ky/gen.lua

return function(ast, out)
    local function compile(chu)
        if chu.type == "chunk" then
            if chu.toplevel then
                for k, import in pairs(chu.imports) do
                    out("local %s = require(%q)\n", import[#import], table.concat(import, "."))
                end
                for k, var in pairs(chu.vars) do
                    out("local %s\n", k)
                end
                for k, expr in pairs(chu.vars) do
                    if expr then
                        out("%s=", k)
                        compile(expr)
                        out(";")
                    end
                end
                for k, t in pairs(chu.types) do
                    out("local %s={}%s.__index=%s;setmetatable(%s, %s)", k, k, k, k, k)
                    for _, m in pairs(t.members) do
                        if m.type == "field" then
                            -- Do nothing.
                        elseif m.type == "static" then
                            out("%s.%s=", k, m.name)
                            compile(m.value)
                            out(";")
                        else
                            error("Invalid AST")
                        end
                    end
                end
                out("return{")
                for k,v in pairs(chu.vars) do
                    out("%s=%s,", k, k)
                end
                for k,v in pairs(chu.types) do
                    out("%s=%s,", k, k)
                end
                out("}")
            else
                for k, stmt in ipairs(chu.stmts) do
                    compile(stmt)
                    
                    if stmt.type == 'call' then
                        out(";") --Safety delimiter.
                    end
                end
            end
        elseif chu.type == "function" then
            out("function(%s%s)", chu.is_constructor and "_," or "", table.concat(chu.args, ","))
            
            if SAFE_MODE then
                for k, argname in pairs(chu.args) do
                    local et = chu.et.args[k]
                    if et then
                        local checks = {}
                        if et.type == 'integer' or et.type == 'number' or et.type == 'string' or et.type == 'boolean' then
                            if et.type == 'integer' then
                                table.insert(checks, 'type(' .. argname .. ')=="number"')
                                table.insert(checks, argname .. '%1==0')
                            else
                                table.insert(checks, 'type(' .. argname .. ')=="'..et.type..'"')
                            end
                        elseif et.type == 'list' then
                            table.insert(checks, 'type(' .. argname .. ')=="table"')
                        end
                        if #checks > 0 then
                            out("assert(%s, %q);", table.concat(checks, " and "), string.format("Invalid argument %q", argname))
                        end
                    end
                end
            end
            
            if chu.is_constructor then
                out("local self=setmetatable({}, %s);", chu.et.ret.name)
            end
            
            compile(chu.chunk)
            
            if chu.is_constructor then
                out("return self;")
            end
            
            out("end")
        elseif chu.type == "let" then
            out("local %s", chu.var.name)
            
            if chu.expr then
                out("=")
                compile(chu.expr)
            end
            
            out(";")
        elseif chu.type == "num" then
            out("%g", chu.value)
        elseif chu.type == "var" then
            out("%s", chu.which.name)
        elseif chu.type == "binop" then
            local paren
            
            paren = chu.a.type == "binop" and chu.a.level > chu.level
            if paren then out("(") end
            compile(chu.a)
            if paren then out(")") end
            
            local op = chu.op
            
            if op == "**" then
                op = "^"
            elseif op == "/" and (not chu.a.et or chu.a.et.type == 'integer') and (not chu.b.et or chu.b.et.type == 'integer') then
                op = "//"
            end
            
            out("%s", op)
            
            paren = chu.b.type == "binop" and chu.b.level > chu.level
            if paren then out("(") end
            compile(chu.b)
            if paren then out(")") end
        elseif chu.type == "lengthof" then
            out("#(")
            compile(chu.sub)
            out(")")
        elseif chu.type == "dot" then
            compile(chu.a)
            out("%s%s", chu.colon and ":" or ".", chu.b)
        elseif chu.type == "index" then
            out("(")
            compile(chu.what)
            out(")[")
            compile(chu.idx)
            out("]")
        elseif chu.type == "call" then
            local guard = chu.type == 'binop'
            if guard then
                out("(")
            end
            compile(chu.what)
            if guard then
                out(")")
            end
            out("(")
            for k, v in pairs(chu.args) do
                compile(v)
                
                if k < #chu.args then
                    out(",")
                end
            end
            out(")")
        elseif chu.type == "dict" then
            out("{")
            for k, v in pairs(chu.mappings) do
                out("[")
                compile(k)
                out("]=")
                compile(v)
                out(",")
            end
            out("}")
        elseif chu.type == "list" then
            out("{")
            for k, v in pairs(chu.values) do
                out("[%i]=", k)
                compile(v)
                out(",")
            end
            out("}")
        elseif chu.type == "string" then
            out("%q", chu.value)
        elseif chu.type == "null" then
            out("nil")
        elseif chu.type == "return" then
            out("return ")
            compile(chu.expr)
            out(";")
        elseif chu.type == "if" then
            out("if ")
            compile(chu[1].pred)
            out(" then ")
            compile(chu[1].chu)
            
            for i = 2, #chu do
                out("elseif ")
                compile(chu[i].pred)
                out("then ")
                compile(chu[i].chu)
            end
            
            if chu.elsa then
                out("else ")
                compile(chu.elsa)
            end
            
            out("end;")
        elseif chu.type == "fori" then
            out("for " .. chu.varname .. "=")
            compile(chu.from)
            out(",")
            compile(chu.to)
            out("-1 do ")
            compile(chu.chu)
            out("end ")
        elseif chu.type == "loop" then
            out("while true do ")
            compile(chu.chu)
            out("end ")
        elseif chu.type == "break" then
            out("break ")
        elseif chu.type == "noop" then
        elseif chu.type == "exprstat" then
            compile(chu.expr)
            out(";")
        elseif chu.type == "assign" then
            compile(chu.dest)
            out("=")
            compile(chu.src)
            out(";")
        else
            error(string.format("Invalid AST node (type %q)", chu.type))
        end
    end
    return compile(ast)
end