feat: Storage minimal + fixes (#118)

Author: julio4

src/SUMMARY.md

@@ -6,23 +6,24 @@ Summary
 # Getting Started
   <!-- - [Local environnement setup](./ch00/env_setup.md) -->
   - [Basics of a Starknet contract](./ch00/basics/introduction.md)
-    - [Variables](./ch00/basics/variables.md)
+    - [Storage](./ch00/basics/storage.md)
     - [Constructor](./ch00/basics/constructor.md)
+    - [Variables](./ch00/basics/variables.md)
     - [Visibility and Mutability](./ch00/basics/visibility-mutability.md)
-    - [Counter contract example](./ch00/basics/counter.md)
+    - [Counter Example](./ch00/basics/counter.md)
     - [Mappings](./ch00/basics/mappings.md)
     - [Errors](./ch00/basics/errors.md)
     - [Events](./ch00/basics/events.md)
     - [Storing Custom Types](./ch00/basics/storing-custom-types.md)
     - [Custom types in entrypoints](./ch00/basics/custom-types-in-entrypoints.md)
   - [Deploy and interact with contracts](./ch00/interacting/interacting.md)
-    - [Factory pattern](./ch00/interacting/factory.md)
     - [Contract interfaces and Traits generation](./ch00/interacting/interfaces-traits.md)
     - [Calling other contracts](./ch00/interacting/calling_other_contracts.md)
+    - [Factory pattern](./ch00/interacting/factory.md)
   - [Testing contracts](./ch00/testing/contract-testing.md)
   - [Cairo cheatsheet](./ch00/cairo_cheatsheet/cairo_cheatsheet.md)
     - [Felt](./ch00/cairo_cheatsheet/felt.md)
-    - [Mapping](./ch00/cairo_cheatsheet/mapping.md)
+    - [LegacyMap](./ch00/cairo_cheatsheet/mapping.md)
     - [Arrays](./ch00/cairo_cheatsheet/arrays.md)
     - [Loop](./ch00/cairo_cheatsheet/loop.md)
     - [Match](./ch00/cairo_cheatsheet/match.md)

src/ch00/basics/storage.md

@@ -0,0 +1,20 @@
+# Storage
+
+Here's the most minimal contract you can write in Cairo:
+
+```rust
+{{#include ../../../listings/ch00-getting-started/storage/src/minimal_contract.cairo}}
+```
+
+Storage is a struct annoted with `#[storage]`. Every contract must have one and only one storage.
+It's a key-value store, where each key will be mapped to a storage address of the contract's storage space.
+
+You can define [storage variables](./variables.md#storage-variables) in your contract, and then use them to store and retrieve data.
+```rust
+{{#include ../../../listings/ch00-getting-started/storage/src/contract.cairo}}
+```
+
+> Actually these two contracts have the same underlying sierra program.
+> From the compiler's perspective, the storage variables don't exist until they are used.
+
+You can also read about [storing custom types](./storing-custom-types.md)

src/ch00/basics/variables.md

@@ -6,7 +6,7 @@ There are 3 types of variables in Cairo contracts:
   - declared inside a function
   - not stored on the blockchain
 - Storage
-  - declared in the `Storage` struct of a contract
+  - declared in the [Storage](./storage.md) of a contract
   - can be accessed from one execution to another
 - Global
   - provides information about the blockchain

src/ch01/constant-product-amm.md

@@ -3,7 +3,7 @@
 This is the Cairo adaptation of the [Solidity by example Constant Product AMM](https://solidity-by-example.org/defi/constant-product-amm/).
 
 ```rust
-{{#include ../listings/ch01-applications/constant_product_amm/src/constant_product_amm.cairo:ConstantProductAmmContract}}
+{{#include ../../listings/ch01-applications/constant_product_amm/src/contracts.cairo:ConstantProductAmmContract}}
 ```
 
 Play with this contract in [Remix](https://remix.ethereum.org/?#activate=Starknet&url=https://github.com/NethermindEth/StarknetByExample/blob/main/listings/ch01-applications/constant_product_amm/src/constant_product_amm.cairo).