On 10/26/2011 06:42 PM, Paul Berry wrote:
> In order to implement the GLSL 1.30 isinf() function, it will be
> necessary to be able to represent infinity in the GLSL IR s-expression
> format. This patch extends the s-expression parser so that it treats
> the string "#inf" as a floating point value representing positive
> infinity.
> ---
> src/glsl/s_expression.cpp | 33 +++++++++++++++++++--------------
> 1 files changed, 19 insertions(+), 14 deletions(-)
Two kind of stupid comments:
Scheme represents infinity as +inf.0 or -inf.0 and NaN as +nan.0. If
you wanted to be more Scheme-like, you could do that (and also gain a
representation of -infinity if you wanted...)
Also...strtod() already accepts "INF"/"INFINITY" and "NAN" for these
cases. Which actually kind of sucks because somebody could totally name
their variables that (unlike #inf or +inf.0).
That should be fixed someday. But there are a lot of things the reader
can't do (like structs), so...not terribly important. It works well
enough for now and we can always fix it when it actually matters.
So, I guess you've got a few options:
1. Keep patch as is (#inf)
2. Switch to +inf.0, -inf.0, +nan.0 to be like Scheme
3. Drop this patch and just use INFINITY in the built-in files.
I'm honestly okay with any of these. For the series:
Reviewed-by: Kenneth Graunke <kenn...@whitecape.org>
> diff --git a/src/glsl/s_expression.cpp b/src/glsl/s_expression.cpp
> index e704a3b..4391488 100644
> --- a/src/glsl/s_expression.cpp
> +++ b/src/glsl/s_expression.cpp
> @@ -64,21 +64,26 @@ read_atom(void *ctx, const char *&src, char
> *&symbol_buffer)
> if (n == 0)
> return NULL; // no atom
>
> - // Check if the atom is a number.
> - char *float_end = NULL;
> - double f = glsl_strtod(src, &float_end);
> - if (float_end != src) {
> - char *int_end = NULL;
> - int i = strtol(src, &int_end, 10);
> - // If strtod matched more characters, it must have a decimal part
> - if (float_end > int_end)
> - expr = new(ctx) s_float(f);
> - else
> - expr = new(ctx) s_int(i);
> + // Check for the special symbol '#inf', which means +Infinity
> + if (n == 4 && strncmp(src, "#inf", 4) == 0) {
> + expr = new(ctx) s_float(INFINITY);
> } else {
> - // Not a number; return a symbol.
> - symbol_buffer[n] = '\0';
> - expr = new(ctx) s_symbol(symbol_buffer, n);
> + // Check if the atom is a number.
> + char *float_end = NULL;
> + double f = glsl_strtod(src, &float_end);
> + if (float_end != src) {
> + char *int_end = NULL;
> + int i = strtol(src, &int_end, 10);
> + // If strtod matched more characters, it must have a decimal part
> + if (float_end > int_end)
> + expr = new(ctx) s_float(f);
> + else
> + expr = new(ctx) s_int(i);
> + } else {
> + // Not a number; return a symbol.
> + symbol_buffer[n] = '\0';
> + expr = new(ctx) s_symbol(symbol_buffer, n);
> + }
> }
>
> src += n;
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