Curly bracket programming language

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Curly brace or bracket programming languages are those which use balanced brackets ({ and }, also known as "brace brackets" or simply "braces") to make blocks in their syntax or formal grammar, mainly due to being C-influenced.

Contents 1 History 2 Statements and blocks 2.1 Loops 2.2 Conditional statements 2.3 Exception handling 2.4 Problems 3 Languages

[edit] History

Curly-bracket style goes way back before C. BCPL was the first language to use a curly bracket style, for outlining multi-statement function bodies. Ken Thompson gave the feature more glory in B. Because C was initially designed after B, C has retained the bracket style of B. Many languages that came after C (C++, Java, JavaScript and its generalized standard ECMAScript, C#, D, etc.) keep the style. Pico is a non-C descendant that also uses this style.

One common part of curly bracket style is the common style of terminating a statement with a semicolon (;), which is one way for languages to ignore whitespace. BCPL and Pico, do not have this rule. Thus a newline is used as a statement terminator in such languages. The Pico indent style is then used, as below (BCPL):

LET FUNC foo(a) = VALOF
{ b := a + 1
  RESULTIS b }

[edit] Statements and blocks

The name derives from the common syntax of the languages, where blocks of statements are enclosed in curly brackets. For example (using BSD/Allman indent style, one of many stylistic ways to format a program):

for (int i = 0; i < 10; i++)
{
    printf("%d", i);
    doTask(i);
}

Languages in this family are sometimes referred to as C-style, because they tend to have syntax that is strongly influenced by C syntax. Beside the curly brackets, they often inherit other syntactic features, such as using the semicolon as a statement terminator (not as a separator), and the three-part "for" statement syntax as shown above.

Generally, these languages are also considered "free-form languages", meaning that the compiler considers all whitespace to be the same as one blank space, much like HTML. Considering that, the above code could be written:

for(int i=0;i<10;i++){printf("%d",i);doTask(i);}

but this is not recommended, as it becomes nearly impossible for a person to read after the program grows beyond a few statements.

A popular way to work with curly braces is with the K&R style:

int i;
for(i = 0; i < 10; i++) {
   printf("%d", i);
   doTask(i);
}

There are many other ways to identify statement blocks, such as ending keywords that may match beginning keywords (in Ada, Pascal, REXX, and Visual Basic), the Off-side rule of indentation (in Python), or other symbols such as parentheses (in Lisp). These ways are not necessarily exclusive: whereas indentation is the default in Haskell, curly brackets can be used when desired.

[edit] Loops

In C, C++, C#, and Java:

while (boolean expression)
{
    statement(s)
}

do
{
    statement(s)
} while (boolean expression);

for (initialisation; termination condition; incrementing expr)
{
    statement(s)
}

[edit] Conditional statements

In C, C++, C#, and Java:

if (boolean expression)
{
    statement(s)
}

if (boolean expression)
{
    statement(s)
} 
else
{
    statement(s)
}

if (boolean expression)
{
    statement(s)
} 
else if (boolean expression)
{
    statement (s)
}
...
else
{
    statement(s)
}

switch (integer expression)
{
    case constant integer expr:
        statement(s)
        break;
    ...
    default:
        statement(s)
        break;
}

[edit] Exception handling

In C++, C# and Java:

try
{
    statement(s)
}
catch (exception type)
{
    statement(s)
}
catch (exception type)
{
    statement(s)
}
finally
{
    statement(s)
}

Objective-C has the same syntax starting with gcc 3.3 and Apple Mac OS X 10.3 , but with an at sign in front of the keywords (@try, @catch, @finally).

C++ does not have finally, but otherwise looks similar. C has nothing like this, though some compilers vendors added the keywords __try and __finally to their implementation.

[edit] Problems

Some 7 bit national ISO646 sets redefine curly brackets to characters that make programs hardly readable on such designed terminals. For example, the YUSCII set used in Yugoslavia redefines '{' as 'š', while '}' is redefined to 'ċ'. To address this problem, ANSI C introduced trigraphs that can be used instead of such problematic characters. All trigraphs consist of two question marks (“??”) followed by a character that is not redefined in the national 7 bit ASCII character sets. The trigraphs for ‘{’ and ‘}’, respectively, are “??<” and “??>”.

[edit] Languages

• ABCL/c+
• Alef
  • Limbo
• AutoHotkey
• AWK
• C - developed circa 1970 at Bell Labs
• C shell (csh)
• C++
• C#
• Ch - embeddable C/C++ interpreter
• ChucK - for audio programming
• Cilk - concurrent C for multithreaded parallel programming
• Coyote - C variant intended to lower the likelihood of some common errors, for example, buffer overflows
• Cyclone - C variant
• D - C/C++ inspired
• DINO
• E
• ECMAScript, variants: ActionScript, DMDScript, JavaScript, JScript
• Ferite
• Frink
• ICI
• Java
  • Groovy
  • Join Java
  • X10
• Objective-C
• Perl
• PHP
• Pico
• Pike
• rc
• TSL
• UnrealScript
• Windows PowerShell
• Yorick