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Print graphical lambda calculus
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| from arpeggio.cleanpeg import ParserPEG | |
| from arpeggio import PTNodeVisitor, visit_parse_tree | |
| GRAMMAR=r""" | |
| full = expr EOF | |
| expr = var / function / application | |
| function = "/" var "." expr | |
| application = "(" expr expr ")" | |
| var = r"\w+" | |
| """ | |
| parser = ParserPEG(GRAMMAR, root_rule_name="full") | |
| def _make_top_pipe(cols): | |
| last_non_pipe=max(i for i, col in enumerate(cols) if col[0]!=" ") | |
| for i in range(last_non_pipe+1, len(cols)): | |
| cols[i]="─"+cols[i][1:] | |
| if cols[last_non_pipe][0]=="┐": | |
| cols[last_non_pipe]="┬"+cols[last_non_pipe][1:] | |
| return cols | |
| class MyVisitor(PTNodeVisitor): | |
| def visit_full(self, node, children): | |
| return children[0] | |
| def visit_expr(self, node, children): | |
| return children[0] | |
| def visit_function(self, node, children): | |
| var, expr = children | |
| return _make_top_pipe(expr) + ["─"] + var | |
| def visit_application(self, node, children): | |
| func, arg = children | |
| return _make_top_pipe(func) + ["─"] + [("┐" if i==0 else " ") + col for i, col in enumerate(arg)] | |
| def visit_var(self, node, children): | |
| return list(str(node)) | |
| def p(text): | |
| tree = parser.parse(text) | |
| tree2 = visit_parse_tree(tree, MyVisitor()) | |
| print("\n".join("".join(row) for row in zip_longest(*tree2, fillvalue=" "))) | |
| for name, lam in [ | |
| ("Abstraction", "/x.M"), | |
| ("Application", "(f x)"), | |
| ("true", "/x./y.x"), | |
| ("false", "/x./y.y"), | |
| ("and", "/a./b.((a b) a)"), | |
| ("0", "/f./x.x"), | |
| ("1", "/f./x.(f x)"), | |
| ("2", "/f./x.(f (f x))"), | |
| ("succ", "/n./f./x.(f ((n f) x))"), | |
| ("Y", "/g.(/x.(g (x x)) /x.(g (x x)))"), | |
| ("Omega", "(/x.(x x) /x.(x x))"), | |
| ]: | |
| print(f"{name}: {lam}") | |
| p(lam) | |
| print() |
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