'\" t .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk) .\" and Copyright 2008, Linux Foundation, written by Michael Kerrisk .\" .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .\" References consulted: .\" Linux libc source code .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991) .\" 386BSD man pages .\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu) .\" Modified 1995-08-14 by Arnt Gulbrandsen .\" Modified 2002-07-27 by Walter Harms .\" (walter.harms@informatik.uni-oldenburg.de) .\" .TH exp 3 2024-05-02 "Linux man-pages 6.9.1" .SH NAME exp, expf, expl \- base-e exponential function .SH LIBRARY Math library .RI ( libm ", " \-lm ) .SH SYNOPSIS .nf .B #include .P .BI "double exp(double " x ); .BI "float expf(float " x ); .BI "long double expl(long double " x ); .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR expf (), .BR expl (): .nf _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L || /* Since glibc 2.19: */ _DEFAULT_SOURCE || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION These functions return the value of e (the base of natural logarithms) raised to the power of .IR x . .SH RETURN VALUE On success, these functions return the exponential value of .IR x . .P If .I x is a NaN, a NaN is returned. .P If .I x is positive infinity, positive infinity is returned. .P If .I x is negative infinity, +0 is returned. .P If the result underflows, a range error occurs, and zero is returned. .P If the result overflows, a range error occurs, and the functions return .RB + HUGE_VAL , .RB + HUGE_VALF , or .RB + HUGE_VALL , respectively. .SH ERRORS See .BR math_error (7) for information on how to determine whether an error has occurred when calling these functions. .P The following errors can occur: .TP Range error, overflow .I errno is set to .BR ERANGE . An overflow floating-point exception .RB ( FE_OVERFLOW ) is raised. .TP Range error, underflow .I errno is set to .BR ERANGE . An underflow floating-point exception .RB ( FE_UNDERFLOW ) is raised. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR exp (), .BR expf (), .BR expl () T} Thread safety MT-Safe .TE .SH STANDARDS C11, POSIX.1-2008. .SH HISTORY C99, POSIX.1-2001. .P The variant returning .I double also conforms to SVr4, 4.3BSD, C89. .SH SEE ALSO .BR cbrt (3), .BR cexp (3), .BR exp10 (3), .BR exp2 (3), .BR expm1 (3), .BR sqrt (3)