types.swift

enum MalError: Error {
    case Reader(msg: String)
    case General(msg: String)
    case MalException(obj: MalVal)
}

class MutableAtom {
    var val: MalVal
    init(val: MalVal) {
        self.val = val
    }
}

enum MalVal {
    case MalNil
    case MalTrue
    case MalFalse
    case MalInt(Int)
    case MalFloat(Float)
    case MalString(String)
    case MalSymbol(String)
    case MalList(Array<MalVal>, meta: Array<MalVal>?)
    case MalVector(Array<MalVal>, meta: Array<MalVal>?)
    case MalHashMap(Dictionary<String,MalVal>, meta: Array<MalVal>?)
    // TODO: internal MalVals are wrapped in arrays because otherwise
    // compiler throws a fault
    case MalFunc((Array<MalVal>) throws -> MalVal,
                 ast: Array<MalVal>?,
                 env: Env?,
                 params: Array<MalVal>?,
                 macro: Bool,
                 meta: Array<MalVal>?)
    case MalAtom(MutableAtom)
}

typealias MV = MalVal

// General functions

func wraptf(_ a: Bool) -> MalVal {
    return a ? MV.MalTrue : MV.MalFalse
}


// equality functions
func cmp_seqs(_ a: Array<MalVal>, _ b: Array<MalVal>) -> Bool {
    if a.count != b.count { return false }
    var idx = a.startIndex
    while idx < a.endIndex {
        if !equal_Q(a[idx], b[idx]) { return false }
        idx = a.index(after:idx)
    }
    return true
}

func cmp_maps(_ a: Dictionary<String,MalVal>,
              _ b: Dictionary<String,MalVal>) -> Bool {
    if a.count != b.count { return false }
    for (k,v1) in a {
        if b[k] == nil { return false }
        if !equal_Q(v1, b[k]!) { return false }
    }
    return true
}

func equal_Q(_ a: MalVal, _ b: MalVal) -> Bool {
    switch (a, b) {
    case (MV.MalNil, MV.MalNil): return true
    case (MV.MalFalse, MV.MalFalse): return true
    case (MV.MalTrue, MV.MalTrue): return true
    case (MV.MalInt(let i1), MV.MalInt(let i2)): return i1 == i2
    case (MV.MalString(let s1), MV.MalString(let s2)): return s1 == s2
    case (MV.MalSymbol(let s1), MV.MalSymbol(let s2)): return s1 == s2
    case (MV.MalList(let l1,_), MV.MalList(let l2,_)):
        return cmp_seqs(l1, l2)
    case (MV.MalList(let l1,_), MV.MalVector(let l2,_)):
        return cmp_seqs(l1, l2)
    case (MV.MalVector(let l1,_), MV.MalList(let l2,_)):
        return cmp_seqs(l1, l2)
    case (MV.MalVector(let l1,_), MV.MalVector(let l2,_)):
        return cmp_seqs(l1, l2)
    case (MV.MalHashMap(let d1,_), MV.MalHashMap(let d2,_)):
        return cmp_maps(d1, d2)
    default:
        return false
    }
}

// list and vector functions
func list(_ lst: Array<MalVal>) -> MalVal {
    return MV.MalList(lst, meta:nil)
}
func list(_ lst: Array<MalVal>, meta: MalVal) -> MalVal {
    return MV.MalList(lst, meta:[meta])
}

func vector(_ lst: Array<MalVal>) -> MalVal {
    return MV.MalVector(lst, meta:nil)
}
func vector(_ lst: Array<MalVal>, meta: MalVal) -> MalVal {
    return MV.MalVector(lst, meta:[meta])
}


// hash-map functions

func _assoc(_ src: Dictionary<String,MalVal>, _ mvs: Array<MalVal>)
        throws -> Dictionary<String,MalVal> {
    var d = src
    if mvs.count % 2 != 0 {
        throw MalError.General(msg: "Odd number of args to assoc_BANG")
    }
    var pos = mvs.startIndex
    while pos < mvs.count {
        switch (mvs[pos], mvs[pos+1]) {
        case (MV.MalString(let k), let mv):
            d[k] = mv
        default:
            throw MalError.General(msg: "Invalid _assoc call")
        }
        pos += 2
    }
    return d
}

func _dissoc(_ src: Dictionary<String,MalVal>, _ mvs: Array<MalVal>)
        throws -> Dictionary<String,MalVal> {
    var d = src
    for mv in mvs {
        switch mv {
        case MV.MalString(let k): d.removeValue(forKey: k)
        default: throw MalError.General(msg: "Invalid _dissoc call")
        }
    }
    return d
}


func hash_map(_ dict: Dictionary<String,MalVal>) -> MalVal {
    return MV.MalHashMap(dict, meta:nil)
}

func hash_map(_ dict: Dictionary<String,MalVal>, meta:MalVal) -> MalVal {
    return MV.MalHashMap(dict, meta:[meta])
}

func hash_map(_ arr: Array<MalVal>) throws -> MalVal {
    let d = Dictionary<String,MalVal>();
    return MV.MalHashMap(try _assoc(d, arr), meta:nil)
}


// function functions
func malfunc(_ fn: @escaping (Array<MalVal>) throws -> MalVal) -> MalVal {
    return MV.MalFunc(fn, ast: nil, env: nil, params: nil,
                      macro: false, meta: nil)
}
func malfunc(_ fn: @escaping (Array<MalVal>) throws -> MalVal,
             ast: Array<MalVal>?,
             env: Env?,
             params: Array<MalVal>?) -> MalVal {
    return MV.MalFunc(fn, ast: ast, env: env, params: params,
                      macro: false, meta: nil)
}
func malfunc(_ fn: @escaping (Array<MalVal>) throws -> MalVal,
             ast: Array<MalVal>?,
             env: Env?,
             params: Array<MalVal>?,
             macro: Bool,
             meta: MalVal?) -> MalVal {
    return MV.MalFunc(fn, ast: ast, env: env, params: params,
                      macro: macro, meta: meta != nil ? [meta!] : nil)
}
func malfunc(_ fn: @escaping (Array<MalVal>) throws -> MalVal,
             ast: Array<MalVal>?,
             env: Env?,
             params: Array<MalVal>?,
             macro: Bool,
             meta: Array<MalVal>?) -> MalVal {
    return MV.MalFunc(fn, ast: ast, env: env, params: params,
                      macro: macro, meta: meta)
}

// sequence functions

func _rest(_ a: MalVal) throws -> Array<MalVal> {
    switch a {
    case MV.MalList(let lst,_):
        let start = lst.index(after: lst.startIndex)
        let slc = lst[start..<lst.endIndex]
        return Array(slc)
    case MV.MalVector(let lst,_):
        let start = lst.index(after: lst.startIndex)
        let slc = lst[start..<lst.endIndex]
        return Array(slc)
    default:
        throw MalError.General(msg: "Invalid rest call")
    }
}

func rest(_ a: MalVal) throws -> MalVal {
    return list(try _rest(a))
}

func _nth(_     a: MalVal, _ idx: Int) throws -> MalVal {
    switch a {
    case MV.MalList(let l,_): return l[l.startIndex.advanced(by: idx)]
    case MV.MalVector(let l,_): return l[l.startIndex.advanced(by: idx)]
    default: throw MalError.General(msg: "Invalid nth call")
    }
}