at:tutorial:basic
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at:tutorial:basic [2007/04/17 17:34] – tvcutsem | at:tutorial:basic [2020/02/09 22:03] – elisag | ||
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- | < | ||
- | **This Tutorial is still under heavy construction!!** | ||
- | </ | ||
====== Functional and Imperative Programming ====== | ====== Functional and Imperative Programming ====== | ||
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</ | </ | ||
- | < | + | < |
When using the '': | When using the '': | ||
</ | </ | ||
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>>[1, [1, 2, [" | >>[1, [1, 2, [" | ||
</ | </ | ||
+ | |||
==== Table Splicing ==== | ==== Table Splicing ==== | ||
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>>[2, 3, 4] | >>[2, 3, 4] | ||
</ | </ | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | ==== Multidimensional Tables ==== | ||
+ | |||
+ | As mentioned before, there is no special constructor for definition of multidimensional tables, a table entry can contain another table. In what follows we have a closer look to manipulations with multidimensional tables. | ||
+ | |||
+ | < | ||
+ | def a := [[1,0,0], [0,1,0], [0,0,1]]; | ||
+ | >> | ||
+ | >a[1][2] | ||
+ | >>0 | ||
+ | >a[1] | ||
+ | >>[1, 0, 0] | ||
+ | > | ||
+ | >>3 | ||
+ | >a | ||
+ | >> | ||
+ | </ | ||
+ | |||
+ | An implicit definition of the same table can be expressed as follows: | ||
+ | |||
+ | < | ||
+ | def i := 0; | ||
+ | def aux[3] {0}; | ||
+ | def b[3] { i := i + 1; aux := [0,0,0]; aux[i] :=1; aux}; | ||
+ | >> | ||
+ | </ | ||
+ | |||
+ | You can find later in this chapter a helper function for creating matrices | ||
+ | |||
+ | |||
===== Functions ===== | ===== Functions ===== | ||
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</ | </ | ||
- | In that case, the //sum// function still accepts an arbitrary number of arguments as long as two arguments are supplied. //a// and //b// are considered as mandatory arguments of the argument list. | + | In that case, the //sum// function still accepts an arbitrary number of arguments as long as two arguments are supplied. //a// and //b// are considered as mandatory arguments of the argument list. |
+ | |||
+ | The splice operator can also be used to transform a table into an argument list for a function, for example: | ||
+ | < | ||
+ | def args := [3,4,5]; | ||
+ | > sum(1,2, @args); | ||
+ | >> 15 | ||
+ | </ | ||
+ | |||
+ | One way to think about this is that the splice operator splices the '' | ||
+ | < | ||
+ | > sum(1, | ||
+ | >> 21 | ||
+ | </ | ||
+ | |||
+ | |||
+ | |||
+ | |||
+ | |||
+ | ==== Optional Parameters ==== | ||
A function can also declare optional arguments as shown below. Optional arguments can be omitted in a function call. If this is the case, the default expression provided in their definition is evaluated and passed as argument to the function instead. | A function can also declare optional arguments as shown below. Optional arguments can be omitted in a function call. If this is the case, the default expression provided in their definition is evaluated and passed as argument to the function instead. | ||
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</ | </ | ||
- | As is customary in languages with the above parameter passing semantics, AmbientTalk requires mandatory parameters to be defined //before// optional parameters, which should in turn be defined //before// a variable-argument parameter, if any. | + | As is customary in languages with the above optional arguments, AmbientTalk requires mandatory parameters to be defined //before// optional parameters, which should in turn be defined //before// a variable-argument parameter, if any. |
+ | |||
+ | Let us show how to use optional arguments to define an auxilary function that creates matrices: | ||
+ | |||
+ | < | ||
+ | def makeMatrix(n, | ||
+ | def [i,j] := [0,0]; | ||
+ | def makeCol(i, | ||
+ | def col[m] { j := j + 1; init(i,j) } | ||
+ | }; | ||
+ | def matrix[n] { i := i + 1; makeCol(i, | ||
+ | }; | ||
+ | >def c := makeMatrix(3); | ||
+ | >> | ||
+ | >c[1] := [1,2,3] | ||
+ | >>[1, 2, 3] | ||
+ | >c | ||
+ | >> | ||
+ | >def d := makeMatrix(4, | ||
+ | >> [[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]] | ||
+ | </ | ||
===== Closures ===== | ===== Closures ===== | ||
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>def [get, set] := makeCell(42); | >def [get, set] := makeCell(42); | ||
>> | >> | ||
+ | >get(); | ||
+ | >>42 | ||
</ | </ | ||
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def total := a + b; | def total := a + b; | ||
| | ||
- | }; sum(1,2,3) | + | }; |
+ | >>< | ||
+ | >sum(1,2,3) | ||
>>6 | >>6 | ||
</ | </ | ||
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AmbientTalk borrows its block syntax from languages like Smalltalk and Self, where the role of the curly braces is played by square brackets, i.e. '' | AmbientTalk borrows its block syntax from languages like Smalltalk and Self, where the role of the curly braces is played by square brackets, i.e. '' | ||
</ | </ | ||
+ | |||
+ | |||
