On Sep 15, 2007, at 1:51 AM, kendear wrote:

> i wonder in Ruby, is there a line method to do something like in C
>
>
> print_val("Array[3] + 1")
>
> and get the printout of
>
>
> Array[3] + 1 is 3.345

All you need is something like:

puts "myArray[3] + 1 is #{myArray[3] + 1} "

String interpolation. Great stuff.
Of course you have to create that array first to have something in it.

You could also do:

puts "myArray[3] + 1 is " + (myArray[3] + 1).to_s

Lots of ways, but the first one is most succinct.
Ruby is very flexible!
You can even go from this into a DSL with words that evaluate to
expressions.

On 15.09.2007 19:13, John Joyce wrote:
>
> On Sep 15, 2007, at 1:51 AM, kendear wrote:
>
>> i wonder in Ruby, is there a line method to do something like in C
>>
>>
>> print_val("Array[3] + 1")
>>
>> and get the printout of
>>
>>
>> Array[3] + 1 is 3.345

def print_val(expr,b=binding)
print( expr, " is ", eval(expr,b).inspect, "\n")
end

irb(main):026:0> a=%{foo bar baz}
=> "foo bar baz"
irb(main):027:0> print_val "a[1]", binding
a[1] is 111
=> nil
irb(main):028:0> print_val "a[1]"
NameError: undefined local variable or method `a' for main:Object
from (irb):21:in `print_val'
from (irb):21:in `print_val'
from (irb):28
from :0

You can even omit the "b" argument if you use something like
"Binding.of_caller".

Kind regards

robert