= Cobra Differences From C# =

== Illustrated ==

{{{
#!cobra
# Cobra
d = {'a': 1, 'b': 2}
assert d['a'] == 1 and d['b'] == 2
for key, value in d
    print '[key] = [value]'  # string interpolation
}}}

{{{
// C#
var dictionary = new Dictionary<string, int> { {"a", 1}, {"b", 2} };
Assert.IsTrue(dictionary["a"] == 1 && dictionary["b"] == 2);
foreach (var key in dictionary.Keys)
{
   var value = dictionary[key];
   Debug.WriteLine(string.Format("{0} == {1}", key, value));
}
}}}

credit: http://fir3pho3nixx.blogspot.com/2011/01/when-c-is-not-enough.html


== Quick Reference ==

 * Dynamic Typing and Type inference (doesnt require Type or keyword to declare locals)
     * optional type declarations
 * Block structured by indentation only (like Python) no squiggly braces (brackets)
  * nil tracking - variables can be declared as nil assignable (or not)
 * Built in language support for 
    * unit test code 
    * assertions
    * Design by contract - invariants, preconditions and postconditions
 * Syntax support for builtin
     * Lists - [] - List of Dynamic
     * Dictionaries - {:} Dictionary of <Dynamic, Dynamic>
     * Sets - {,}  
 * Line Oriented 
     * '''#''' to comment line (instead of //)
     * '''/# ... #/''' for multiline comments
     * Line continuation is implied in method argument lists: foo.bar(arg1,[NEWLINE]arg2)
     * Use a trailing '''_''' for explicit line continuation
     * Tab or 4 Spaces to indent line (Fixed 4 space indent), Cannot mix Tabs and spaces for an indent level
     * No statement terminator (goodbye to ';')
 * Fractional numbers default to decimal type (rather than int)- can be overridden (to float/double) with a compiler
   commandline option

 * Method names and properties start with lowercase. (i.e lowerCamelCase)
    * Access to methods/properties in used libraries are also done via (implicitly mapped) lowerCamelCase methodnames
    * In resulting binaries such as .exe and .dll, the .NET standard CamelCase is used so that Cobra libraries vend out naturally to C# and VB.NET 
 * Class names must be (upper) [http://en.wikipedia.org/wiki/CamelCase CamelCased] or at least start with an upper case letter)
 * instance variable optionally prefixed with _ (implicitly makes them protected) or __ (implicitly makes them private. 
   If so prefixed can be accessed directly in methods (without a leading '.')
 * methods (and properties) on current object invoked with leading '''this.''' or more usually (shortcut) just '''.'''.
 * constructor/initializer method is called init, has no return value
 
 * String type accessed as '''String''' 
 * Numeric types specified as int, uint, float/float64, float32 and decimal
 * Sized int and uint types all have the same naming form
    * int8, int16, int/int32, int64 instead of  SByte, Int16, Int32/int, Int64
    * uint8, uint16, uint/uint32, uint64  instead of Byte, UInt16, ... 
    * float32, float/float64 instead of float, double
 * Type of numeric literals can be dictated using suffixes

 * Variable specification - typing, access modifiers, argument attributes  specified by keyword '''as''' rather than C-like/Java-like syntax
    * e.g. x as int32, instVar as string public  (vs int32 x;   public String instVar; )
 * typecasting by keyword '''to''' as in 'x to Type' rather than '(Type)x'
    * cast to and away from nilable Type.
 * '''is shared''' to declare a static type


 * '''<>''' instead of '''!=''' for 'not equals' comparisons
 * Condition negation uses keyword '''not'''  ( as in {{{ not a >10}}} )
 * boolean conditions use keywords '''and''' and '''or'''  ( as in {{{ if a>3 and b<10 or b>55 }}})
 * boolean '''and''' and '''or''' have equal precedence in Cobra whereas in C# they are differentiated. When converting code to Cobra, additional parentheses may be needed.
 * '''nil''' for no object (null) value
 * Supports +=, -=, etc. Does not support ++ or -- unary operators ( use += 1 and -= 1 instead).
 
 * boolean conditions can be tested on any type. True is any of
    * non false (bool Type)
    * numeric not 0
    * non zero char
    * not nil
 * blank strings and empty collections are true (non nil) - must check .length for strings and .count for collections

 * Strings delimited by single or double quotes, normal range of \c expansion ( e.g \n, \t)
 * Substitute expressions (values) directly in strings by enclosing with [].
    * such expressions can have optional String.format specification
 * 'Raw' Strings (r"a raw string") no escape sequence expansion ( vs c# @"a raw string")
 * '!NoSubstitution' strings ( ns" no substitution [done] here") 
 * !DocStrings on Programs, Classes, Interfaces (etc), instance variables, methods and properties
 * Different syntax for characters c'x'
 * since '[] used for declaring literal Lists, array literals are specified using ''' @[]''' - comma separated values
 * '''ref''' keyword for getting a reference (e.g., safe pointer) to a method, rather than calling it, so the reference can be stored or passed around. (for delegates)
 * '''sig''' keyword for declaring a delegate type

 * '''def''' keyword to declare a method/function
    *  e.g def doCalc( start as int) as int    instead of   int doCalc( int start)
 * '''use''' keyword instead of 'using' to get access to a non default namespace
 * ''' branch... on, on, [else]''' statement rather than c# '''case''' statement 

 * Slicing syntax for sequences (Lists and Strings) [start:stop:step] as well as normal library subsequence methods (substring, range, ...)
 * numeric for loop uses slice syntax. e.g. for i in 1:10:1  vs for( int i =1; i<=10; i++)
 * the Cobra ternary operator has a different syntax: {{{if(<condition>, <texpr>, <fexpr>)}}}. Example at http://cobra-language.com/docs/manual/expressions/if.html


 * more as they surface

== See also ==

 * [http://cobra-language.com/forums/viewtopic.php?f=4&t=15 Cobra Forums Differences with C#]
 * http://cobra-language.com/how-to/