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no more if expressions.

This commit is contained in:
Roberto Ierusalimschy 1999-03-11 16:00:12 -03:00
parent 82ad0d5770
commit c454dc7bdd
2 changed files with 10 additions and 36 deletions
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31
lparser.c
View File

@ -1,5 +1,5 @@
/*
** $Id: lparser.c,v 1.27 1999/03/05 21:16:07 roberto Exp roberto $
** $Id: lparser.c,v 1.28 1999/03/10 14:09:45 roberto Exp roberto $
** LL(1) Parser and code generator for Lua
** See Copyright Notice in lua.h
*/
@ -118,7 +118,7 @@ static void exp1 (LexState *ls);
static void exp2 (LexState *ls, vardesc *v);
static void explist (LexState *ls, listdesc *e);
static void explist1 (LexState *ls, listdesc *e);
static void ifpart (LexState *ls, int isexp, int line);
static void ifpart (LexState *ls, int line);
static void parlist (LexState *ls);
static void part (LexState *ls, constdesc *cd);
static void recfield (LexState *ls);
@ -684,7 +684,7 @@ static int stat (LexState *ls) {
FuncState *fs = ls->fs;
switch (ls->token) {
case IF: /* stat -> IF ifpart END */
ifpart(ls, 0, line);
ifpart(ls, line);
return 1;
case WHILE: { /* stat -> WHILE cond DO block END */
@ -833,31 +833,20 @@ static void body (LexState *ls, int needself, int line) {
}
static void ifpart (LexState *ls, int isexp, int line) {
static void ifpart (LexState *ls, int line) {
/* ifpart -> cond THEN block [ELSE block | ELSEIF ifpart] */
/* ifpart -> cond THEN exp [ELSE exp | ELSEIF ifpart] */
int c;
int e;
next(ls); /* skip IF or ELSEIF */
c = cond(ls);
check(ls, THEN);
if (isexp) {
exp1(ls);
deltastack(ls, -1); /* only 'then' x-or 'else' will stay on the stack */
}
else block(ls);
block(ls);
e = SaveWord(ls);
if (ls->token == ELSEIF)
ifpart(ls, isexp, line);
ifpart(ls, line);
else {
int elsepart = optional(ls, ELSE);
if (!isexp) {
if (elsepart) block(ls);
}
else { /* is exp */
if (elsepart) exp1(ls);
else adjuststack(ls, -1); /* empty else exp -> push nil */
}
if (optional(ls, ELSE))
block(ls);
check_match(ls, END, IF, line);
}
codeIf(ls, c, e);
@ -991,10 +980,6 @@ static void simpleexp (LexState *ls, vardesc *v, stack_op *s) {
body(ls, 0, ls->linenumber);
break;
case IF: /* simpleexp -> IF ifpart END */
ifpart(ls, 1, ls->linenumber);
break;
case '(': /* simpleexp -> '(' exp0 ')' */
next(ls);
exp0(ls, v);

15
manual.tex
View File

@ -1,4 +1,4 @@
% $Id: manual.tex,v 1.25 1999/03/04 21:23:39 roberto Exp roberto $
% $Id: manual.tex,v 1.26 1999/03/10 14:09:45 roberto Exp roberto $
\documentclass[11pt]{article}
\usepackage{fullpage,bnf}
@ -41,7 +41,7 @@ Waldemar Celes
\tecgraf\ --- Computer Science Department --- PUC-Rio
}
%\date{\small \verb$Date: 1999/03/04 21:23:39 $}
%\date{\small \verb$Date: 1999/03/10 14:09:45 $}
\maketitle
@ -686,17 +686,6 @@ All binary operators are left associative,
except for \verb|^| (exponentiation),
which is right associative.
\subsubsection{If Expressions}
\begin{Produc}
\produc{exp}{\rwd{if} exp1 \rwd{then} exp1
\rep{\rwd{elseif} exp1 \rwd{then} exp1}
\opt{\rwd{else} exp1} \rwd{end}}
\end{Produc}%
An \Index{if expression} chooses an expression to evaluate
according to its condition.
Its final value is the value of the chosen expression.
An absent else-part is equivalent to \verb|else nil|.
\subsubsection{Table Constructors} \label{tableconstructor}
Table \Index{constructors} are expressions that create tables;
every time a constructor is evaluated, a new table is created.