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digitalmars.D.bugs - [Issue 1668] New: std.stream readf can't read int, nan, inf as floats

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1668

           Summary: std.stream readf can't read int, nan, inf as floats
           Product: D
           Version: 1.023
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: wbaxter gmail.com


std.stream readf can't read int, nan, inf as floats.

This means that readf can't read in everything that writef prints out, even if
you know the exact order of elements in the stream.

Here are some tests:

//===========================================================================
module rwnans;
import std.stdio;
import std.stream;

void try_rwop(float x, string fmt="")
{
    writefln("--- Test x=%f", x);
    auto S = new MemoryStream();
    S.writef(fmt, x);
    S.position = 0;
    writefln("S buffer contains '%s'", S.readLine());
    S.position = 0;

    float y;
    int got = S.readf(&y);

    writefln("read %d bytes, got y = %s", got, y);
}

void main()
{
    try_rwop(1.0);
    try_rwop(1.0,"%f");
    float x; // nan
    try_rwop(x);
    try_rwop(x,"%f");
    x = 1.0/0.0 ; // inf
    try_rwop(x);
    try_rwop(x,"%f");

    try_rwop(-x);
    try_rwop(-x,"%f");
}


--
Nov 13 2007
parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=1668






More info.  The failure to parse something like "1" as a float seems to only
happen when there's only a single byte in the stream.  And then parsing as an
int fails too.  

Another bug: if you rewind the stream after failing to parse that as a float,
then the next attempt to parse as an int will get two characters instead of the
one and only one that was in the stream to begin with.

Here's an updated test program:

//===========================================================================

module rwnans;

import std.stdio;
import std.stream;


float try_rwop(float x, string fmt="", string pad="")
{
    writefln("--- Test x=%f", x);
    auto S = new MemoryStream();
    S.writef(fmt, x, pad);
    S.position = 0;
    writefln("S buffer contains '%s'", S.readLine());
    S.position = 0;

    float y;
    int got;
    do {
        got = S.readf(&y);
        writefln("read %d bytes, got y = %s", got, y);
        if (got) break;

        S.position=0;

        // try as integer
        int iy;
        got = S.readf(&iy);
        writefln("read %d bytes as int, got iy = %s", got, iy);
        if(got) break;

        S.position=0;

        // try nan inf,-inf
        got = S.readf("nan");
        if (got) break;

        S.position=0;

        got = S.readf("-inf");
        if (got) break;

        S.position=0;

        got = S.readf("inf");
        if (got) break;

    } while(false);
    if (!got)
        writefln("Couldn't parse it!");
    else
        writefln("finally got y=%s", y);

    return y;
}

void main()
{
    string pad = " ";
    try_rwop(1.0);       // fails!
    try_rwop(1.0,"%f");  // ok
    try_rwop(1.0,"",pad);// ok
    try_rwop(1.0,"%f");

    try_rwop(12.0);      // ok
    try_rwop(12.0,"%f"); // ok

    try_rwop(1.001);     // ok
    try_rwop(1.001,"%f");// ok

    float x; // nan
    try_rwop(x);         // fails!
    try_rwop(x,"%f");    // fails!
    try_rwop(x,"%f",pad);// fails!
    x = 1.0/0.0 ; // inf  
    try_rwop(x);         // fails!
    try_rwop(x,"%f");    // fails!
    try_rwop(x,"%f",pad);// fails!

    try_rwop(-x);        // fails!
    try_rwop(-x,"%f");   // fails!
    try_rwop(x,"%f",pad);// fails!

}


--
Nov 13 2007