/* Contains code from Marc Feeley's tinyc.c, with permission. */
/* http://www.iro.umontreal.ca/~felipe/IFT2030-Automne2002/Complements/tinyc.c */
/* Heavily modified by Chris Curl to add more C-like support */
/*
* This is a compiler for Tiny-C, a stripped down version of C.
* The compiler reads the program from standard input and prints out
* the value of the variables that are not zero.
* The grammar of Tiny-C in EBNF is:
*
* <program> ::= <global_defs> <function_defs> <main_def>
* <main_def> ::= ("void" | "int") "main" "(" ")" "{" <statement> "}"
* <defs> ::= <def> | <def> <def>
* <def> ::= <func_def> | <var_def>
* <func_def> ::= ("void" | "int") <id> "(" [ <parameter> { "," <parameter> } ] ")" "{" { <statement> } "}"
* <parameter> ::= "int" <id> [ "[" "]" ]
* <local_decl> ::= "int" <id> { "," <id> } ";"
* <var_def> ::= "int" <var_decl> { "," <var_decl> } ";"
* <var_decl> ::= <id> [ "[" <int> "]" ] | <id> "[" [ <int> ] "]" "=" <string>
* <statement> ::= <local_decl> |
* <void_func_call> ";" |
* "return" [ <expr> ] ";" |
* "if" <paren_expr> <statement> |
* "if" <paren_expr> <statement> "else" <statement> |
* "while" <paren_expr> <statement> |
* "do" <statement> "while" <paren_expr> ";" |
* "{" { <statement> } "}" |
* <expr> ";" |
* ";"
* <paren_expr> ::= "(" <expr> ")"
* <expr> ::= <test> | <id> "=" <expr> | <id> "[" <expr> "]" "=" <expr>
* <test> ::= <math> | <math> "<" <math> | <math> ">" <math> | <math> "==" <math> | <math> "!=" <math>
* <math> ::= <term> | <math> <math_op> <term>
* <math_op> ::= "+" | "-" | "*" | "/" | "%"
* <term> ::= <id> | <func_call> | <id> "[" <expr> "]" | <array_ref> | <int> | <char> | <string> | <paren_expr> | "-" <term>
* <func_call> ::= <int_func_id> "(" [ <expr> { "," <expr> } ] ")"
* <void_func_call> ::= <void_func_id> "(" [ <expr> { "," <expr> } ] ")"
* <array_ref> ::= <global_array_id> | <array_parameter_id>
* <int_func_id> and <void_func_id> are IDs of functions with the
* corresponding return type. Void calls are statements, not terms.
* emit(int value) is a built-in VM service that writes the low byte and
* returns the written byte.
* <id> ::= [A-Z|a-z|_][A-Z|a-z|0-9|_]*
* <int> ::= <a_decimal_integer>
* <char> ::= "'" <single_character_or_escape> "'"
* <string> ::= '"' { <string_character_or_escape> } '"'
* Character literals represent the numeric value of one byte; supported escapes
* are '\n', '\r', '\t', '\0', '\e', '\\', '\'', and '\"'.
* String initializers are global integer arrays laid out as [length, ASCII values..., 0].
* The length excludes the final zero; an omitted array size is inferred, and an
* explicit size must fit the length and terminator. Non-ASCII source characters
* are rejected. String escapes are '\n', '\r', '\t', '\0', '\e', '\\', '\'', and '\"'.
* String literals used as array arguments get anonymous global storage.
* String literals are valid only as array arguments or global array initializers.
* Array parameters pass global-array base slots by reference.
* Array indexes are unchecked at runtime.
* The VM service instruction is encoded as SYS followed by a one-byte service ID.
*
* The compiler does a minimal amount of error checking to help
* highlight the structure of the compiler.
*/
