Merge pull request #30 from tesivo/master

Corrections

Author: lotabout

tutorial/en/1-Skeleton.md

@@ -1,7 +1,7 @@
 In this chapter we will have an overview of the compiler's structure.
 
 Before we start, I'd like to restress that it is **interperter** that we want
-to build. That means we can run a C source file just lik a script. It is
+to build. That means we can run a C source file just like a script. It is
 chosen mainly for two reasons:
 
 1. Interpreter differs from Compiler only in code generation phase, thus we'll
@@ -41,7 +41,7 @@ Modeling after c4, our compiler includes 4 main functions:
 1. `next()` for lexical analysis; get the next token; will ignore spaces tabs
    etc.
 2. `program()` main entrance for parser.
-3. `expression(level)`: parse expression; level will be explained in later
+3. `expression(level)`: parser expression; level will be explained in later
    chapter.
 4. `eval()`: the entrance for virtual machine; used to interpret target
    instructions.
@@ -57,6 +57,7 @@ The code is as following:
 #include <stdlib.h>
 #include <memory.h>
 #include <string.h>
+#define int long long // work with 64bit target
 
 int token;            // current token
 char *src, *old_src;  // pointer to source code string;

tutorial/en/2-Virtual-Machine.md

@@ -223,6 +223,7 @@ Let's implement it in the `eval` function:
 void eval() {
     int op, *tmp;
     while (1) {
+        op = *pc++; // get next operation code
         if (op == IMM)       {ax = *pc++;}                                     // load immediate value to ax
         else if (op == LC)   {ax = *(char *)ax;}                               // load character to ax, address in ax
         else if (op == LI)   {ax = *(int *)ax;}                                // load integer to ax, address in ax
@@ -302,7 +303,7 @@ We've commented out `RET` because we'll replace it with `LEV` later.
 In practice the compiler should deal with more: how to pass the arguments to
 a function? How to return the data from the function?
 
-Our convention here about returning value is to store it into `AX` no mater
+Our convention here about returning value is to store it into `AX` no matter
 you're returning a value or a memory address. Then how about argument?
 
 Different language has different convension, here is the standard for C:

tutorial/en/3-Lexer.md

@@ -18,7 +18,7 @@ Let's first look at the structure of a compiler:
 ```
 
 The Compiler can be treated as a transformer that transform C source code into
-assembly. In this sense, lexer can parser are transformers as well: Lexer
+assembly. In this sense, lexer and parser are transformers as well: Lexer
 takes C source code as input and output token stream; Parser will consume the
 token stream and generate assembly code.
 
@@ -519,7 +519,7 @@ information. In the main function, add the following:
 // types of variable/function
 enum { CHAR, INT, PTR };
 int *idmain;                  // the `main` function
-void main() {
+int main(int argc, char **argv) {
     ...
 
     src = "char else enum if int return sizeof while "
@@ -547,6 +547,7 @@ void main() {
 
     ...
     program();
+    return eval();
 }
 ```
 

tutorial/en/4-Top-down-Parsing.md

@@ -110,7 +110,7 @@ As you can see, function `expr` will never exit! In the grammar,
 non-terminator `<expr>` is used recursively and appears immediately after
 `::=` which causes left-recursion.
 
-Lucily, most left-recursive grammers (maybe all? I don't remember) can be
+Luckly, most left-recursive grammers (maybe all? I don't remember) can be
 properly transformed into non left-recursive equivalent ones. Our grammar for
 calculator can be converted into: