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https://github.com/kanaka/mal.git
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54 lines
1.4 KiB
Nim
54 lines
1.4 KiB
Nim
import rdstdin, tables, sequtils, types, reader, printer
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proc read(str: string): MalType = str.read_str
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proc eval(ast: MalType, env: Table[string, MalType]): MalType
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proc eval_ast(ast: MalType, env: Table[string, MalType]): MalType =
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case ast.kind
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of Symbol:
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if not env.hasKey(ast.str):
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raise newException(ValueError, "'" & ast.str & "' not found")
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result = env[ast.str]
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of List:
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result = list ast.list.mapIt(MalType, it.eval(env))
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of Vector:
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result = vector ast.list.mapIt(MalType, it.eval(env))
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of HashMap:
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result = hash_map()
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for k, v in ast.hash_map.pairs:
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result.hash_map[k] = v.eval(env)
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else:
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result = ast
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proc eval(ast: MalType, env: Table[string, MalType]): MalType =
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case ast.kind
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of List:
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if ast.list.len == 0: return ast
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let el = ast.eval_ast(env)
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el.list[0].fun(el.list[1 .. ^1])
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else:
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ast.eval_ast(env)
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proc print(exp: MalType): string = exp.pr_str
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template wrapNumberFun(op): untyped =
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fun proc(xs: varargs[MalType]): MalType = number op(xs[0].number, xs[1].number)
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let repl_env = toTable({
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"+": wrapNumberFun `+`,
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"-": wrapNumberFun `-`,
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"*": wrapNumberFun `*`,
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"/": wrapNumberFun `div`,
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})
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proc rep(str: string): string =
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str.read.eval(repl_env).print
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while true:
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try:
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let line = readLineFromStdin("user> ")
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echo line.rep
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except:
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echo getCurrentExceptionMsg()
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