mirror of
https://github.com/kanaka/mal.git
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125 lines
3.4 KiB
Plaintext
125 lines
3.4 KiB
Plaintext
readline = require './node_readline'
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{id, map, each} = require 'prelude-ls'
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{read_str} = require './reader'
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{pr_str} = require './printer'
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{Env} = require './env'
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repl_env = new Env null, do
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'+':
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type: \function
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value: (a, b) -> {type: \int, value: a.value + b.value}
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'-':
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type: \function
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value: (a, b) -> {type: \int, value: a.value - b.value}
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'*':
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type: \function
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value: (a, b) -> {type: \int, value: a.value * b.value}
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'/':
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type: \function
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value: (a, b) -> {type: \int, value: parseInt(a.value / b.value)}
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is-symbol = ({type, value}: ast, name) ->
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type == \symbol and value == name
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list-to-pairs = (list) ->
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[0 to (list.length - 2) by 2] \
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|> map (idx) -> [list[idx], list[idx+1]]
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eval_simple = (env, {type, value}: ast) ->
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switch type
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| \symbol => env.get value
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| \list, \vector => do
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type: type
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value: value |> map eval_ast env
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| otherwise => ast
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eval_ast = (env, {type, value}: ast) -->
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if type != \list then eval_simple env, ast
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else if value.length == 0 then ast
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else if value[0].type == \symbol
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params = value[1 to]
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switch value[0].value
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| 'def!' => eval_def env, params
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| 'let*' => eval_let env, params
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| otherwise => eval_apply env, value
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else
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eval_apply env, value
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check_params = (name, params, expected) ->
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if params.length != expected
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throw new Error "#{name} expected #{expected} parameters,
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got #{params.length}"
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eval_def = (env, params) ->
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check_params 'def!', params, 2
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# Name is in the first parameter, and is not evaluated.
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name = params[0]
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if name.type != \symbol
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throw new Error "expected a symbol for the first parameter
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of def!, got a #{name.type}"
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# Evaluate the second parameter and store
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# it under name in the env.
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env.set name.value, (eval_ast env, params[1])
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eval_let = (env, params) ->
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check_params 'let*', params, 2
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binding_list = params[0]
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if binding_list.type not in [\list \vector]
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throw new Error "expected 1st parameter of let* to
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be a binding list (or vector),
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got a #{binding_list.type}"
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else if binding_list.value.length % 2 != 0
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throw new Error "binding list of let* must have an even
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number of parameters"
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# Make a new environment with the
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# current environment as outer.
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let_env = new Env env
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# Evaluate all binding values in the
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# new environment.
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binding_list.value
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|> list-to-pairs
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|> each ([binding_name, binding_value]) ->
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if binding_name.type != \symbol
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throw new Error "expected a symbol as binding name,
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got a #{binding_name.type}"
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let_env.set binding_name.value, (eval_ast let_env, binding_value)
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# Evaluate the 'body' of let* with the new environment.
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eval_ast let_env, params[1]
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eval_apply = (env, list) ->
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[fn, ...args] = list |> map eval_ast env
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if fn.type != \function
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throw new Error fn.value, ' is not a function'
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fn.value.apply env, args
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rep = (line) ->
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line
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|> read_str
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|> eval_ast repl_env
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|> pr_str
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loop
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line = readline.readline 'user> '
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break if not line? or line == ''
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try
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console.log rep line
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catch {message}
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console.error message
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