I have the body of a ruby function as a string like
s = "x + 1"
I would like to do something like
fn = make_function(:x, s)
y = fn(10) # returns 11
What is the best way to achieve something like this?
Note that I'd rather not just keep eval'ing the string for each function call
This will eval the string once to define the function.
eval ['def fn(x)', s, 'end'].join("\n")
Here's something like your desired make_function
def make_function(klass, name, args, body)
args = [ args ].flatten.map(&:to_s).join(', ')
klass.class_eval ["def #{name} (#{args})", body, 'end'].join("\n")
end
irb> make_function(Object,:foo,[:x],'x*2')
=> nil
irb> foo(10)
=> 20
irb> foo(1.3)
=> 2.6
eval a Proc!
def make_function(arguments, body)
eval "Proc.new { |#{arguments}
#{body}
}"
end
f = make_function :x, 'x + 1'
puts f.call 10 # 11
puts f.call 21 # 22
You really DO NOT WANT TO DO THIS. But it works as you wanted nevertheless.
module Kernel
def make_function(*args, string)
method_name = args.shift
parameters = args
args_string = parameters.map{|p| p.to_s}.join(",")
instance_eval <<-RUBY
def #{method_name}(#{args_string})
#{string}
end
RUBY
end
end
s = "x + 1"
make_function(:fn,:x,s)
puts fn(1) #=> 2
s2 = "x + y"
make_function(:foo,:x, :y,s2)
puts foo(1,5) #=> 2
