Sollya User's Manual

Name:

== equality test operator

Library name:

sollya_obj_t sollya_lib_cmp_equal(sollya_obj_t, sollya_obj_t)

Usage:

expr1 == expr2 : (any type, any type) -> boolean

Parameters:

expr1 and expr2 represent expressions

Description:

The operator == evaluates to true iff its operands expr1 and expr2 are syntactically equal and different from error or constant expressions that are not constants and that evaluate to the same floating-point number with the global precision prec. The user should be aware of the fact that because of floating-point evaluation, the operator == is not exactly the same as the mathematical equality. Further remark that according to IEEE 754-2008 floating-point rules, which Sollya emulates, floating-point data which are NaN do not compare equal to any other floating-point datum, including NaN.

Example 1:

   > "Hello" == "Hello";
   true
   > "Hello" == "Salut";
   false
   > "Hello" == 5;
   false
   > 5 + x == 5 + x;
   true

Example 2:

   > 1 == exp(0);
   true
   > asin(1) * 2 == pi;
   true
   > exp(5) == log(4);
   false

Example 3:

> sin(pi/6) == 1/4;
false

Example 4:

   > prec = 12;
   The precision has been set to 12 bits.
   > verbosity = 1!;
   > 16384.1 == 16385.1;
   Warning: Rounding occurred when converting the constant "16384.1" to floating-point with 12 bits.
   If safe computation is needed, try to increase the precision.
   Warning: Rounding occurred when converting the constant "16385.1" to floating-point with 12 bits.
   If safe computation is needed, try to increase the precision.
   true

Example 5:

> error == error;
false

Example 6:

   > a = "Biba";
   > b = NaN;
   > a == a;
   true
   > b == b;
   false

See also: !=, >, >=, <=, <, in, !, &&, ||, error, prec

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