# .tlv file generated by https://github.com/akkartik/teliva
# You may edit it if you are careful; however, you may see cryptic errors if you
# violate Teliva's assumptions.
#
# .tlv files are representations of Teliva programs. Teliva programs consist of
# sequences of definitions. Each definition is a table of key/value pairs. Keys
# and values are both strings.
#
# Lines in .tlv files always follow exactly one of the following forms:
# - comment lines at the top of the file starting with '#' at column 0
# - beginnings of definitions starting with '- ' at column 0, followed by a
# key/value pair
# - key/value pairs consisting of ' ' at column 0, containing either a
# spaceless value on the same line, or a multi-line value
# - multiline values indented by more than 2 spaces, starting with a '>'
#
# If these constraints are violated, Teliva may unceremoniously crash. Please
# report bugs at http://akkartik.name/contact
- __teliva_timestamp: original
str_helpers:
>-- some string helpers from http://lua-users.org/wiki/StringIndexing
>
>-- index characters using []
>getmetatable('').__index = function(str,i)
> if type(i) == 'number' then
> return str:sub(i,i)
> else
> return string[i]
> end
>end
>
>-- ranges using (), selected bytes using {}
>getmetatable('').__call = function(str,i,j)
> if type(i)~='table' then
> return str:sub(i,j)
> else
> local t={}
> for k,v in ipairs(i) do
> t[k]=str:sub(v,v)
> end
> return table.concat(t)
> end
>end
>
>-- iterate over an ordered sequence
>function q(x)
> if type(x) == 'string' then
> return x:gmatch('.')
> else
> return ipairs(x)
> end
>end
>
>-- insert within string
>function string.insert(str1, str2, pos)
> return str1:sub(1,pos)..str2..str1:sub(pos+1)
>end
>
>function string.remove(s, pos)
> return s:sub(1,pos-1)..s:sub(pos+1)
>end
>
>function string.pos(s, sub)
> return string.find(s, sub, 1, true) -- plain=true to disable regular expressions
>end
>
>-- TODO: backport utf-8 support from Lua 5.3
- __teliva_timestamp: original
check:
>function check(x, msg)
> if x then
> Window:addch('.')
> else
> print('F - '..msg)
> print(' '..str(x)..' is false/nil')
> teliva_num_test_failures = teliva_num_test_failures + 1
> -- overlay first test failure on editors
> if teliva_first_failure == nil then
> teliva_first_failure = msg
> end
> end
>end
- __teliva_timestamp: original
check_eq:
>function check_eq(x, expected, msg)
> if eq(x, expected) then
> Window:addch('.')
> else
> print('F - '..msg)
> print(' expected '..str(expected)..' but got '..str(x))
> teliva_num_test_failures = teliva_num_test_failures + 1
> -- overlay first test failure on editors
> if teliva_first_failure == nil then
> teliva_first_failure = msg
> end
> end
>end
- __teliva_timestamp: original
eq:
>function eq(a, b)
> if type(a) ~= type(b) then return false end
> if type(a) == 'table' then
> if #a ~= #b then return false end
> for k, v in pairs(a) do
> if b[k] ~= v then
> return false
> end
> end
> for k, v in pairs(b) do
> if a[k] ~= v then
> return false
> end
> end
> return true
> end
> return a == b
>end
- __teliva_timestamp: original
str:
>-- smarter tostring
>-- slow; used only for debugging
>function str(x)
> if type(x) == 'table' then
> local result = ''
> result = result..#x..'{'
> for k, v in pairs(x) do
> result = result..str(k)..'='..str(v)..', '
> end
> result = result..'}'
> return result
> elseif type(x) == 'string' then
> return '"'..x..'"'
> end
> return tostring(x)
>end
- __teliva_timestamp: original
menu:
>-- To show app-specific hotkeys in the menu bar, add hotkey/command
>-- arrays of strings to the menu array.
