Other Alias
atan, _atan2, _atanpi, _atan2pi

gentype atan(gentype y_over_x);

gentype atan2(gentype y, gentype x);

gentype atanh(gentype );

gentype atanpi(gentype x);

gentype atan2pi(gentype y, gentype x);
DESCRIPTION
atan
atan2 is the arc tangent of y / x.
atanh is the hyperbolic arc tangent function.
atanpi computes atan (x) / π.
atan2pi computes atan2 (y, x) / π.
NOTES
The vector versions of the math functions operate componentwise. The description is percomponent.
The builtin math functions are not affected by the prevailing rounding mode in the calling environment, and always return the same value as they would if called with the round to nearest even rounding mode.
The builtin math functions take scalar or vector arguments. For any specific use of these function, the actual type has to be the same for all arguments and the return type unless otherwise specified.
The generic type name gentype is used to indicate that the function can take float, float2, float3, float4, float8, float16, double, double2, double3, double4, double8, or double16 as the type for the arguments.
If extended with cl_khr_fp16(3clc), generic type name gentype may indicate half and half{234816} as arguments and return values.
The generic type name gentypef is used to indicate that the function can take float, float2, float3, float4, float8, or float16 as the type for the arguments.
The generic type name gentyped is used to indicate that the function can take double, double2, double3, double4, double8, or double16 as the type for the arguments.
SPECIFICATION
m[blue]OpenCL Specificationm[][1]
AUTHORS
The Khronos Group
COPYRIGHT
Copyright © 20072011 The Khronos Group Inc.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.
NOTES
 1.

OpenCL Specification
 page 244, section 6.12.2  Math Functions