site/contents/learn-operators.md
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----- content-type: "page" title: "Learn: Operators" ----- {@ _defs_.md || 0 @} Every min program needs _operators_ to: * Manipulate elements on the stack * Perform operations on data * Provide side effects (read/print to standard input/output/files, etc.) There are two types of operators: _symbols_ and _sigils_. _Symbols_ are the most common type of operator. A min symbol is a single word that is either provided by one of the predefined min {#link-page||reference||modules#} like `dup` or `.` or defined by the user. User-defined symbols must: * Start with a letter or an underscore (\_). * Contain zero or more letters, numbers and/or any of the following characters: `/ ! ? + * . _ -` It is possible to define symbols using the {#link-operator||lang||define#} symbol. The following min program defines a new symbol called square that duplicates the first element on the stack and multiplies the two elements: (dup *) "square" define Besides symbols, you can also define sigila. min provides a set of predefined _sigils_ as abbreviations for for commonly-used symbols. For example, the previous definition could be rewritten as follows using sigils: (dup *) :square A sigil like `:` can be prepended to a double-quoted string or a single word (with no spaces) which will be treated as a string instead of using the corresponding symbol. For example, the following executes the command `ls -al` and pushes the command return code on the atack: !"ls -al"` Currently min provides the following sigils: + : Alias for {#link-operator||lang||module#}. ~ : Alias for {#link-operator||lang||delete#}. ' : Alias for {#link-operator||lang||quote#}. \: : Alias for {#link-operator||lang||define#}. ^ : Alias for {#link-operator||lang||call#}. @ : Alias for {#link-operator||lang||bind#}. > : Alias for {#link-operator||lang||save-symbol#}. < : Alias for {#link-operator||lang||load-symbol#}. = : Alias for {#link-operator||lang||quote-bind#}. \# : Alias for {#link-operator||lang||quote-define#}. / : Alias for {#link-operator||dict||dget#}. % : Alias for {#link-operator||dict||dset#}. ? : Alias for {#link-operator||dict||dhas?#}. ! : Alias for {#link-operator||sys||system#}. & : Alias for {#link-operator||sys||run#}. $ : Alias for {#link-operator||sys||get-env#}. Besides system sigils, you can also create your own sigils. Unlike system sigils however, user defined sigils: * have the same character restricrions as symbols * can only be prepended to double-quoted strings * can be unsealed, deleted, redefined, and sealed. Sigils can be a very powerful construct and a way to reduce boulerplate code: you can define a sigil to use as you would use any symbol which requires a single string or quoted symbol on the stack. Consider the following example: 'from-json 'j define-sigil This will define a `j` sigil that will parse any string as JSON and convert it to its corresponding min representation. {#link-learn||quotations||Quotations#} |