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named args for default predicate, custom predicates and dispatch targets #2

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34 changes: 22 additions & 12 deletions lib/multi_methods.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -10,51 +10,61 @@ def create_method( name, &block )
self.send( :define_method, name, block )
end


def defmulti method_name, default_dispatch_fn = nil
self.instance_variable_set( "@" + method_name.to_s, [] )

create_method( method_name ) do |*args|
def multimethod_exec callable, args_list
target = (callable.is_a? UnboundMethod) ? callable.bind(self) : callable
arity = target.arity
if arity == 0
target.call
elsif arity > 0
target.call(*args_list[0..arity-1])
elsif arity < 0
target.call(*args_list)
end
end
dispatch_table = self.class.instance_variable_get( "@" + method_name.to_s )

destination_fn = nil
default_fn = nil
default_dispatch_result = default_dispatch_fn.call(args) if default_dispatch_fn
default_dispatch_result = multimethod_exec(default_dispatch_fn, args) if default_dispatch_fn
dispatch_table.each do |m|
predicate = if m.keys.first.respond_to? :call
raise "Dispatch method already defined by defmulti" if default_dispatch_fn
m.keys.first
elsif m.keys.first == :default
default_fn = m.values.first
lambda { |args| false }
lambda { |*args| false }
else
lambda { |args| return default_dispatch_result == m.keys.first }
lambda { |*args| return default_dispatch_result == m.keys.first }
end

destination_fn = m.values.first if predicate.call(args)
destination_fn = m.values.first if multimethod_exec(predicate, args)
end

destination_fn ||= default_fn
raise "No matching dispatcher function found" unless destination_fn

if destination_fn.is_a? UnboundMethod
destination_fn.bind(self).call(args)
else
destination_fn.call(args)
end

multimethod_exec destination_fn, args
end
end

def defmethod method_name, dispatch_value, default_dispatch_fn
multi_method = self.instance_variable_get( "@" + method_name.to_s)
raise "MultiMethod #{method_name} not defined" unless multi_method
multi_method << { dispatch_value => default_dispatch_fn }
end
end #ClassMethods


module InstanceMethods

def defmulti_dirty &block
instance_eval &block
end

def defmulti_local &block
dispatch_return = instance_eval &block

Expand Down
79 changes: 65 additions & 14 deletions specs/multi_methods_spec.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -20,10 +20,10 @@ def tuna1 *args

def tuna_gateway *args
defmulti_local do
defmulti :tuna, lambda{ |args| args[0] + args[1] }
defmulti :tuna, lambda{ |*args| args[0] + args[1] }
defmethod :tuna, 2, self.class.instance_method(:tuna1)
defmethod :tuna, 4, self.class.method(:tuna2)
defmethod :tuna, :default, lambda{ |args| @default_fn = :tuna_default }
defmethod :tuna, :default, lambda{ |*args| @default_fn = :tuna_default }

tuna(*args)
end
Expand Down Expand Up @@ -64,13 +64,13 @@ def tuna_gateway *args
end
it "should raise an exception if trying to construct a defmethod without a previously defined defmulti of the same name" do
lambda do
@our_square.class.instance_eval { defmethod :chicken, lambda{ |args| args[0] }, instance_method(:chicken1) }
@our_square.class.instance_eval { defmethod :chicken, lambda{ |*args| args[0] }, instance_method(:chicken1) }
end.should raise_error( Exception, "MultiMethod chicken not defined" )
end

it "should raise an exception if no predicates match and there is no default defmethod" do
@our_square.class.instance_eval do
defmulti :chicken, lambda{ |args| args[1].class }
defmulti :chicken, lambda{ |*args| args[1].class }
defmethod :chicken, Fixnum, instance_method(:chicken1)
defmethod :chicken, String, method(:chicken2)
end
Expand All @@ -79,10 +79,10 @@ def tuna_gateway *args

it "should raise an exception if defining individual dispatch predicates AND a default dispatch fn" do
@our_square.class.instance_eval do
defmulti :chicken, lambda{ |args| args[1].class }
defmulti :chicken, lambda{ |*args| args[1].class }
defmethod :chicken, Fixnum, instance_method(:chicken1)
defmethod :chicken, String, method(:chicken2)
defmethod :chicken, lambda { |args| true }, lambda { |args| puts "never get here" }
defmethod :chicken, lambda { |*args| true }, lambda { |*args| puts "never get here" }
end
lambda do
@our_square.chicken(2)
Expand All @@ -97,7 +97,7 @@ def tuna_gateway *args
@our_square = Square.new

