Ambient-Oriented Programming

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at:tutorial:basic [2007/04/17 17:23] – tvcutsemat:tutorial:basic [2007/07/18 11:29] – elisag
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-<note> +
-**This Tutorial is still under heavy construction!!** +
-</note>+
 ====== Functional and Imperative Programming ====== ====== Functional and Imperative Programming ======
    
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 </code> </code>
  
-<note>+<note important>
 When using the '':='' assignment operator, beware of the following syntactic annoyance: the expression ''a := 1'' denotes an assignment to the variable ''a'', while ''a:= 1'' is misunderstood by the parser as ''a: = 1'', which is the invocation of a keyworded message named ''a:''. Keyworded message sends will be explained later on in this chapter. Hence, as a general rule, don't forget to always put a space between the variable name and the '':='' operator. When using the '':='' assignment operator, beware of the following syntactic annoyance: the expression ''a := 1'' denotes an assignment to the variable ''a'', while ''a:= 1'' is misunderstood by the parser as ''a: = 1'', which is the invocation of a keyworded message named ''a:''. Keyworded message sends will be explained later on in this chapter. Hence, as a general rule, don't forget to always put a space between the variable name and the '':='' operator.
 </note> </note>
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 >def [get, set] := makeCell(42); >def [get, set] := makeCell(42);
 >>[<closure:getter>, <closure:setter>] >>[<closure:getter>, <closure:setter>]
 +>get();
 +>>42
 </code> </code>
  
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    def total := a + b;     def total := a + b; 
    foreach: { |el| total := total + el} in: rest; total     foreach: { |el| total := total + el} in: rest; total 
- }; sum(1,2,3)+ }; 
 +>><closure:lambda>  
 +>sum(1,2,3)
 >>6 >>6
 </code> </code>
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 ==== Numerical data types ==== ==== Numerical data types ====
  
-AmbientTalk supports numbers and fractions which represent what other languages call integers and floating point numbers, respectively.  +AmbientTalk supports numbers and fractions which represent what other languages call integers and double precision floating point numbers, respectively.
  
-Note that since numerical types are objects in AmbientTalk, the traditional operators +,-,*,/, >, <, <=, >=, =, !=  are nothing but syntactic sugar for method invocations. Therefore,  //1+1// is internally translated into //1.+(1)//. Unary operators are just applications, e.g. //-5// is internally translated into //-(5)//. What follows are some basic examples of manipulations with numeric types:+Note that since numerical types are objects in AmbientTalk, the traditional operators %%+,-,*,/, >, <, <=, >=, =, !=%%  are nothing but syntactic sugar for method invocations. Therefore,  ''1+1'' is internally translated into ''1.+(1)''. Unary operators are just applications, e.g. ''-5'' is internally translated into ''-(5)''. What follows are some basic examples of manipulations with numeric types:
 <code> <code>
 >1.inc() >1.inc()
 >>2 >>2
->-1.abs() 
->>1 
 >1.cos() >1.cos()
 >>0.5403023058681398 >>0.5403023058681398
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 >>2 >>2
 </code> </code>
 +
 +Beware of the precedence rules for function application versus method invocation, which may lead to unexpected results, e.g.:
 +<code>
 +>-1.abs()
 +>>-1
 +</code>
 +This code is interpreted as ''-(1.abs())'', hence the result.
  
 Numbers also support some useful iterator methods such as: Numbers also support some useful iterator methods such as:
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 ==== Booleans ==== ==== Booleans ====
    
- +As any native type, booleans are objects so, they respond to keyword messages such as:
-AmbientTalk supports infix operators for booleans as &, | and !. As any native type, booleans are objects so, they respond to keyword messages such as:+
 <code> <code>
 <booleanexpr>.ifTrue: { ...}  <booleanexpr>.ifTrue: { ...} 
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 </code> </code>
  
-**=** and **!=** are the infix operators for equality and inequality. **true** and **false** are the boolean constant objects. What follows is some basic examples of boolean manipulation:+''='' and ''!='' are the infix operators for equality and inequality. The prefix operator ''!'' represents logical negation. ''true'' and ''false'' are the prototypical boolean singleton objects. What follows is some basic examples of boolean manipulation:
 <code> <code>
 >(0 < 1).ifTrue: { 0 }  >(0 < 1).ifTrue: { 0 } 
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 >>1 >>1
 > def [i, j] := [1,3] > def [i, j] := [1,3]
->>>[1, 3]+>>[1, 3]
 >{i < j}.whileTrue: { system.println(i); i := i + 1 } >{i < j}.whileTrue: { system.println(i); i := i + 1 }
 1 1
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 </code> </code>
  
-Boolean infix operators such as & and | are not shortcut. Thus, both arguments will be evaluated. For lazy evaluation, you should use the natives methods. For example, false.and: { 1/0 } will return false without executing the second argument.+Compound boolean expressions can be created by means of a boolean's ''and:'' and ''or:'' methods, which both take a zero-argument closure as argument. For example, ''false.and: { 1/0 }'' will return ''false''. The block is not applied because a logical //and// with ''false'' always fails.
  
-===== Control Flow Structures =====+===== Control Flow Constructs =====
  
-Control flow structures are defined in the lexical root of AmbientTalk. The lexical root is an object containing globally visible native methods. We have already seen in the previous sections examples of usage of the foreach and if/then structures. The complete list of traditional control flow structures defined in AmbientTalk is shown below:+Control flow constructs are defined in the lexical root of AmbientTalk. The lexical root is an object containing globally visible native methods (i.e. it is the top-level environment). We have already seen in the previous sections examples of use of the foreach and if/then structures. A list of traditional control flow structures defined in AmbientTalk is shown below:
 <code> <code>
-if: booleanCondition then: { consequent } +if: booleanCondition then: consequent 
-if: booleanCondition then: { consequent } else: { alternative } +if: booleanCondition then: consequent else: alternative 
-while: { condition } do: { body } +while: condition do: body 
-foreach: { |v| body } in: [ table ] +foreach: iteratorclosure in: table 
-do: { body } if: condition +do: body if: condition 
-do: { body } unless: condition+do: body unless: condition
 </code> </code>
 +
 +Note that ''condition'' in the ''while:do:'' construct denotes a //closure// that should return a boolean value. It needs to be a closure because the code is evaluated repeatedly until the closure returns false. ''body'', ''consequent'', ''alternative'' all denote zero-argument closures.
 +
 An example of usage for some of these structures is shown below in the definition of the sort function. An example of usage for some of these structures is shown below in the definition of the sort function.
 <code> <code>
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 >>[2, 4, 5, 6, 8, 37] >>[2, 4, 5, 6, 8, 37]
 </code> </code>
 +
 +AmbientTalk has no ''return'' statement. To achieve a similar jump in the control flow, see the section on [[:at:tutorial:modular#escaping_continuations|escaping continuations]].
at/tutorial/basic.txt · Last modified: 2020/02/09 22:05 by elisag