mirror of
https://github.com/kanaka/mal.git
synced 2024-09-20 01:57:09 +03:00
8a19f60386
- Reorder README to have implementation list after "learning tool" bullet. - This also moves tests/ and libs/ into impls. It would be preferrable to have these directories at the top level. However, this causes difficulties with the wasm implementations which need pre-open directories and have trouble with paths starting with "../../". So in lieu of that, symlink those directories to the top-level. - Move the run_argv_test.sh script into the tests directory for general hygiene.
171 lines
4.7 KiB
Swift
171 lines
4.7 KiB
Swift
//******************************************************************************
|
|
// MAL - step 2 - eval
|
|
//******************************************************************************
|
|
// This file is automatically generated from templates/step.swift. Rather than
|
|
// editing it directly, it's probably better to edit templates/step.swift and
|
|
// regenerate this file. Otherwise, your change might be lost if/when someone
|
|
// else performs that process.
|
|
//******************************************************************************
|
|
|
|
import Foundation
|
|
|
|
// Parse the string into an AST.
|
|
//
|
|
private func READ(str: String) throws -> MalVal {
|
|
return try read_str(str)
|
|
}
|
|
|
|
// Perform a simple evaluation of the `ast` object. If it's a symbol,
|
|
// dereference it and return its value. If it's a collection, call EVAL on all
|
|
// elements (or just the values, in the case of the hashmap). Otherwise, return
|
|
// the object unchanged.
|
|
//
|
|
private func eval_ast(ast: MalVal, _ env: Environment) throws -> MalVal {
|
|
if let symbol = as_symbolQ(ast) {
|
|
guard let val = env.get(symbol) else {
|
|
try throw_error("'\(symbol)' not found") // Specific text needed to match MAL unit tests
|
|
}
|
|
return val
|
|
}
|
|
if let list = as_listQ(ast) {
|
|
var result = [MalVal]()
|
|
result.reserveCapacity(Int(list.count))
|
|
for item in list {
|
|
let eval = try EVAL(item, env)
|
|
result.append(eval)
|
|
}
|
|
return make_list(result)
|
|
}
|
|
if let vec = as_vectorQ(ast) {
|
|
var result = [MalVal]()
|
|
result.reserveCapacity(Int(vec.count))
|
|
for item in vec {
|
|
let eval = try EVAL(item, env)
|
|
result.append(eval)
|
|
}
|
|
return make_vector(result)
|
|
}
|
|
if let hash = as_hashmapQ(ast) {
|
|
var result = [MalVal]()
|
|
result.reserveCapacity(Int(hash.count) * 2)
|
|
for (k, v) in hash {
|
|
let new_v = try EVAL(v, env)
|
|
result.append(k)
|
|
result.append(new_v)
|
|
}
|
|
return make_hashmap(result)
|
|
}
|
|
return ast
|
|
}
|
|
|
|
// Walk the AST and completely evaluate it, handling macro expansions, special
|
|
// forms and function calls.
|
|
//
|
|
private func EVAL(ast: MalVal, _ env: Environment) throws -> MalVal {
|
|
|
|
if !is_list(ast) {
|
|
|
|
// Not a list -- just evaluate and return.
|
|
|
|
let answer = try eval_ast(ast, env)
|
|
return answer
|
|
}
|
|
|
|
// Special handling if it's a list.
|
|
|
|
let list = as_list(ast)
|
|
|
|
if list.isEmpty {
|
|
return ast
|
|
}
|
|
|
|
// Standard list to be applied. Evaluate all the elements first.
|
|
|
|
let eval = try eval_ast(ast, env)
|
|
|
|
// The result had better be a list and better be non-empty.
|
|
|
|
let eval_list = as_list(eval)
|
|
if eval_list.isEmpty {
|
|
return eval
|
|
}
|
|
|
|
// Get the first element of the list and execute it.
|
|
|
|
let first = eval_list.first()
|
|
let rest = as_sequence(eval_list.rest())
|
|
|
|
if let fn = as_builtinQ(first) {
|
|
let answer = try fn.apply(rest)
|
|
return answer
|
|
}
|
|
|
|
// The first element wasn't a function to be executed. Return an
|
|
// error saying so.
|
|
|
|
try throw_error("first list item does not evaluate to a function: \(first)")
|
|
}
|
|
|
|
// Convert the value into a human-readable string for printing.
|
|
//
|
|
private func PRINT(exp: MalVal) -> String {
|
|
return pr_str(exp, true)
|
|
}
|
|
|
|
// Perform the READ and EVAL steps. Useful for when you don't care about the
|
|
// printable result.
|
|
//
|
|
private func RE(text: String, _ env: Environment) -> MalVal? {
|
|
if !text.isEmpty {
|
|
do {
|
|
let ast = try READ(text)
|
|
do {
|
|
return try EVAL(ast, env)
|
|
} catch let error as MalException {
|
|
print("Error evaluating input: \(error)")
|
|
} catch {
|
|
print("Error evaluating input: \(error)")
|
|
}
|
|
} catch let error as MalException {
|
|
print("Error parsing input: \(error)")
|
|
} catch {
|
|
print("Error parsing input: \(error)")
|
|
}
|
|
}
|
|
return nil
|
|
}
|
|
|
|
// Perform the full READ/EVAL/PRINT, returning a printable string.
|
|
//
|
|
private func REP(text: String, _ env: Environment) -> String? {
|
|
let exp = RE(text, env)
|
|
if exp == nil { return nil }
|
|
return PRINT(exp!)
|
|
}
|
|
|
|
// Perform the full REPL.
|
|
//
|
|
private func REPL(env: Environment) {
|
|
while true {
|
|
if let text = _readline("user> ") {
|
|
if let output = REP(text, env) {
|
|
print("\(output)")
|
|
}
|
|
} else {
|
|
print("")
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
func main() {
|
|
let env = Environment(outer: nil)
|
|
|
|
load_history_file()
|
|
load_builtins(env)
|
|
|
|
REPL(env)
|
|
|
|
save_history_file()
|
|
}
|