Introduce is_a() and stop checking `class` field explicitly.
Chris Pressey
1 year, 8 months ago
| 132 | 132 | |
| 133 | 133 | * Interned strings and modules? Hash-consing, even? |
| 134 | 134 | * Tracebacks, or at least line/column, or at least "in function..." |
| 135 | * isa instead of .class == | |
| 136 | 135 | |
| 137 | 136 | ### Compiler |
| 138 | 137 | |
| 152 | 151 | an "implementation module" written in language X will be used when |
| 153 | 152 | the code is compiled to X. But the module defines the semantics. |
| 154 | 153 | |
| 154 | ### Desugar | |
| 155 | ||
| 156 | * cond -> nested if's | |
| 157 | * let* -> nested let1's | |
| 158 | ||
| 155 | 159 | ### Forms |
| 156 | 160 | |
| 157 | 161 | * `if` |
| 30 | 30 | |
| 31 | 31 | local emit_symbols = function(sexp) |
| 32 | 32 | while sexp ~= Nil do |
| 33 | if sexp.class == Cons then | |
| 33 | if is_a(sexp, Cons) then | |
| 34 | 34 | emit_symbol(sexp.head()) |
| 35 | 35 | if sexp.tail() ~= Nil then |
| 36 | 36 | emit(",") |
| 43 | 43 | end |
| 44 | 44 | |
| 45 | 45 | fields.compile_expr = function(ast) |
| 46 | if ast.class == Cons then | |
| 46 | if is_a(ast, Cons) then | |
| 47 | 47 | local head = ast.head() |
| 48 | if head.class == Symbol then | |
| 48 | if is_a(head, Symbol) then | |
| 49 | 49 | if head.text() == "quote" then |
| 50 | 50 | fields.compile_quote(ast.tail()) |
| 51 | 51 | elseif head.text() == "let*" then |
| 64 | 64 | else |
| 65 | 65 | error("Can't compile application not in A-normal form: " .. depict(ast)) |
| 66 | 66 | end |
| 67 | elseif ast.class == Symbol then | |
| 67 | elseif is_a(ast, Symbol) then | |
| 68 | 68 | fields.compile_lookup(ast) |
| 69 | elseif ast.class == String or ast.class == Number or ast.class == Boolean then | |
| 69 | elseif is_a(ast, String) or is_a(ast, Number) or is_a(ast, Boolean) then | |
| 70 | 70 | fields.compile_literal(ast) |
| 71 | 71 | else |
| 72 | 72 | error("Unsupported form for compilation: " .. depict(ast)) |
| 75 | 75 | |
| 76 | 76 | fields.compile_exprs = function(sexp, inter) |
| 77 | 77 | while sexp ~= Nil do |
| 78 | if sexp.class == Cons then | |
| 78 | if is_a(sexp, Cons) then | |
| 79 | 79 | fields.compile_expr(sexp.head()) |
| 80 | 80 | if sexp.tail() ~= Nil then |
| 81 | 81 | inter() |
| 115 | 115 | |
| 116 | 116 | fields.compile_bindings = function(sexp) |
| 117 | 117 | while sexp ~= Nil do |
| 118 | if sexp.class == Cons then | |
| 118 | if is_a(sexp, Cons) then | |
| 119 | 119 | local pair = sexp.head() |
| 120 | 120 | debug("compiler", depict(pair)) |
| 121 | 121 | fields.compile_binding(pair.head(), pair.tail().head()) |
| 36 | 36 | |
| 37 | 37 | bind_all = function(bindings, env) |
| 38 | 38 | local binding, value |
| 39 | while bindings.class ~= Nil do | |
| 39 | while bindings ~= Nil do | |
| 40 | 40 | binding = bindings.head() |
| 41 | 41 | value = eval_expr(binding.tail().head(), env) |
| 42 | 42 | env = bind(binding.head(), value, env) |
| 47 | 47 | |
| 48 | 48 | eval_exprs = function(sexp, env) |
| 49 | 49 | local exprs = {} |
| 50 | while sexp.class ~= Nil do | |
| 51 | if sexp.class == Cons then | |
| 50 | while sexp ~= Nil do | |
| 51 | if is_a(sexp, Cons) then | |
| 52 | 52 | table.insert(exprs, eval_expr(sexp.head(), env)) |
| 53 | 53 | else |
| 54 | 54 | error("assertion failed: not a Cons") |
| 59 | 59 | end |
| 60 | 60 | |
| 61 | 61 | eval_expr = function(ast, env) |
| 62 | if ast.class == Cons then | |
| 62 | if is_a(ast, Cons) then | |
| 63 | 63 | local head = ast.head() |
| 64 | if head.class == Symbol then | |
| 64 | if is_a(head, Symbol) then | |
| 65 | 65 | if head.text() == "quote" then |
| 66 | 66 | return ast.tail().head() |
| 67 | 67 | elseif head.text() == "let*" then |
| 79 | 79 | while branch.class ~= Nil do |
| 80 | 80 | local b = branch.head() |
| 81 | 81 | local test = b.head() |
| 82 | if test.class == Symbol and test.text() == "else" then | |
| 82 | if is_a(test, Symbol) and test.text() == "else" then | |
| 83 | 83 | return eval_expr(b.tail().head(), env) |