>menu = {}
- __teliva_timestamp: original
Window:
>Window = curses.stdscr()
- __teliva_timestamp: original
render:
>function render(window)
> window:clear()
> -- draw stuff to screen here
> window:attron(curses.A_BOLD)
> window:mvaddstr(1, 5, "example app")
> window:attrset(curses.A_NORMAL)
> for i=0,15 do
> window:attrset(curses.color_pair(i))
> window:mvaddstr(3+i, 5, "========================")
> end
> window:refresh()
>end
- __teliva_timestamp: original
menu:
>-- To show app-specific hotkeys in the menu bar, add hotkey/command
>-- arrays of strings to the menu array.
>menu = {}
- __teliva_timestamp: original
update:
>function update(window)
> local key = window:getch()
> -- process key here
>end
- __teliva_timestamp: original
init_colors:
>function init_colors()
> for i=0,7 do
> curses.init_pair(i, i, -1)
> end
> curses.init_pair(8, 7, 0)
> curses.init_pair(9, 7, 1)
> curses.init_pair(10, 7, 2)
> curses.init_pair(11, 7, 3)
> curses.init_pair(12, 7, 4)
> curses.init_pair(13, 7, 5)
> curses.init_pair(14, 7, 6)
> curses.init_pair(15, -1, 15)
>end
- __teliva_timestamp: original
main:
>function main()
> init_colors()
>
> while true do
> render(Window)
> update(Window)
> end
>end
- __teliva_timestamp: original
eval:
>function eval(x, env)
> function symeq(x, s)
> return x and x.sym == s
> end
> if x.sym then
> return lookup(env, x.sym)
> elseif atom(x) then
> return x
> -- otherwise x is a pair
> elseif symeq(x.car, 'quote') then
> return x.cdr
> elseif unary_functions[x.car.sym] then
> return eval_unary(x, env)
> elseif binary_functions[x.car.sym] then
> return eval_binary(x, env)
> -- special forms that don't always eval all their args
> elseif symeq(x.car, 'if') then
> return eval_if(x, env)
> elseif symeq(x.car.car, 'fn') then
> return eval_fn(x, env)
> elseif symeq(x.car.car, 'label') then
> return eval_label(x, env)
> end
>end
- __teliva_timestamp: original
eval_unary:
>function eval_unary(x, env)
> return unary_functions[x.car.sym](eval(x.cdr.car, env))
>end
- __teliva_timestamp: original
eval_binary:
>function eval_binary(x, env)
> return binary_functions[x.car.sym](eval(x.cdr.car, env))
>end
- __teliva_timestamp: original
unary_functions:
>-- format: lisp name = lua function that implements it
>unary_functions = {
> atom=atom,
> car=car,
> cdr=cdr,
>}
- __teliva_timestamp: original
binary_functions:
>-- format: lisp name = lua function that implements it
>binary_functions = {
> cons=cons,
> iso=iso,
>}
- __teliva_timestamp: original
lookup:
>function lookup(env, s)
> if env[s] then return env[s] end
> if env.next then return lookup(env.next, s) end
>end
- __teliva_timestamp: original
eval_if:
>function eval_if(x, env)
> -- syntax: (if check b1 b2)
> local check = x.cdr.car
> local b1 = x.cdr.cdr.car
> local b2 = x.cdr.cdr.cdr.car
> if eval(check, env) then
> return eval(b1, env)
> else
> return eval(b2, env)
> end
>end
- __teliva_timestamp: original
eval_fn:
>function eval_fn(x, env)
> -- syntax: ((fn params body*) args*)
> local callee = x.car
> local args = x.cdr
> local params = callee.cdr.car
> local body = callee.cdr.cdr
> return eval_exprs(body,
> bind_env(params, args, env))
>end
- __teliva_timestamp: original
bind_env:
>function bind_env(params, args, env)
> if params == nil then return env end
> local result = {next=env}
> while true do
> result[params.car.sym] = eval(args.car, env)
> params = params.cdr
> args = args.cdr
> if params == nil then break end
> end
> return result
>end
- __teliva_timestamp: original
eval_exprs:
>function eval_exprs(xs, env)
> local result = nil
> while xs do
> result = eval(xs.car, env)
> xs = xs.cdr
> end
> return result
>end
- __teliva_timestamp: original
eval_label:
>function eval_label(x, env)
> -- syntax: ((label f (fn params body*)) args*)
> local callee = x.car
> local args = x.cdr
> local f = callee.cdr.car
> local fn = callee.cdr.cdr.car
> return eval({car=fn, cdr=args},
> bind_env({f}, {callee}, env))
>end
- __teliva_timestamp: original
atom:
>function atom(x)
> return x == nil or x.num or x.char or x.str or x.sym
>end
- __teliva_timestamp: original
car:
>function car(x) return x.car end
- __teliva_timestamp: original
cdr:
>function cdr(x) return x.cdr end
- __teliva_timestamp: original
cons:
>function cons(x, y) return {car=x, cdr=y} end
- __teliva_timestamp: original
doc:main:
>John McCarthy's Lisp -- without the metacircularity
>If you know Lua, this version might be easier to understand.
