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Oleg Montak
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Nov 8, 2019
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,159 @@ | ||
| import Foundation | ||
| import core | ||
|
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| func read(_ s: String) throws -> Expr { | ||
| return try Reader.read(s) | ||
| } | ||
|
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| private func evalAst(_ expr: Expr, env: Env) throws -> Expr { | ||
| switch expr { | ||
| case let .symbol(name): | ||
| return try env.get(name) | ||
| case let .vector(values): | ||
| return .vector(try values.map { try eval($0, env: env) }) | ||
| case let .hashmap(values): | ||
| return .hashmap(try values.mapValues { try eval($0, env: env) }) | ||
| case let .list(ast): | ||
| return .list(try ast.map { try eval($0, env: env) }) | ||
| default: | ||
| return expr | ||
| } | ||
| } | ||
|
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| func eval(_ expr: Expr, env: Env) throws -> Expr { | ||
|
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| var env = env | ||
| var expr = expr | ||
|
|
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| while true { | ||
|
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| guard case let .list(ast) = expr else { | ||
| return try evalAst(expr, env: env) | ||
| } | ||
| if ast.isEmpty { | ||
| return expr | ||
| } | ||
|
|
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| switch ast[0] { | ||
|
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| case .symbol("def!"): | ||
| guard ast.count == 3 else { throw MalError.invalidArguments("def!") } | ||
| guard case let .symbol(name) = ast[1] else { throw MalError.invalidArguments("def!") } | ||
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| let val = try eval(ast[2], env: env) | ||
| env.set(forKey: name, val: val) | ||
| return val | ||
|
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| case .symbol("let*"): | ||
| guard ast.count == 3 else { throw MalError.invalidArguments("let*") } | ||
|
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| switch ast[1] { | ||
| case let .list(bindable), let .vector(bindable): | ||
| let letEnv = Env(outer: env) | ||
|
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| for i in stride(from: 0, to: bindable.count - 1, by: 2) { | ||
| guard case let .symbol(key) = bindable[i] else { throw MalError.invalidArguments("let*") } | ||
| let value = bindable[i + 1] | ||
| letEnv.set(forKey: key, val: try eval(value, env: letEnv)) | ||
| } | ||
|
|
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| expr = ast[2] | ||
| env = letEnv | ||
| default: | ||
| throw MalError.invalidArguments("let*") | ||
| } | ||
|
|
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| case .symbol("do"): | ||
| let exprsToEval = ast.dropFirst() | ||
| guard !exprsToEval.isEmpty else { throw MalError.invalidArguments("do") } | ||
| _ = try exprsToEval.dropLast().map { try eval($0, env: env) } | ||
| expr = exprsToEval.last! | ||
|
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| case .symbol("if"): | ||
| guard 3...4 ~= ast.count else { throw MalError.invalidArguments("if") } | ||
|
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| switch try eval(ast[1], env: env) { | ||
| case .bool(false), .null: | ||
| if let falseBranch = ast[safe: 3] { | ||
| expr = falseBranch | ||
| } else { | ||
| expr = .null | ||
| } | ||
| default: | ||
| expr = ast[2] | ||
| } | ||
|
|
||
| case .symbol("fn*"): | ||
| guard ast.count == 3 else { throw MalError("fn*") } | ||
| let binds: [String] | ||
|
|
||
| switch ast[1] { | ||
| case let .list(xs), let .vector(xs): | ||
| binds = try xs.map { | ||
| guard case let .symbol(name) = $0 else { throw MalError.invalidArguments("fn*") } | ||
| return name | ||
| } | ||
| default: | ||
| throw MalError.invalidArguments("fn*") | ||
| } | ||
|
|
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| let run: ([Expr]) throws -> Expr = { args in | ||
| let fEnv = try Env(binds: binds, exprs: args, outer: env) | ||
| return try eval(ast[2], env: fEnv) | ||
| } | ||
|
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| let f = Func(ast: ast[2], params: binds, env: env, run: run) | ||
| return .function(f) | ||
|
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| default: | ||
| guard case let .list(evaluatedList) = try evalAst(expr, env: env) else { fatalError() } | ||
| guard case let .function(fn) = evaluatedList[0] else { throw MalError("not a function: \(evaluatedList[0])") } | ||
|
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| let args = Array(evaluatedList.dropFirst()) | ||
| if let ast = fn.ast, let fnEnv = fn.env { | ||
| let newEnv = try Env(binds: fn.params, exprs: args, outer: fnEnv) | ||
| env = newEnv | ||
| expr = ast | ||
| } else { | ||
| return try fn.run(args) | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| func print(_ expr: Expr) -> String { | ||
| return Expr.print(expr) | ||
| } | ||
|
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| func rep(_ s: String, env: Env) -> String { | ||
| do { | ||
| let expr = try read(s) | ||
| let resExpr = try eval(expr, env: env) | ||
| let resultStr = print(resExpr) | ||
| return resultStr | ||
| } catch { | ||
| return error.localizedDescription | ||
| } | ||
| } | ||
|
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| let replEnv: Env = Env(data: Core.ns.data) | ||
|
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| replEnv.set(forKey: "eval", val: .function(Func { args in | ||
| guard let expr = args.first else { throw MalError.invalidArguments("eval") } | ||
| return try eval(expr, env: replEnv) | ||
| })) | ||
| replEnv.set(forKey: "*ARGV*", val: .list(CommandLine.arguments.dropFirst(2).map(Expr.string))) | ||
|
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| _ = rep("(def! not (fn* (a) (if a false true)))", env: replEnv) | ||
| _ = rep(#"(def! load-file (fn* (f) (eval (read-string (str "(do " (slurp f) "\nnil)")))))"#, env: replEnv) | ||
|
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| if CommandLine.arguments.count > 1 { | ||
| _ = rep("(load-file \"" + CommandLine.arguments[1] + "\")", env: replEnv) | ||
| exit(0) | ||
| } | ||
|
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| while true { | ||
| print("user> ", terminator: "") | ||
| guard let s = readLine() else { break } | ||
| print(rep(s, env: replEnv)) | ||
| } |