StandardPrelude.grace

#pragma NativePrelude
#pragma DefaultVisibility=public
inherits _prelude
var isStandardPrelude := true

class SuccessfulMatch.new(result', bindings') {
    inherits true
    def result = result'
    def bindings = bindings'
    method asString {
        "SuccessfulMatch(result = {result}, bindings = {bindings})"
    }
}

class FailedMatch.new(result') {
    inherits false
    def result = result'
    def bindings = []
    method asString {
        "FailedMatch(result = {result})"
    }
}

type Extractable = {
    extract
}
class BasicPattern.new {
    method &(o) {
        AndPattern.new(self, o)
    }
    method |(o) {
        OrPattern.new(self, o)
    }
}
class MatchAndDestructuringPattern.new(pat, items') {
    def pattern = pat
    def items = items'
    method match(o) {
        def m = pat.match(o)
        if (m) then{
            var mbindings := m.bindings
            def bindings = []
            if (mbindings.size < items.size) then {
                if (Extractable.match(o)) then {
                    mbindings := o.extract
                } else {
                    return FailedMatch.new(o)
                }
            }
            for (items.indices) do {i->
                def b = items[i].match(mbindings[i])
                if (!b) then {
                    return FailedMatch.new(o)
                }
                for (b.bindings) do {bb->
                    bindings.push(bb)
                }
            }
            SuccessfulMatch.new(o, bindings)
        } else {
            FailedMatch.new(o)
        }
    }
}

class VariablePattern.new(nm) {
    method match(o) {
        SuccessfulMatch.new(o, [o])
    }
}

class BindingPattern.new(pat) {
    method match(o) {
        def bindings = [o]
        def m = pat.match(o)
        if (!m) then {
            return m
        }
        for (m.bindings) do {b->
            bindings.push(b)
        }
        SuccessfulMatch.new(o, bindings)
    }
}

class WildcardPattern.new {
    method match(o) {
        SuccessfulMatch.new(done, [])
    }
}

class AndPattern.new(p1, p2) {
    method match(o) {
        def m1 = p1.match(o)
        if (!m1) then {
            return m1
        }
        def m2 = p2.match(o)
        if (!m2) then {
            return m2
        }
        def bindings = []
        for (m1.bindings) do {b->
            bindings.push(b)
        }
        for (m2.bindings) do {b->
            bindings.push(b)
        }
        SuccessfulMatch.new(o, bindings)
    }
}

class OrPattern.new(p1, p2) {
    method match(o) {
        if (p1.match(o)) then {
            return SuccessfulMatch.new(o, [])
        }
        if (p2.match(o)) then {
            return SuccessfulMatch.new(o, [])
        }
        FailedMatch.new(o)
    }
}

def _standardPrelude = self
def BasicGrace = object {
    method new {
        _prelude.clone(_standardPrelude)
    }
}
method new {
    _prelude.clone(self)
}