===== Keywords ===== | ===== Keywords ===== | ||
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def i := 0; | def i := 0; | ||
def mapped[tbl.length] { | def mapped[tbl.length] { | ||
- | | + | i := i+1; |
+ | clo( tbl[ i ] ) | ||
}; | }; | ||
} | } | ||
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</ | </ | ||
- | However, it is impossible | + | It is also possible |
+ | |||
+ | < | ||
+ | foo: | ||
+ | </ | ||
+ | |||
+ | <note important> | ||
+ | Be careful when nesting calls to keyworded functions: | ||
+ | </ | ||
===== Native Data Types ===== | ===== Native Data Types ===== | ||
The basic data types in AmbientTalk are numbers (i.e. integers), fractions (i.e. double precision floating point numbers), text (i.e. strings), tables (i.e. arrays) and booleans. In fact, instances of these data types are nothing but objects and as such, they respond to a variety of native methods. Objects will be the subject of the next chapter of the tutorial. This section explains the basic data types and includes some examples how to manipulate them. The complete list of methods can be found in the language reference. | The basic data types in AmbientTalk are numbers (i.e. integers), fractions (i.e. double precision floating point numbers), text (i.e. strings), tables (i.e. arrays) and booleans. In fact, instances of these data types are nothing but objects and as such, they respond to a variety of native methods. Objects will be the subject of the next chapter of the tutorial. This section explains the basic data types and includes some examples how to manipulate them. The complete list of methods can be found in the language reference. | ||
+ | |||
+ | |||
==== Numerical data types ==== | ==== Numerical data types ==== | ||
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Numbers also support some useful iterator methods such as: | Numbers also support some useful iterator methods such as: | ||
< | < | ||
- | >6.to: 0 step: 2 do: { |i| system.println(i) } | + | >1.to: 5 do: { |i| system.println(i)} |
+ | 1 | ||
+ | 2 | ||
+ | 3 | ||
+ | 4 | ||
+ | 5 | ||
+ | >1.to: 5 step: 2 do: { |i| system.println(i)} | ||
+ | 1 | ||
+ | 3 | ||
+ | 5 | ||
+ | > | ||
6 | 6 | ||
4 | 4 | ||
2 | 2 | ||
+ | 0 | ||
>> | >> | ||
> | > | ||
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>> | >> | ||
</ | </ | ||
+ | |||
==== Tables ==== | ==== Tables ==== | ||
- | We have already | + | We have already |
< | < | ||
> | > | ||
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>>1 | >>1 | ||
> def [i, j] := [1,3] | > def [i, j] := [1,3] | ||
- | >>>[1, 3] | + | >>[1, 3] |
>{i < j}.whileTrue: | >{i < j}.whileTrue: | ||
1 | 1 | ||
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===== Control Flow Constructs ===== | ===== Control Flow Constructs ===== | ||
- | 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: | + | Control flow constructs are defined in the "lexical root". 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: booleanCondition then: consequent | + | if: booleanCondition then: consequentClosure |
- | if: booleanCondition then: consequent | + | if: booleanCondition then: consequentClosure |
- | while: | + | while: |
- | foreach: | + | foreach: |
- | do: body if: condition | + | do: bodyClosure |
- | do: body unless: condition | + | do: bodyClosure |
</ | </ | ||
- | Note that '' | + | <note warn> |
+ | Note that '' | ||
+ | </ | ||
+ | |||
+ | The above definitions in the lexical root of AmbientTalk are simply convenience functions for the methods defined on booleans and closures. For example, an if-statement can also be encoded as a message send, as in Smalltalk: '' | ||
- | 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 the above structures is shown below in the definition of the sort function. |
< | < | ||
>def sort(table, cmp := { |e1,e2| e1 < e2 }) { | >def sort(table, cmp := { |e1,e2| e1 < e2 }) { | ||
- | def quickSort(table, | + | |
- | def left := low; | + | def left := low; |
- | def right := high; | + | def right := high; |
- | def pivot := table[(left+right) /- 2]; | + | def pivot := table[(left+right) /- 2]; |
- | def save := nil; | + | def save := nil; |
- | while: { left <= right } do: { | + | while: { left <= right } do: { |
- | | + | while: { cmp(table[left], |
- | left := left + 1 | + | left := left + 1 |
- | }; | + | }; |
- | | + | while: { cmp(pivot, table[right]) } do: { |
- | right := right - 1 | + | right := right - 1 |
- | }; | + | }; |
- | | + | if: (left <= right) then: { |
- | | + | // swap elements |
- | | + | save := table[left]; |
- | table[left] := table[right]; | + | table[left] := table[right]; |
- | table[right] := save; | + | table[right] := save; |
- | left := left + 1; | + | left := left + 1; |
- | right := right - 1; | + | right := right - 1; |
- | | + | }; |
- | }; | + | }; |
- | if: (low< | + | if: (low< |
- | if: (high> | + | if: (high> |
- | | + | table; |
- | | + | }; |
- | | + | quickSort(table, |
- | }; | + | }; |
>>< | >>< | ||
> | > | ||
>>[2, 4, 5, 6, 8, 37] | >>[2, 4, 5, 6, 8, 37] | ||
</ | </ | ||
+ | |||
+ | AmbientTalk has no '' |
at/tutorial/basic.txt · Last modified: 2020/02/09 22:05 by elisag