diff options
| author | Case Duckworth | 2024-03-23 15:51:07 -0500 |
|---|---|---|
| committer | Case Duckworth | 2024-03-23 15:51:27 -0500 |
| commit | 4fb6e90474c8e9292df1a6210b8de260dd253ccb (patch) | |
| tree | ae56acdb2d090ed36184b36635f41b692a652188 /eval.lua | |
| parent | Add a bunch of base functions (diff) | |
| download | lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.tar.gz lam-4fb6e90474c8e9292df1a6210b8de260dd253ccb.zip | |
Break special forms out into their own table
Diffstat (limited to 'eval.lua')
| -rw-r--r-- | eval.lua | 53 |
1 files changed, 36 insertions, 17 deletions
| diff --git a/eval.lua b/eval.lua index 9b1c315..610b902 100644 --- a/eval.lua +++ b/eval.lua | |||
| @@ -53,6 +53,40 @@ function eval.Proc (params, body, env) | |||
| 53 | return setmetatable(v, mt) | 53 | return setmetatable(v, mt) |
| 54 | end | 54 | end |
| 55 | 55 | ||
| 56 | local specials = { | ||
| 57 | quote = | ||
| 58 | function (args, env) | ||
| 59 | return args.car | ||
| 60 | end, | ||
| 61 | define = | ||
| 62 | function (args, env) | ||
| 63 | rawset(env, args.car, eval(args.cdr.car, env)) | ||
| 64 | return nil | ||
| 65 | end, | ||
| 66 | lambda = | ||
| 67 | function (args, env) | ||
| 68 | return Proc(args.car, args.cdr, env) | ||
| 69 | end, | ||
| 70 | ["set!"] = | ||
| 71 | function (args, env) | ||
| 72 | env[args.car] = eval(args.cdr.car, env) | ||
| 73 | return nil | ||
| 74 | end, | ||
| 75 | ["if"] = | ||
| 76 | function (args, env) | ||
| 77 | local test, conseq, alt = | ||
| 78 | args.car, args.cdr.car, args.cdr.cdr.car | ||
| 79 | if eval(test) | ||
| 80 | then return eval(conseq) | ||
| 81 | else return eval(alt) | ||
| 82 | end | ||
| 83 | end, | ||
| 84 | -- TODO: include, import, define-syntax, define-values(?) ... | ||
| 85 | } | ||
| 86 | -- Aliases | ||
| 87 | specials.lam = specials.lambda | ||
| 88 | specials.def = specials.define | ||
| 89 | |||
| 56 | function eval.eval (x, env) | 90 | function eval.eval (x, env) |
| 57 | env = env or base.env | 91 | env = env or base.env |
| 58 | if isa(x, "Symbol") then | 92 | if isa(x, "Symbol") then |
| @@ -61,23 +95,8 @@ function eval.eval (x, env) | |||
| 61 | return x | 95 | return x |
| 62 | else | 96 | else |
| 63 | local op, args = x.car, x.cdr | 97 | local op, args = x.car, x.cdr |
| 64 | if op == "quote" then | 98 | if specials[op] then |
| 65 | return args.car | 99 | return specials[op](args, env) |
| 66 | elseif op == "define" or op == "def" then | ||
| 67 | rawset(env, args.car, eval.eval(args.cdr.car, env)) | ||
| 68 | return nil | ||
| 69 | elseif op == "set!" then | ||
| 70 | env[args.car] = eval.eval(args.cdr.car, env) | ||
| 71 | elseif op == "lambda" or op == "lam" then | ||
| 72 | return eval.Proc(args.car, args.cdr, env) | ||
| 73 | elseif op == "if" then | ||
| 74 | assert(not isNull(args.cdr), "Malformed 'if'") | ||
| 75 | local test, conseq, alt = | ||
| 76 | args.car, args.cdr.car, args.cdr.cdr.car | ||
| 77 | if eval.eval(test) | ||
| 78 | then return eval.eval(conseq) | ||
| 79 | else return eval.eval(alt) | ||
| 80 | end | ||
| 81 | else -- procedure | 100 | else -- procedure |
| 82 | local proc = eval.eval(op, env) | 101 | local proc = eval.eval(op, env) |
| 83 | local params = {} | 102 | local params = {} |