125 lines
3.4 KiB
Markdown
125 lines
3.4 KiB
Markdown
---
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id: constants-and-variables
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title: Constants & Variables
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---
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The next building block after types are constants and variables.
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## Constants
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Constants are immutable by design, which means their values can't be reassigned.
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When defining a constant you need to provide a `name`, `type` and a `value`:
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<!--DOCUSAURUS_CODE_TABS-->
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<!--Pascaligo-->
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```pascaligo
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const age : int = 25;
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```
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You can evaluate the constant definition above using the following CLI command:
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```shell
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ligo evaluate-value -s pascaligo gitlab-pages/docs/language-basics/src/variables-and-constants/const.ligo age
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# Outputs: 25
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```
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<!--CameLIGO-->
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```cameligo
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let age: int = 25
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```
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You can evaluate the constant definition above using the following CLI command:
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```shell
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ligo evaluate-value -s cameligo gitlab-pages/docs/language-basics/src/variables-and-constants/const.mligo age
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# Outputs: 25
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```
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<!--ReasonLIGO-->
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```reasonligo
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let age: int = 25;
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```
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You can evaluate the constant definition above using the following CLI command:
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```shell
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ligo evaluate-value -s reasonligo gitlab-pages/docs/language-basics/src/variables-and-constants/const.religo age
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# Outputs: 25
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```
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<!--END_DOCUSAURUS_CODE_TABS-->
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## Variables
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<!--DOCUSAURUS_CODE_TABS-->
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<!--Pascaligo-->
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Variables, unlike constants, are mutable. They can't be used in a *global scope*, but they can be used within functions, or function arguments.
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> 💡 Don't worry if you don't understand the function syntax yet. We'll get to it in upcoming sections of the docs.
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> ⚠️ Please be wary that mutation only works within the function scope itself, values outside of the function scope will not be affected.
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```pascaligo
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// won't work, use const for global values instead
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// var four: int = 4;
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function add(const a: int; const b: int) : int is
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block {
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var c : int := a + b;
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} with c
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```
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> ⚠️ Notice the different assignment operator `:=`
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You can run the `add` function defined above using the LIGO compiler like this:
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```shell
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ligo run-function -s pascaligo gitlab-pages/docs/language-basics/src/variables-and-constants/add.ligo add '(1,1)'
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# Outputs: 2
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```
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<!--CameLIGO-->
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As expected from a functional language, CameLIGO uses value-binding
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for variables rather than assignment. Variables are changed by replacement,
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with a new value being bound in place of the old one.
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> 💡 Don't worry if you don't understand the function syntax yet. We'll get to it in upcoming sections of the docs.
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```cameligo
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let add (a: int) (b: int) : int =
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let c : int = a + b in c
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```
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You can run the `add` function defined above using the LIGO compiler like this:
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```shell
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ligo run-function -s cameligo gitlab-pages/docs/language-basics/src/variables-and-constants/add.mligo add '(1,1)'
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# Outputs: 2
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```
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<!--ReasonLIGO-->
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As expected from a functional language, ReasonLIGO uses value-binding
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for variables rather than assignment. Variables are changed by replacement,
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with a new value being bound in place of the old one.
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> 💡 Don't worry if you don't understand the function syntax yet. We'll get to it in upcoming sections of the docs.
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```reasonligo
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let add = ((a,b): (int, int)): int => {
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let c: int = a + b;
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c;
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};
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```
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You can run the `add` function defined above using the LIGO compiler like this:
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```shell
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ligo run-function -s reasonligo gitlab-pages/docs/language-basics/src/variables-and-constants/add.religo add '(1,1)'
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# Outputs: 2
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```
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<!--END_DOCUSAURUS_CODE_TABS-->
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