This document provides a summary of Ring documentation for version 1.5.1. It discusses defining variables before use, avoiding global variables, protecting class members, accessing object attributes and methods using 'this', pure functions that don't change state, first-class functions that can be passed as parameters and returned as values, higher-order functions that take other functions as parameters, anonymous and nested functions, and equality of functions.

1. Ring Documentation, Release 1.5.1
• Before defining any variable, Ring try to find the variable and use it if it’s found.
Note: Try to avoid the global variables, use the main function and start their names with $
Tip: In large programs protect your classes and define their members using self.attribute
39.14 Using This.Attribute and This.Method()
Inside class methods we have access to the object scope directly. we don’t need to use Self.attribute or Self.method to
read/write attribute and call methods.
But we can use braces {} while we are inside methods to access another object, In this case the current object scope
will be changed while we are inside the brace.
How we can get access to our class attributes and methods while we are inside braces?
This can be done using This.Attribute and This.Method()
Example:
new point
class point
x=10 y=20 z=30
print()
func print
new UI {
display(this.x,this.y,this.z)
}
Class UI
func display x,y,z
see x + nl + y + nl + z + nl
39.14. Using This.Attribute and This.Method() 265

2. CHAPTER
FORTY
FUNCTIONAL PROGRAMMING
In previous chapters we learned about Functions and Recursion.
In this chapter we are going to learn about more Functional Programming (FP) concepts like
• Pure Functions
• First-class functions
• Higher-order functions
• Anonymous and nested functions.
• Equality of functions
40.1 Pure Functions
We can create pure functions (functions that doesn’t change the state) by the help of the assignment operator to copy
variables (Lists & Objects) by value to create new variables instead of working on the original data that are passed to
the function by reference.
Example:
Func Main
aList = [1,2,3,4,5]
aList2 = square(aList)
see "aList" + nl
see aList
see "aList2" + nl
see aList2
Func Square aPara
a1 = aPara # copy the list
for x in a1
x *= x
next
return a1 # return new list
Output:
aList
1
2
3
4
5
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3. Ring Documentation, Release 1.5.1
aList2
1
4
9
16
25
40.2 First-class Functions
Functions inside the Ring programming language are first-class citizens, you can pass functions as parameters, return
them as value or store them in variables.
We can pass/return the function by typing the function name as literal like “FunctionName” or :FunctionName for
example.
We can pass/return functions using the variable that contains the function name.
We can call function from variables contains the function name using the Call command
Syntax:
Call Variable([Parameters])
Example:
Func Main
see "before test2()" + nl
f = Test2(:Test)
see "after test2()" + nl
call f()
Func Test
see "Message from test!" + nl
Func Test2 f1
call f1()
See "Message from test2!" + nl
return f1
Output:
before test2()
Message from test!
Message from test2!
after test2()
Message from test!
40.3 Higher-order Functions
Higher-order functions are the functions that takes other functions as parameters.
Example:
Func Main
times(5,:test)
40.2. First-class Functions 267

4. Ring Documentation, Release 1.5.1
Func Test
see "Message from the test function!" + nl
Func Times nCount,F
for x = 1 to nCount
Call F()
next
Output:
Message from the test function!
Message from the test function!
Message from the test function!
Message from the test function!
Message from the test function!
40.4 Anonymous and Nested Functions
Anonymous Functions are functions without names that can be passed as parameters to other functions or stored in
variables.
Syntax:
Func [Parameters] { [statements] }
Example:
test( func x,y {
see "hello" + nl
see "Sum : " + (x+y) + nl
} )
new great { f1() }
times(3, func { see "hello world" + nl } )
func test x
call x(3,3)
see "wow!" + nl
func times n,x
for t=1 to n
call x()
next
Class great
func f1
f2( func { see "Message from f1" + nl } )
func f2 x
call x()
Output:
hello
Sum : 6
40.4. Anonymous and Nested Functions 268