@our_square.class.instance_eval do
defmulti :chicken, lambda{ |args| args[1].class }
defmulti :chicken, lambda{ |*args| args[1].class }
defmethod :chicken, Fixnum, instance_method(:chicken1)
defmethod :chicken, String, method(:chicken2)
defmethod :chicken, :default, lambda { @dispatch_fn = :chicken_default; return :chicken_default }
Expand Down Expand Up @@ -142,7 +142,7 @@ def tuna_gateway *args
@our_square = Square.new

@our_square.class.instance_eval do
defmulti :chicken, lambda{ |args| args.size }
defmulti :chicken, lambda{ |*args| args.size }
defmethod :chicken, 1, instance_method(:chicken1)
defmethod :chicken, 2, method(:chicken2)
defmethod :chicken, :default, lambda { @dispatch_fn = :chicken_default}
Expand Down Expand Up @@ -184,8 +184,8 @@ def tuna_gateway *args

@our_square.class.instance_eval do
defmulti :chicken
defmethod :chicken, lambda{ |args| args[0].class == Fixnum && args[1].class == Fixnum }, instance_method(:chicken1)
defmethod :chicken, lambda{ |args| args[0].class == String && args[1].class == String }, method(:chicken2)
defmethod :chicken, lambda{ |*args| args[0].class == Fixnum && args[1].class == Fixnum }, instance_method(:chicken1)
defmethod :chicken, lambda{ |*args| args[0].class == String && args[1].class == String }, method(:chicken2)
defmethod :chicken, :default, lambda { @dispatch_fn = :chicken_default}
end

Expand Down Expand Up @@ -216,10 +216,10 @@ def tuna_gateway *args
it "should only be called if no other methods match" do
@our_square = Square.new
@our_square.class.instance_eval do
defmulti :puppy, lambda { |args| args[0] }
defmethod :puppy, 1, lambda { |args| :one }
defmethod :puppy, :default, lambda { |args| :default }
defmethod :puppy, 2, lambda { |args| :two }
defmulti :puppy, lambda { |*args| args[0] }
defmethod :puppy, 1, lambda { |*args| :one }
defmethod :puppy, :default, lambda { |*args| :default }
defmethod :puppy, 2, lambda { |*args| :two }
end

result = @our_square.puppy 2
Expand All @@ -228,4 +228,55 @@ def tuna_gateway *args
end
end

describe "arg splatting" do
before(:all) do
@our_square = Square.new
@our_square.class.instance_eval do
def glorb a, b=nil
[a, b]
end
defmulti :kitten, lambda { |a| a }
defmethod :kitten, 1, lambda { |a, b| [a,b] }
defmethod :kitten, 2, lambda { |a, b, c| [a,b,c] }
defmethod :kitten, 3, lambda { |a, b, c, d| [a,b,c,d] }
defmethod :kitten, 4, lambda { |*args| args.reverse }
defmethod :kitten, 5, method(:glorb)
defmethod :kitten, 6, lambda { |a, *rest| [a, rest] }
defmethod :kitten, :default, lambda { |*args| args }
end
end

it "should pass the number of args the lambda is expecting when it doesn't want a splatted list" do
@our_square.kitten(1,:b,:c,:d,:e,:f,:g).should == [1, :b]
@our_square.kitten(2,:b,nil,:d,:e,:f,:g).should == [2, :b, nil]
@our_square.kitten(3,:b,nil,[:d],:e,:f,:g).should == [3, :b, nil, [:d]]
@our_square.kitten(:guava,:b,:c,:d,:e,:f,:g).should == [:guava, :b, :c, :d, :e, :f, :g]
@our_square.kitten(5).should == [5, nil]
@our_square.kitten(5, :b).should == [5, :b]
end

it "should raise an argument exception if there are not enough arguments to satisfy the required args for a dispatch_fn" do
lambda { @our_square.kitten(1) }.should raise_error( Exception, "wrong number of arguments (1 for 2)" )
end

it "should not raise an argument exception if there are not enough arguments to satisfy optional args for a dispatch_fn" do
lambda { @our_square.kitten(5) }.should_not raise_error( Exception, "wrong number of arguments (1 for 2)" )
end

it "should raise an argument exception if there are too many arguments for a method" do
#NOTE: not sure why the exception is saying (3 for 1), :glorb takes 2 arguments, second is optional
lambda { @our_square.kitten(5,:b,:c) }.should raise_error(Exception, "wrong number of arguments (3 for 1)")
end

it "should pass the entire arg array when the lambda is expecting one splatted arg" do
@our_square.kitten(4,:b,:c,:d,:e,:f,:g).should == [4,:b,:c,:d,:e,:f,:g].reverse
end

it "should pass the correct number of args plus rest in the splatted args list when the dispatch_fn takes multiple args and a splatted arg" do
@our_square.kitten(6).should == [6,[]]
@our_square.kitten(6,:b,:c).should == [6, [:b, :c]]
end

end

end