RichardOnRails
11/23/2006 2:12:00 AM
Below is my "show" method followed by some tests. I envision using
something like this to produce a tutorial for myself. Examples 1 & 2
demonstrate that "show" accepts a source code string and then displays
the source code followed by the result one would obtain by executing
that code in a stand-alone environment.
But Example #3 does not transmit elements of string (identified by a
pattern) to a succeeding string. However, Example #4 demonstrates that
code in #3 (even with an abstraction for the number of digits) works
fine outside of "eval".
Is this problem the result of a limitation in eval, or is the a way to
code it so it works?
====== results =========
>ruby Test1.rb
a=2; b=3; a*b
=> 6
hrs=24;
mins=60;
"mins/day = " + (hrs*mins).to_s
=> mins/day = 1440
require 'bigdecimal'
require 'bigdecimal/math'
include BigMath
BigMath::PI(6).to_s =~ /.(.)(.)(.{5})/
"result = " + ""
=> result =
Pi = 3.14159 (to 6 significant digits)
>Exit code: 0
======= code =========
def show(stmt)
puts stmt
puts "=> " + eval(stmt).to_s
puts
end
#1: Works great
show("a=2; b=3; a*b")
#2: Works great, too
show(%Q@
hrs=24;
mins=60;
"mins/day = " + (hrs*mins).to_s
@)
#3: Can't find the elements of the match
show(%Q@require 'bigdecimal'
require 'bigdecimal/math'
include BigMath
BigMath::PI(6).to_s =~ /.(.)(.)(.{5})/
"result = " + "#{$2}#{$1}#{$3}"
@)
#4: But this can find them just fine:
require 'bigdecimal'
require 'bigdecimal/math'
include BigMath
n=6
BigMath::PI(n).to_s =~ /.(.)(.)(.{#{n-1}})/
puts "Pi = #{$2}#{$1}#{$3} (to #{n} significant digits)"