Category:Lambdatalk: Difference between revisions

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2) {lambda talk}, a purely functional language unifying authoring, styling and scripting in a single and coherent s-expression based syntax.

=={lambda talk} in few words==

=={lambda talk} in a few words==

1) Expressions are written in a prefix notation using curly braces.

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-> 2+3 is equal to 5

• 3) Functions are created with '''lambda''' and named with '''def'''.

3) Functions are created with '''lambda''' and named with '''def'''.

{def foo

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==more about {lambda talk}==

{lambda talk} is freely inspired by the λ-calculus. At the lowest level a {lambda talk} expression is exclusively made of words, abstractions and applications:

{lambda talk} is freely inspired by the '''λ-calculus''. At the lowest level a {lambda talk} expression is exclusively made of words, abstractions and applications:

===structure & evaluation===

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{def word expression}

allowing to create constants added to the dictionary and give names to anonymous functions.

allowing to create constants added to the dictionary and to give names to anonymous functions.

What can be done with so little?

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{def CDR {lambda {:z} {:z {lambda {:x :y} :y}}}} -> CDR

{CAR {CONS Hello World}} -> Hello

{~~CAR~~ {CONS Hello World}} -> World

{CDR {CONS Hello World}} -> World

===about the implementation===

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};

Using a single '''regular expression''' the eval_forms() function loops over the code string, skips the words out of curly braces, matches nested forms {first rest} from inside out, and replaces them by words. The repeated substitutions inside the code string overcomes limitations of regular language. It's a kind of Turing machine.

'''1) eval_forms()''': Using a single '''regular expression''' the eval_forms() function loops over the code string, skips the words out of curly braces, matches nested forms {first rest} from inside out, and replaces them by words. The repeated substitutions inside the code string overcomes limitations of regular language. It's a kind of Turing machine.

~~The~~ eval_lambdas() function uses arguments as '''regular expressions''' to successively replace occurrences found in the function's body by the given values. Lambdas have the following properties:

'''2) eval_lambdas()''': this function uses arguments as '''regular expressions''' to successively replace occurrences found in the function's body by the given values. Lambdas have the following properties:

- lambdas are '''first class functions''', they can be called as functions' arguments and returned from functions,

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- lambdas accept de facto '''partial function application''': called with a number of values lesser than its arity, a lambda memorizes the given values and returns a new lambda waiting for the rest.

'''Note:''': This is what Ward Cunningham wrote about that: ''« I was surprised that the technique worked so well in so many cases. I knew that regex are highly optimized and the cpus themselves optimize sequential access to memory which the regex must have at its core. [..] Yes, this has at its heart the repeated application of a text transformation. The fact that it is repeated application of the same transformation makes it exceptional. [..] Repeated application of Regular Expressions can perform Touring Complete computations. This works because the needed "state" is in the partially evaluated text itself. »'' All is said!

===and?===