Add page about differences with Solidity

docs/src/SUMMARY.md

@@ -7,4 +7,8 @@
 - [Installation](./installation.md)
 - [Configuration](./configuration.md)
 
+# Guides
+
+- [Differences with Solidity](./differences_with_solidity.md)
+
 # Reference

docs/src/differences_with_solidity.md

@@ -0,0 +1,61 @@
+# Differences with Solidity
+
+Eclair is based on the Solidity syntax but behaves differently in many aspects.
+It is worth nothing that at this point, Eclair only implements a subset of the Solidity language.
+
+This section highlights some of the differences between Eclair and Solidity.
+
+## Static vs dynamic typing
+
+Solidity is statically typed, meaning that the type of each variable must be known at compile time and the compiler will check that the types are used correctly.
+On the other hand, Eclair is not dynamically typed and variables are only checked at runtime. Furthermore, variables do not need to be declared explicitly.
+
+```javascript
+>> a = 1; // a is an integer
+>> a + 2
+3
+>> a + "bar"
+Error: cannot add uint256 and string
+>> a = "foo"; // a is now a string
+>> a + "bar"
+"foobar"
+```
+
+## Scopes
+
+Eclair has a different scoping mechanism compared to Solidity.
+In particular, Eclair only creates a new scope for function, not for blocks.
+This means that the following code will work in Eclair but not in Solidity:
+
+```javascript
+if (true) {
+    a = 1;
+} else {
+    a = 2;
+}
+console.log(a);
+```
+
+However, the following code will not work:
+
+```javascript
+>> function foo() { a = 1; }
+>> console.log(a)
+Error: a is not defined
+```
+
+## First-class functions and types
+
+Internally, almost everything in Eclair returns a value.
+This means that functions and types can be passed around as arguments to other functions.
+For example, the following is valid in Eclair:
+
+```javascript
+>> usdc = ERC20(0xa0b86991c6218b36c1d19d4a2e9eb0ce3606eb48)
+>> usdcBalance = usdc.balanceOf
+>> usdcBalance(0x47ac0Fb4F2D84898e4D9E7b4DaB3C24507a6D503)
+542999999840000
+>> tu16 = type(uint16)
+>> tu16.max
+65535
+```