Cobra Differences From C#

Illustrated

# 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)  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 pointer to method (reference) rather than calling it (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

•  Cobra Forums Differences with C#
•  http://cobra-language.com/how-to/