Changes between Version 33 and Version 34 of IR2

Timestamp:

04/28/21 15:04:24 (5 years ago)

Author:

siegel

Comment:

--

IR2

@@ -7 +7 @@
 === Questions ===
 
-1. **Do variables have initial values?**
-  * No, a declared variable must be initialized before it is used.
+1. **Do variables have default initial values?**
+  * No, a declared variable must be initialized before it is used.   Otherwise, the behavior is undefined.
 1. **How do you initialize a variable?**
-  * By assigning a value to it.   For example `n=$new($int);` will assign `n` an arbitrary integer, while `n=0;` will assign the integer `0` to `n.
+  * By assigning a value to it.   For example `n=$new($int);` will assign `n` an arbitrary integer, while `n=0;` will assign the integer `0` to `n`.
 1. **How is an array allocated?**
   * An array variable `a` is declared with a decl such as `T a[];`, and then a statement such as `a=$new(T[n]);` will assign to `a` a new arbitrary array value for an array of length `n` of elements of type `T`.    For heap-allocation, a pointer is declared with a decl such as `T * p;`, and a heap variable is also declared somewhere with a decl such as `$heap heap;` and then a statement such as `p = $alloc(&heap, n, T);` will add a new object to the heap and return a pointer to the first element.  An `$alloc`-ed object can be deallocated with `$free(p);`.
+1. **Is there an "array-pointer pun", as in C?**
+  * No, if you want a pointer to element 0 of an array, you have to explicitly say something like `&a[0]`.
 1. **How to you translate between sequences and arrays?**
 1. Can you make types values? (reification)
@@ -98 +100 @@
 direct-declarator:
     ID  /* variable being declared */
-  | direct-declarator '[' ']'  /* array of ... */
+  | direct-declarator '[' expr? ']'  /* array of ... */
   | direct-declarator  '(' type-list? ')'  /* function consuming ... and returning ... */
   | '(' declarator ')'
@@ -104 +106 @@
 type-name: ... /* same as declarator but without the ID */
 type-list: type-name (',' type-name)* ;
-complete-type-name: ... /* same as declarator except '[' expr ']' */
 
 }}}