From 754bbf7a25a8dda49b5d08ef0d0443bbf5af0e36 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Sun, 7 Apr 2024 13:41:34 -0500 Subject: new repository --- devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html | 80 ++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) create mode 100644 devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html (limited to 'devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html') diff --git a/devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html b/devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html new file mode 100644 index 00000000..bbc17453 --- /dev/null +++ b/devdocs/c/numeric%2Ffenv%2Ffe_dfl_env.html @@ -0,0 +1,80 @@ +

FE_DFL_ENV

Defined in header <fenv.h> 
#define FE_DFL_ENV  /*implementation defined*/
+		 (since C99)

The macro constant FE_DFL_ENV expands to an expression of type const fenv_t*, which points to a full copy of the default floating-point environment, that is, the environment as loaded at program startup.

+

Additional macros that begin with FE_ followed by uppercase letters, and have the type const fenv_t*, may be supported by an implementation.

+

Example

#include <stdio.h>
+#include <fenv.h>
+ 
+#pragma STDC FENV_ACCESS ON
+ 
+void show_fe_exceptions(void)
+{
+    printf("current exceptions raised: ");
+    if(fetestexcept(FE_DIVBYZERO))     printf(" FE_DIVBYZERO");
+    if(fetestexcept(FE_INEXACT))       printf(" FE_INEXACT");
+    if(fetestexcept(FE_INVALID))       printf(" FE_INVALID");
+    if(fetestexcept(FE_OVERFLOW))      printf(" FE_OVERFLOW");
+    if(fetestexcept(FE_UNDERFLOW))     printf(" FE_UNDERFLOW");
+    if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none");
+    printf("\n");
+}
+ 
+void show_fe_rounding_method(void)
+{
+    printf("current rounding method:    ");
+    switch (fegetround()) {
+           case FE_TONEAREST:  printf ("FE_TONEAREST");  break;
+           case FE_DOWNWARD:   printf ("FE_DOWNWARD");   break;
+           case FE_UPWARD:     printf ("FE_UPWARD");     break;
+           case FE_TOWARDZERO: printf ("FE_TOWARDZERO"); break;
+           default:            printf ("unknown");
+    };
+    printf("\n");
+}
+ 
+void show_fe_environment(void)
+{
+    show_fe_exceptions();
+    show_fe_rounding_method();
+} 
+ 
+int main()
+{
+    printf("On startup:\n");
+    show_fe_environment();
+ 
+    // Change environment
+    fesetround(FE_DOWNWARD);     // change rounding mode
+    feraiseexcept(FE_INVALID);   // raise exception
+    printf("\nBefore restoration:\n");
+    show_fe_environment();
+ 
+    fesetenv(FE_DFL_ENV);    // restore
+    printf("\nAfter restoring default environment:\n");
+    show_fe_environment();
+}

Output:

+
On startup:
+current exceptions raised:  none
+current rounding method:    FE_TONEAREST
+ 
+Before restoration:
+current exceptions raised:  FE_INVALID
+current rounding method:    FE_DOWNWARD
+ 
+After restoring default environment:
+current exceptions raised:  none
+current rounding method:    FE_TONEAREST

References

See also

+ + +
+
(C99)
 saves or restores the current floating-point environment
(function)
+
(C99)
 restores the floating-point environment and raises the previously raise exceptions
(function)
C++ documentation for FE_DFL_ENV
+

+ © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
+ https://en.cppreference.com/w/c/numeric/fenv/FE_DFL_ENV +

+
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