>
>Words highlighted like [[this]] are suggestions for places to jump to using ctrl-g (see the menu below).
>You can always jump back here using ctrl-b (for 'big picture').
>
>Lisp is a programming language that manipulates objects of a few different types.
>There are a few _atomic_ types, and one type that can combine them.
>The atomic types are what you would expect: numbers, characters, strings, symbols (variables). You can add others.
>
>The way to combine them is the [[cons]] table which has just two keys: a [[car]] and a [[cdr]]. Both can hold objects, either atoms or other cons tables.
>
>We'll now build an interpreter that can run programs constructed out of cons tables.
>
>One thing we'll need for an interpreter is a symbol table (env) that maps symbols to values (objects).
>We'll just use a Lua table for this purpose, but with one tweak: a _next_ pointer that allows us to combine tables together.
>See [[lookup]] now to get a sense for how we'll use envs.
>
>Lisp programs are just cons tables and atoms nested to arbitrary depths, constructing trees. A Lisp interpreter walks the tree of code,
>performing computations. Since cons tables can point to other cons tables, the tree-walker interpreter [[eval]] is recursive.
>As the interpreter gets complex, we'll extract parts of it into their own helper functions: [[eval_unary]], [[eval_binary]], [[eval_if]], and so on.
>The helper functions contain recursive calls to [[eval]], so that [[eval]] becomes indirectly recursive, and [[eval]] together with its helpers
>is mutually recursive. I sometimes find it helpful to think of them all as just one big function.
>
>All these mutually recursive functions take the same arguments: a current expression 'x' and the symbol table 'env'.
>But really, most of the interpreter is just walking the tree of expressions. Only two functions care about the internals of 'env':
> - [[lookup]] which reads within env as we saw before
> - [[bind_env]] which creates a new _scope_ of symbols for each new function call.
>More complex Lisps add even more arguments to every. single. helper. Each arg will still only really matter to a couple of functions.
>But we still have to pass them around all over the place.
>
>Hopefully this quick overview will help you get a sense for this codebase.
>
>Here's a reference list of eval helpers: [[eval_unary]], [[eval_binary]], [[eval_if]], [[eval_fn]], [[eval_exprs]], [[eval_label]]
>More complex Lisps with more features will likely add helpers for lumpy bits of the language.
>Here's a list of primitives implemented in Lua: [[atom]], [[car]], [[cdr]], [[cons]], [[iso]] (for 'isomorphic'; comparing trees all the way down to the leaves)
>Here's a list of _constructors_ for creating objects of different types: [[num]], [[char]], [[str]], [[sym]] (and of course [[cons]])
>I should probably add more primitives for operating on numbers, characters and strings..
- __teliva_timestamp: original
iso:
>function iso(x, y)
> if x == nil then return y == nil end
> local done={}
> -- watch out for the rare cyclical expression
> if done[x] then return done[x] == y end
> done[x] = y
> if atom(x) then
> if not atom(y) then return nil end
> for k, v in pairs(x) do
> if y[k] ~= v then return nil end
> end
> return true
> end
> for k, v in pairs(x) do
> if not iso(y[k], v) then return nil end
> end
> for k, v in pairs(y) do
> if not iso(x[k], v) then return nil end
> end
> return true
>end