRAMMAR file added; some fixes.

of polymorphism. Lexer complete. Parser to do.

- fix one more problem with internalize
- fix variance/contravariance problem in substituterec
- cleanup