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# Chapter 17: Functions
Some thinking on function syntax:
Function Types:
```
{ argtype, argtype, ... -> rettype }
```
Leading `{` character denotes the start of a function or function type.
Functions are normal variables and assigned the same way:
```functiontype var = function-typed-expr```
Functions themselves using the same syntax with as types, but filled in:
```
{ int x, int y ->
sqrt(x*x+y*y);
}
```
Used in a declaration statement:
```
// TYPE VAR = EXPR
{flt,flt->flt} dist = { flt x, flt y ->
sqrt(x*x+y*y);
}
```
Because it gets clunky to write the function type, and because it can be
directly inferred from forwards-flow analysis (not even HM) which we're already
doing at parse-time, we add a new variable declaration syntax: "var" - for
auto-inferring variable types. Not allowed in function headers.
```
var dist = { flt x, flt y -> sqrt(x*x*,y*y); }
```
`var` can be used for normal variables as well:
```
// Newtons approximation to the square root
var sqrt = { flt x ->
var guess = x*x/2;
while( 1 ) {
var next = (x/guess + guess)/2;
if( next == guess ) break;
guess = next;
}
guess;
}
```
When inferring pointer types, it will use the `glb` of the initial expression
type, which may not be what you want:
```
struct LLI { LLI? next; int i; };
var head = LLI(); // Want this declared not-null, but GLB will allow null
head = null; // Allowed
```
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