Created
November 1, 2019 07:39
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| # !/usr/bin/env ruby | |
| def parse_let(tokens) | |
| let_token = ["keyword", tokens.slice!(0)] | |
| var_token = ["identifier", tokens.slice!(0)] | |
| eq_token = ["symbol", tokens.slice!(0)] | |
| exp = parse_expresssion(tokens) | |
| ["let_statement", let_token, var_token, eq_token, exp] | |
| end | |
| def parse_expresssion(tokens) | |
| parsed = parse_term(tokens) | |
| ["expression", parsed] | |
| end | |
| def parse_term(tokens) | |
| parsed = ["term"] | |
| if tokens[0] == "+" | |
| parsed << ["symbol", tokens.slice!(0)] | |
| end | |
| parsed << ["integer_constant", tokens.slice!(0)] | |
| if tokens[0] == "+" | |
| parsed << parse_term(tokens) | |
| end | |
| parsed | |
| end | |
| tokens = %w[let var = 1 + 1] | |
| tree = parse_let(tokens) | |
| pp tree | |
| @ind = 0 | |
| def parse!(t) | |
| case t[0] | |
| when "keyword", "symbol", "identifier", "integer_constant" | |
| print ' ' * (@ind * 2) | |
| pp "<#{t[0]}> #{t[1]} </#{t[0]}>" | |
| else | |
| print ' ' * (@ind * 2) | |
| pp "<#{t[0]}>" | |
| @ind += 1 | |
| case t[0] | |
| when "let_statement" | |
| parse!(t[1]) | |
| parse!(t[2]) | |
| parse!(t[3]) | |
| parse!(t[4]) | |
| when "expression" | |
| parse!(t[1]) | |
| when "term" | |
| parse!(t[1]) | |
| parse!(t[2]) unless t[2].nil? | |
| end | |
| @ind -= 1 | |
| print ' ' * (@ind * 2) | |
| pp "</#{t[0]}>" | |
| end | |
| end | |
| parse!(tree) |
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