diff options
Diffstat (limited to 'shell/math.c')
| -rw-r--r-- | shell/math.c | 48 |
1 files changed, 34 insertions, 14 deletions
diff --git a/shell/math.c b/shell/math.c index 748c3b3..f6aa02a 100644 --- a/shell/math.c +++ b/shell/math.c @@ -157,17 +157,17 @@ typedef unsigned char operator; #define fix_assignment_prec(prec) do { if (prec == 3) prec = 2; } while (0) /* Ternary conditional operator is right associative too */ -// FIXME: -// bash documentation says that precedence order is: -// ... -// expr ? expr1 : expr2 -// = *= /= %= += -= <<= >>= &= ^= |= -// exprA , exprB -// but in practice, the rules for expr1 and expr2 are different: -// assignments and commas in expr1 have higher precedence than ?:, -// but in expr2 they haven't: -// "v ? 1,2 : 3,4" is parsed as "(v ? (1,2) : 3),4" -// "v ? a=2 : b=4" is parsed as "(v ? (a=1) : b)=4" (thus, this is a syntax error) +/* + * bash documentation says that precedence order is: + * ... + * expr ? expr1 : expr2 + * = *= /= %= += -= <<= >>= &= ^= |= + * exprA , exprB + * What it omits is that expr1 is parsed as if parenthesized + * (this matches the rules of ?: in C language): + * "v ? 1,2 : 3,4" is parsed as "(v ? (1,2) : 3),4" + * "v ? a=2 : b=4" is parsed as "(v ? (a=1) : b)=4" (thus, this is a syntax error) + */ #define TOK_CONDITIONAL tok_decl(4,0) #define TOK_CONDITIONAL_SEP tok_decl(4,1) @@ -629,6 +629,7 @@ evaluate_string(arith_state_t *math_state, const char *expr) /* Stack of operator tokens */ operator *const opstack = alloca(expr_len * sizeof(opstack[0])); operator *opstackptr = opstack; + operator insert_op = 0xff; /* Start with a left paren */ dbg("(%d) op:TOK_LPAREN", (int)(opstackptr - opstack)); @@ -751,11 +752,24 @@ evaluate_string(arith_state_t *math_state, const char *expr) goto err; } } + /* NB: expr now points past the operator */ tok_found: op = p[1]; /* fetch TOK_foo value */ - tok_found1: - /* NB: expr now points past the operator */ + /* Special rule for "? EXPR :" + * "EXPR in the middle of ? : is parsed as if parenthesized" + * (this quirk originates in C grammar, I think). + */ + if (op == TOK_CONDITIONAL) { + insert_op = TOK_LPAREN; + dbg("insert_op=%02x", insert_op); + } + if (op == TOK_CONDITIONAL_SEP) { + insert_op = op; + op = TOK_RPAREN; + dbg("insert_op=%02x op=%02x", insert_op, op); + } + tok_found1: /* post grammar: a++ reduce to num */ if (lasttok == TOK_POST_INC || lasttok == TOK_POST_DEC) lasttok = TOK_NUM; @@ -865,9 +879,15 @@ dbg(" numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[ /* else: LPAREN or UNARY: push it on opstack */ push_op: /* Push this operator to opstack */ - dbg("(%d) op:%02x", (int)(opstackptr - opstack), op); + dbg("(%d) op:%02x insert_op:%02x", (int)(opstackptr - opstack), op, insert_op); *opstackptr++ = lasttok = op; next: ; + if (insert_op != 0xff) { + op = insert_op; + insert_op = 0xff; + dbg("inserting %02x", op); + goto tok_found1; + } } /* while (1) */ err: |