Quantum Tao

I wonder when Chinese sports analysts and reporters can be so frank or so mean to a player.

It will be a surprise if you see a Chinese sports analyst so harsh to  a player. But if it happens, maybe it means something good.

print "Please enter a temperature and scale (C or F): "
str = gets
exit if str.nil? or str.empty?
str.chomp!
temp, scale = str.split(" ")

abort "#{temp} is not a valid number." if temp !~ /-?d+/

temp = temp.to_f
case scale
  when "C", "c"
    f = 1.8*temp + 32
  when "F", "f"
    c = (5.0/9.0)*(temp-32)
else
  abort "Must specify C or F."
end

if f.nil?
  print "#{c} degrees Cn"
else
  print "#{f} degrees Fn"
end

In Ruby, variables do not have types, but the objects they refer to still have types. The simplest data types are character, numeric, and string.

There is a special kind of string worth mentioning, primarily useful in small scripts used to glue together larger programs. The command output string is sent to the operating system as a command to be executed, whereupon the output of the command is substituted back into the string. The simple form of this string uses the grave accent (sometimes called a back-tick or back-quote) as a beginning and ending delimiter; the more complex form uses the %x notation:

`whoami`
`ls -l`
%x[grep -i meta *.html | wc -l]

Regular expressions in Ruby look similar to character strings, but they are used differently. The usual delimiter is a slash character. (more…)

Variables and other identifiers normally start with an alphabetic letter or a special modifier. The basic rules are as follows:

Local variables (and pseudovariables such as self and nil) begin with a lowercase letter or an underscore.

Global variables begin with a $ (dollar sign).

Instance variables (within an object) begin with an @ (at sign).

Class variables (within a class) begin with two @ signs.

Constants begin with capital letters.

For purposes of forming identifiers, the underscore (_) may be used as a lowercase letter.

Special variables starting with a dollar sign (such as $1 and $/) are not dealt with here. (more…)