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| author | Case Duckworth | 2024-03-31 22:14:22 -0500 |
|---|---|---|
| committer | Case Duckworth | 2024-03-31 22:14:22 -0500 |
| commit | fc8989a2019922208c1e054a7a08a44ed7db1a35 (patch) | |
| tree | 062517c2b0d4e746c2b2bf7be36c9b741a07d62e | |
| parent | Expose `specials' (diff) | |
| download | lam-fc8989a2019922208c1e054a7a08a44ed7db1a35.tar.gz lam-fc8989a2019922208c1e054a7a08a44ed7db1a35.zip | |
Add quasiquote
| -rw-r--r-- | eval.lua | 44 |
1 files changed, 35 insertions, 9 deletions
| diff --git a/eval.lua b/eval.lua index e13fb97..714c67e 100644 --- a/eval.lua +++ b/eval.lua | |||
| @@ -48,17 +48,43 @@ function m.procedure (params, body, env) | |||
| 48 | return setmetatable(t, mt) | 48 | return setmetatable(t, mt) |
| 49 | end | 49 | end |
| 50 | 50 | ||
| 51 | local specials = { | ||
| 52 | m.specials = { | 51 | m.specials = { |
| 53 | -- each of these takes R (a list of args) and E (an environment) | 52 | -- each of these takes R (a list of args) and E (an environment) |
| 54 | quote = | 53 | quote = function (r, e) return r[1] end, |
| 55 | function (r, e) return r[1] end, | 54 | quasiquote = |
| 56 | define = | 55 | function (r, e) |
| 57 | function (r, e) rawset(e, r[1], m.eval(r[2][1], e)) end, | 56 | local x = r[1] |
| 58 | lambda = | 57 | if not type.islist(x) or x == type.null then |
| 59 | function (r, e) return m.procedure(r[1], r[2], e) end, | 58 | return x |
| 60 | ["set!"] = | 59 | end |
| 61 | function (r, e) e[r[1]] = m.eval(r[2][1], e) end, | 60 | local QQ, fin = {}, nil |
| 61 | local car, cdr = x[1], x[2] | ||
| 62 | while cdr do | ||
| 63 | if type.islist(car) then | ||
| 64 | if car[1] == "unquote" then | ||
| 65 | table.insert(QQ, | ||
| 66 | m.eval(car[2][1], e)) | ||
| 67 | elseif car[1] == "unquote-splicing" then | ||
| 68 | local usl = m.eval(car[2][1], e) | ||
| 69 | if not type.islist(usl) then | ||
| 70 | fin = usl | ||
| 71 | break | ||
| 72 | end | ||
| 73 | while usl[2] do | ||
| 74 | table.insert(QQ, usl[1]) | ||
| 75 | usl = usl[2] | ||
| 76 | end | ||
| 77 | end | ||
| 78 | else | ||
| 79 | table.insert(QQ, car) | ||
| 80 | end | ||
| 81 | car, cdr = cdr[1], cdr[2] | ||
| 82 | end | ||
| 83 | return type.list(QQ, fin) | ||
| 84 | end, | ||
| 85 | define = function (r, e) rawset(e, r[1], m.eval(r[2][1], e)) end, | ||
| 86 | lambda = function (r, e) return m.procedure(r[1], r[2], e) end, | ||
| 87 | ["set!"] = function (r, e) e[r[1]] = m.eval(r[2][1], e) end, | ||
| 62 | ["if"] = | 88 | ["if"] = |
| 63 | function (r, e) | 89 | function (r, e) |
| 64 | local test, conseq, alt = | 90 | local test, conseq, alt = |