Datasheet

Little to nothing gets lost in translation. But the fact that the computer doesn’t
run your original code makes a difference in the way you think about the
development cycle. The immediate, hands-on feeling of an interpreted lan-
guage gives an extra lift to the agile development mindset.
Ruby is reflective
A Ruby program can reflect upon its own code, like a philosopher reflecting
on his or her own life. More specifically, a Ruby program can turn a string of
characters into executable code and can do this somersault during the run of
a program. Listing 1-1 contains an example:
Listing 1-1: Defining a Database Table
print “Enter some text: “
STDOUT.flush
text_input = gets
puts
print “You entered: “
print text_input
puts
print “Maybe you entered some Ruby code!\n”
print “I’ll try to execute the text that you entered.\n”
print “The result of executing your text is “
eval text_input
Figures 1-1 and 1-2 show two different runs of the code in Listing 1-1. In each
run the code prompts you to type some text. Ruby does two things with
whatever text you type:
 Ruby echoes the text (displays the text a second time on the screen).
 Ruby interprets your text as Ruby code and executes the code if possible.
The second step (reinterpreting text as code) is difficult to do in other pro-
gramming languages. Ruby makes it easy to reinterpret text as code, and this
ease makes life better for computer programmers.
Figure 1-1:
A run of the
code in
Listing 1-1.
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Part I: Nuts and Bolts
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