5. Ring Documentation, Release 1.5.1
wow!
Message from f1
hello world
hello world
hello world
Example:
Func Main
aList = [1,2,3,4]
Map (aList , func x {
return x*x
} )
see aList
aList = [4,9,14,25]
Map(aList, :myfilter )
see aList
aList = [11,12,13,14]
Map (aList , func x {
if x%2=0
return "even"
else
return "odd"
ok
})
see aList
Func myfilter x
if x = 9
return "True"
else
return "False"
ok
Func Map aList,cFunc
for x in aList
x = call cFunc(x)
next
Output:
1
4
9
16
False
True
False
False
odd
even
odd
even
40.5 Equality of functions
We can test if function = function or not using the ‘=’ or ‘!=’ operators
40.5. Equality of functions 269

6. Ring Documentation, Release 1.5.1
Example:
f1 = func { see "hello" + nl }
f2 = func { see "how are you?" + nl }
f3 = f1
call f1()
call f2()
call f3()
see (f1 = f2) + nl
see (f2 = f3) + nl
see (f1 = f3) + nl
Output:
hello
how are you?
hello
0
0
1
40.5. Equality of functions 270

7. CHAPTER
FORTYONE
REFLECTION AND META-PROGRAMMING
Since the Ring programming language is a dynamic language, we can get answers about the program code and we can
modify our code during the runtime.
In this chapter we will learn about this and the available functions to use.
41.1 locals() Function
We can get a list of variables names in the current scope using the locals() function.
Syntax:
locals() --> a list contains the variables names in the current scope
Example:
test("hello")
func test cMsg
see cMsg + nl
x = 10
y = 20
z = 30
see locals()
Output:
hello
cmsg
x
y
z
41.2 globals() Function
We can get a list of variables names in the global scope using the globals() function.
Syntax:
271

8. Ring Documentation, Release 1.5.1
globals() --> a list contains variables names in the global scope
Example:
x=10 y=20 z=30
test()
func test
see "message from test()" + nl +
"Global Variables:" + nl
see globals()
Output:
message from test()
Global Variables:
x
y
z
41.3 functions() Function
We can get a list of functions names written in the Ring language using the functions() function.
Syntax:
functions() --> a list contains functions names
Example:
see functions()
func f1
see "f1" + nl
func f2
see "f2" + nl
func f3
see "f3" + nl
Output:
f1
f2
f3
41.4 cfunctions() Function
We can get a list of functions names written in the C language using the cfunctions() function.
Syntax:
cfunctions() --> a list contains functions names
Example:
41.3. functions() Function 272

9. Ring Documentation, Release 1.5.1
aList = cfunctions()
See "Count : " + len(aList) + nl
for x in aList
see x + "()" + nl
next
Output:
Count : 197
len()
add()
del()
get()
clock()
...
Note: The complete list is removed from the previous output.
41.5 islocal() Function
We can check if a variable is defined in the local scope or not using the islocal() function.
Syntax:
islocal(cVariableName) --> returns 1 if the variable is defined in the local scope
returns 0 if the variable is not defined in the local scope
Example:
test()
func test
x=10 y=20
see islocal("x") + nl +
islocal("y") + nl +
islocal("z") + nl
Output:
1
1
0
41.6 isglobal() Function
We can check if a variable is defined in the global scope or not using the isglobal() function.
Syntax:
isglobal(cVariableName) --> returns 1 if the variable is defined in the global scope
returns 0 if the variable is not defined in the global scope
Example:
41.5. islocal() Function 273

10. Ring Documentation, Release 1.5.1
x=10 y=20
test()
func test
see isglobal("x") + nl +
isglobal("y") + nl +
isglobal("z") + nl
Output:
1
1
0
41.7 isfunction() Function
We can check if a Ring function is defined or not using the isfunction() function.
Syntax:
isfunction(cFunctionName) --> returns 1 if the Ring function is defined
returns 0 if the Ring function is not defined
Example:
see isfunction("f1") + nl +
isfunction("f2") + nl +
isfunction("f3") + nl
func f1
see "message from f1()" + nl
func f2
see "message from f2()" + nl
Output:
1
1
0
41.8 iscfunction() Function
We can check if a C function is defined or not using the iscfunction() function.
Syntax:
iscfunction(cFunctionName) --> returns 1 if the C function is defined
returns 0 if the C function is not defined
Example:
see iscfunction("len") + nl +
iscfunction("add") + nl +
iscfunction("test") + nl
41.7. isfunction() Function 274