## digitalmars.D.learn - Issue with template constraints in numeric types

- data pulverizer (35/35) Aug 03 Dear all,
- data pulverizer (4/6) Aug 03 That is T test(T: double)(T x, T y){...} and T test(T)(T x, T
- Adam D. Ruppe (7/9) Aug 03 Are you familiar with isFloatingPoint?
- data pulverizer (18/28) Aug 03 Thank you very much!
- data pulverizer (4/20) Aug 03 Hmm ... it looks as the specialization `:` operator is working
- jmh530 (2/5) Aug 04 They're both doing the same thing as far as I know.

Dear all, I am writing template constraints for different numeric types: ``` import std.stdio: writeln; import std.traits: isIntegral, isNumeric; T test(T)(T x, T y) if(is(T: double) && isNumeric!T) { return x*y; } auto test(T)(T x, T y) if(!is(T: double) && isNumeric!T) { return 5*test!double(x, y); } void main() { int x = 2; double y = 2.0; writeln("int test: ", test(x, x)); writeln("double test: ", test(y, y)); } ``` returns: ``` int test: 4 double test: 4 ``` The same issue occurs when I try using template specializations instead. Explanations and suggestions please. Thank you! Compiler details: $ dmd --version DMD64 D Compiler v2.074.1 Copyright (c) 1999-2017 by Digital Mars written by Walter Bright

Aug 03

On Thursday, 3 August 2017 at 12:24:02 UTC, data pulverizer wrote:The same issue occurs when I try using template specializations instead. ...That is T test(T: double)(T x, T y){...} and T test(T)(T x, T y){...} Thanks

Aug 03

On Thursday, 3 August 2017 at 12:24:02 UTC, data pulverizer wrote:import std.traits: isIntegral, isNumeric;Are you familiar with isFloatingPoint? http://dpldocs.info/experimental-docs/std.traits.isFloatingPoint.htmlif(is(T: double) && isNumeric!T)Keep in mind that T:double here means "if T can implicitly convert to double". Since int can implicitly convert to double too, this case covers both families! You might want to try == instead of : for a more exact match.

Aug 03

On Thursday, 3 August 2017 at 12:31:00 UTC, Adam D. Ruppe wrote:On Thursday, 3 August 2017 at 12:24:02 UTC, data pulverizer wrote:Thank you very much! What about this case: ``` T test(T: double)(T x, T y) { return x*y; } auto test(T)(T x, T y) { return 5*test!double(x, y); } ``` which also gives: ``` int test: 4 double test: 4 ```import std.traits: isIntegral, isNumeric;Are you familiar with isFloatingPoint? http://dpldocs.info/experimental-docs/std.traits.isFloatingPoint.htmlif(is(T: double) && isNumeric!T)Keep in mind that T:double here means "if T can implicitly convert to double". Since int can implicitly convert to double too, this case covers both families! You might want to try == instead of : for a more exact match.

Aug 03

On Thursday, 3 August 2017 at 12:35:08 UTC, data pulverizer wrote:What about this case: ``` T test(T: double)(T x, T y) { return x*y; } auto test(T)(T x, T y) { return 5*test!double(x, y); } ``` which also gives: ``` int test: 4 double test: 4 ```Hmm ... it looks as the specialization `:` operator is working like the constraint `:` operator and doing convertible at least for the floating point case. Is that right?

Aug 03

On Thursday, 3 August 2017 at 12:49:48 UTC, data pulverizer wrote:Hmm ... it looks as the specialization `:` operator is working like the constraint `:` operator and doing convertible at least for the floating point case. Is that right?They're both doing the same thing as far as I know.

Aug 04