lit_syntax_and_semantics

Syntax and Semantics

Comments

• Comments start with # character

# This is a comment.
# Support only one line.

Types

Bool

• Bool has two values

true 
false

Integers

• There is only 32 bit singed type

314
123456789

String

• A string literal starts with a double quote ( " ) and end in a double quote ( " )

"Hello world!"
"\n" # new line
"\t" # tab
"\'" # single quote
"\"" # double quote

Array

• An Array is created with only one type.
• An Array cannot have mixed types.

[1, 2, 3] #OK
["hello", "world!"] #OK
[1, "hello"] # NG

Local variables

• Local variables doesn't start with dollar sign ( $ )
• They are declared when first assignment.
• They are possible to specify types.

n = 10
str = "hello"
i:string = "hello" # specify
ary = [1, 2]

Global variables

• Global variables start with dollar sign ( $ )
• Under the circumstances, Global variables are not possible to specify types and support only Integer type...

$g = 10
$str = "hello" # impossible..

Control Syntax

If

• if evaluates the then branch if its condition is true, and evaluates the else or elsif branches.

i = 10
if i < 5
  i = 0
elsif i == 5
  i = 1
else
  i = 2
end
i # => 2 

While

• while executes the body while the conditon is true.

i = 0
while i < 10
 puts i
 i +=1
end

For

• for executes the body.

# First syntax (like C)
for i = 0, i < 10, i += 1
 puts i
end
# Second syntax (like Ruby)
for i in 0..9 # 0...10
 puts i
 # unnecessary increment
end

Break

• break breaks out of the loop

i = 0
while 1
 if i >= 5
  break
 end
 i +=1
end

Function

• Follow this to define the functions

def f(x) # parentheses may not need
	x + 1
end
def f x:string # support overload of function
	puts x
end
def f:string # set return type
	"hello"
end	
def add x:string y:string :string
	x + y
end
puts add "hel", "lo" # => hello

Standard Libraries

require

• require includes the specified file

require "std" # includes all stdlibs
require "Math" # library related to the Mathematics
require "File"

puts File::read "story.txt"
puts Math::sqrt 9.0 # => 3
puts length [1, 2, 3] # => 3
puts length "hello" # => 5