github.com/xiaq/elvish@v0.12.0/website/src/ref/philosophy.md (about)

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     2  
     3  The development of Elvish is driven by a set of ideas, a **design philosophy**.
     4  
     5  # The language
     6  
     7  *   Elvish should be a real, expressive programming language.
     8  
     9      Shells are often considered domain-specific languages (DSL), but Elvish
    10      does not restrict itself to this notion. It embraces such concepts as
    11      namespaces, first-class functions and exceptions. Whatever you may find in
    12      a modern general-purpose programming language is likely to be found in
    13      Elvish.
    14  
    15      Elvish is not alone in this respect. There are multiple ongoing efforts;
    16      [this page](https://github.com/oilshell/oil/wiki/ExternalResources) on
    17      the wiki of oilshell (which is one of the efforts) is a good reference.
    18  
    19  *   Elvish should try to preserve and extend traditional shell programming
    20      techniques, as long as they don't conflict with the previous tenet. Some
    21      examples are:
    22  
    23      *   Barewords are simply strings.
    24  
    25      *   Prefix notation dominates, like Lisp. For example, arithmetics is done
    26          like `+ 10 (/ 105 5)`.
    27  
    28      *   Pipeline is the main tool for function composition. To make pipelines
    29          suitable for complex data manipulation, Elvish extends them to be able
    30          to carry structured data (as opposed to just bytes).
    31  
    32      *   Output capture is the auxiliary tool for function composition. Elvish
    33          functions may write structured data directly to the output, and
    34          capturing the output yields the same structured data.
    35  
    36  # The user interface
    37  
    38  *   The user interface should be usable without any customizations. It should
    39      be simple and consistent by default:
    40  
    41      *   Prefer to extend well-known functionalities in other shell to inventing
    42          brand new ones. For instance, in Elvish Ctrl-R summons the "history
    43          listing" for searching history, akin to how Ctrl-R works in bash, but
    44          more powerful.
    45  
    46      *   When a useful feature has no prior art in other shells, borrow from
    47          other programs. For instance, the [navigation
    48          mode](/learn/cookbook.html#navigation-mode), summoned by Ctrl-N,
    49          mimics [Ranger](http://ranger.nongnu.org); while the "location mode"
    50          used for quickly changing location, mimics location bars in GUI
    51          browsers (and is summoned by the same key combination Ctrl-L).
    52  
    53  *   Customizability should be achieved via progammability, not an enormous
    54      inventory of options that interact with each other in obscure ways.