| 84 | 84 | else |
| 85 | 85 | local result = eval_expr(test, env) |
| 86 | if result.class == Boolean and result.value() then | |
| 86 | if is_a(result, Boolean) and result.value() then | |
| 87 | 87 | return eval_expr(b.tail().head(), env) |
| 88 | 88 | end |
| 89 | 89 | end |
| 116 | 116 | fn = eval_expr(ast.head(), env) |
| 117 | 117 | return fn(eval_exprs(ast.tail(), env)) |
| 118 | 118 | end |
| 119 | elseif ast.class == Symbol then | |
| 119 | elseif is_a(ast, Symbol) then | |
| 120 | 120 | local value = env[ast.text()] |
| 121 | 121 | if value == nil then |
| 122 | 122 | error("Unbound symbol: " .. ast.text()) |
| 123 | 123 | end |
| 124 | 124 | return value |
| 125 | elseif ast.class == String or ast.class == Number or ast.class == Boolean then | |
| 125 | elseif is_a(ast, String) or is_a(ast, Number) or is_a(ast, Boolean) then | |
| 126 | 126 | return ast |
| 127 | 127 | else |
| 128 | 128 | error("Unsupported form for evaluation: " .. depict(ast)) |
| 80 | 80 | local s = "" |
| 81 | 81 | if type(sexp) == "function" then |
| 82 | 82 | return "<<" .. tostring(sexp) .. ">>" |
| 83 | elseif sexp.class == Nil then | |
| 83 | elseif sexp == Nil then | |
| 84 | 84 | return "()" |
| 85 | elseif sexp.class == Cons then | |
| 85 | elseif is_a(sexp, Cons) then | |
| 86 | 86 | s = s .. "(" |
| 87 | 87 | s = s .. depict(sexp.head()) |
| 88 | 88 | sexp = sexp.tail() |
| 89 | 89 | local done = false |
| 90 | 90 | while not done do |
| 91 | if sexp.class == Cons then | |
| 91 | if is_a(sexp, Cons) then | |
| 92 | 92 | s = s .. " " |
| 93 | 93 | s = s .. depict(sexp.head()) |
| 94 | 94 | sexp = sexp.tail() |
| 101 | 101 | end |
| 102 | 102 | s = s .. ")" |
| 103 | 103 | return s |
| 104 | elseif sexp.class == Symbol then | |
| 104 | elseif is_a(sexp, Symbol) then | |
| 105 | 105 | return sexp.text() |
| 106 | elseif sexp.class == String then | |
| 106 | elseif is_a(sexp, String) then | |
| 107 | 107 | return "\"" .. sexp.text() .. "\"" |
| 108 | elseif sexp.class == Number then | |
| 108 | elseif is_a(sexp, Number) then | |
| 109 | 109 | return tostring(sexp.value()) |
| 110 | elseif sexp.class == Boolean then | |
| 110 | elseif is_a(sexp, Boolean) then | |
| 111 | 111 | if sexp.value() then return "#t" else return "#f" end |
| 112 | 112 | else |
| 113 | 113 | error("Invalid lua representation of s-expression: " .. render(sexp) .. ": " .. type(sexp)) |
| 30 | 30 | list_p = function(value) |
| 31 | 31 | if type(value) == "function" then |
| 32 | 32 | return False |
| 33 | elseif value.class == Nil then | |
| 33 | elseif value == Nil then | |
| 34 | 34 | return True |
| 35 | elseif value.class == Cons then | |
| 35 | elseif is_a(value, Cons) then | |
| 36 | 36 | return list_p(value.tail()) |
| 37 | 37 | else |
| 38 | 38 | return False |
| 48 | 48 | return False |
| 49 | 49 | elseif a.class ~= b.class then |
| 50 | 50 | return False |
| 51 | elseif a.class == Nil then | |
| 51 | elseif a == Nil then | |
| 52 | 52 | return True |
| 53 | elseif a.class == String or a.class == Symbol then | |
| 53 | elseif is_a(a, String) or is_a(a, Symbol) then | |
| 54 | 54 | return Boolean.value(a.text() == b.text()) |
| 55 | elseif a.class == Number or a.class == Boolean then | |
| 55 | elseif is_a(a, Number) or is_a(a, Boolean) then | |
| 56 | 56 | return Boolean.value(a.value() == b.value()) |
| 57 | elseif a.class == Cons then | |
| 57 | elseif is_a(a, Cons) then | |
| 58 | 58 | return equal_p(a.head(), b.head()) and equal_p(a.tail(), b.tail()) |
| 59 | 59 | else |
| 60 | 60 | return False |
| 183 | 183 | end |
| 184 | 184 | |
| 185 | 185 | fields.eval_toplevel = function(expr, env, module) |
| 186 | if expr.class == Cons then | |
| 187 | if expr.head().class == Symbol then | |
| 186 | if is_a(expr, Cons) then | |
| 187 | if is_a(expr.head(), Symbol) then | |
| 188 | 188 | if expr.head().text() == "define" then |
| 189 | 189 | local name = expr.tail().head() |
| 190 | 190 | local dexpr = expr.tail().tail().head() |