ruby programming language(ch1-2)

Pre-study

rvm

If you need to separate configurations & gems for each ruby project individually, rvm is a good tool.

install check:

  • type -t rvm gives function

usage notes:

  • rvm install ruby <version>
  • rvm use <version> --default to set default ruby to use
  • rvm gemset use <group> and then gem install <gem> to install gem to that group
    • gems installed to global are inheritable

some tips:

  • make sure your term enable login-shell
  • source rvm at last as possible to avoid warning: ...path/to/ruby-bin not at first place in PATH...

pry

Interactive tool like bpython, i use pry --simple-prompt for convenient like noob test, etc.

ri

Ruby manual, e.g: ri Array, ri Array.sort, ri Hash#each, ri Math::sqrt.

Ch2

comments

1
# line comment
1
2
3
=begin
block comment
=end
  • there’s no /* */ like comment.
  • # is prior to =begin(end)

some symbol in identifiers

prefix/suffix:

  • $: global var
  • @: class instance var
  • @@: class var
  • xx?: boolean-valued method
  • xx!: in-place method
  • xx=: method invoked by assignment

reserved word:

  • __LINE__
  • __ENCODING__
  • __FILE__
  • __END__: after goes the data, you can refer these data by DATA

spaces

one line is implicitly closed if it’s a complete expression, check:

1
2
total = x +
y
1
2
total = x
+ y

after ruby1.9, newline start with . implicitly considered as continuel line, like chain-invoke:

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2
3
4
ani = Array.new
  .push("doge")
  .push("nya")
  .sort

ruby has grammar candy for method invoke, care the trap:

1
2
f(3+2)+1
f (3+2)+1

use ruby -w to check ambiguous warning.