Differences

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--- at:tutorial:basic [2007/04/17 17:26] – tvcutsem
+++ at:tutorial:basic [2007/04/17 17:34] – tvcutsem
@@ Line 384: / Line 384: @@
 ==== 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>
 <booleanexpr>.ifTrue: { ...}
@@ Line 393: / Line 392: @@
 </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>
 >(0 < 1).ifTrue: { 0 }
@@ Line 407: / Line 406: @@
 </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>
-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>
+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.
 <code>